Polka-dotted treasures: Revising a clade of ascidian- and bivalve-associated shrimps (Caridea: Palaemonidae)

Introduction

The shrimp family Palaemonidae (Crustacea: Decapoda: Caridea) includes a large number of ecto- and endosymbiotic lineages (Kou et al., 2015; Horká et al., 2016; Chow et al., 2021). Its species are known to be associated with hosts belonging to a wide variety of invertebrate taxa, including echinoderms, cnidarians, sponges, molluscs, and ascidians (e.g., Bruce, 1976a; Horká et al., 2016; Chow et al., 2021). Two lineages are known to consist of symbionts that live either inside solitary ascidians or bivalve molluscs, and in one instance of a gastropod mollusc (Bruce, 1995; Fransen, 2002). Most shrimp species within these lineages seem to be characterised by a set of morphological features that appear to be linked to their cryptic lifestyle, including: (1) reduced frontal, dorsal and lateral protrusions for easier movement within the host (e.g., shortening of the rostrum, reduction of the number of rostral teeth, absence or reduction of the antennal and hepatic spines); (2) the development of scales and microsetae on the dactyls of ambulatory pereiopods to increase grip; (3) an adaptive (often cryptic) colouration; (4) a roughly cylindrical body shape with a body size that is adapted to the dimensions of the host’s body cavity; and (5) differences in eye morphology (de Gier et al., 2022 and references herein). In addition, Bruce (1972a) mentions bivalve-associated shrimps bear bigger claws on their second chelipeds, possibly caused by intraspecific competition. There are numerous other crustacean clades bearing similar morphological characters, which are thought to result from their endosymbiotic lifestyle. This is the case for the palaemonid genus Periclimenaeus Borradaile, 1915, associated with colonial ascidians and sponges (Fransen, 2006), and ascidian and mollusc-associated alpheid shrimps (e.g., Betaeus harfordi (Kingsley, 1878) and Synalpheus herdmaniae Lebour, 1938; see Lebour, 1938; Jensen, 1995). In addition, various symbiotic leucothoid amphipods (Vader, 1983) and most pinnotherine pea crabs (de Gier & Becker, 2020) show adaptive features related to a life within a host.

The two lineages mentioned above were defined by large-scale (molecular) phylogenetic studies (Kou et al., 2015; Horká et al., 2016 (parts of clades 5 and 6); Chow et al., 2021 (parts of clades iiic and iiih)). The lineage including the larger genera Ascidonia Fransen, 2002, Conchodytes Peters, 1852, Dactylonia Fransen, 2002, Odontonia Fransen, 2002, and Pontonia Latreille, 1829 (together with smaller related genera) was studied in detail by combining both morphological and molecular data, which showed monophyly in both the studied genera and the entire ingroup (de Gier et al., 2022). The other, smaller lineage consists of four genera, which are characterized by a conspicuous polka-dotted colouration: Anchistus Borradaile, 1898, Dasella Lebour, 1945, Neoanchistus Bruce, 1975, and Paranchistus Holthuis, 1952. Members of Anchistus, Neoanchistus, and Paranchistus are all reported as endosymbionts, associated with bivalve molluscs, such as giant clams, fan shells, scallops, oysters and spiny oysters (Fransen, 1994a; De Grave, 1999). Species of Dasella are endosymbionts of large solitary ascidians (Bruce, 1981a, 2003a; Berggren, 1990). Species of these genera can be found in the Indo-West Pacific region. A revision of the taxa in this clade, including morphological diagnoses, keys, colour descriptions, host ranges, and geographical distribution is provided in the systematic account below.

Although various members of Anchistus and Paranchistus (both s.l.) have been studied for their ecological role (Johnson & Liang, 1966), mating systems and lifecycles (Baeza et al., 2013; Ghory & Kazmi, 2018), or the characterisation of their symbioses (De Grave et al., 2021), the systematic positions of its species remain elusive. While the four genera are known to be closely related (Horká et al., 2016; Chow et al., 2021), true monophyly of the clade (including all members), has not been proven yet. In addition, Chow et al. (2021) showed that the placement of species attributed to Paranchistus was polyphyletic. They recognized two distinct lineages, placing an unknown species of Paranchistus and Paranchistus pycnodontae Bruce, 1978 away from Paranchistus ornatus Holthuis, 1952. In this study, we revise the four genera and aim to construct a more robust phylogeny, parallel to the study of de Gier et al. (2022).

Host switching, an evolutionary process of a symbiotic lineage shifting from one host to another, has been a major topic in marine palaemonid shrimp phylogenetics (Horká et al., 2016; Chow et al., 2021). While lineages of ectosymbiotic palaemonids seem to switch commonly between genera or families, ascidian- and mollusc-associated species have been proven to have switched between entire phyla: the common ancestor of the before-mentioned clade containing the (mostly) bivalve-associated genera Conchodytes and Pontonia, as well as the predominantly ascidian-associated genera Ascidonia, Dactylonia, and Odontonia, was recovered as an ascidian-associated species. Within the clade, at least six different interphyla host switches were recognized, with Odontonia and Notopontonia Bruce, 1991 switching back to an ascidian host affiliation after an ancestral switch from an ascidian- to a bivalve host within the clade consisting of Conchodytes, Odontonia, and related genera (de Gier et al., 2022). We aim to detect possible host switches in the currently studied clade and recover the host of its common ancestor.

Material and methods

Phylogeny reconstructions and ancestral character state analysis

Sequence alignments were obtained using the ClustalW (Thompson et al., 1994) algorithm (default settings) in mega v10.2.5. (Kumar et al., 2018). Ends of the coi and 16S alignments were trimmed manually in mega to 582 bp and 426 bp respectively. The alignment of the protein-coding gene coi was subjected to Xia’s test of nucleotide substitution saturation (Xia et al., 2003) in dambe v7.3.0. (Xia, 2009). None of the codon positions of coi was found to be saturated and thus no data was excluded. After alignment, the non-coding ribosomal 16S gene was examined for highly divergent blocks using Gblocks v0.91b (Talavera & Castresana, 2007) using default parameters but allowing gap positions and smaller finer blocks. Additionally, the settings were changed to allow less strict flanking positions. This resulted in the retention of all bases in the alignment.

Both coi and 16S were analysed individually, and a complement dataset was made for all specimens where both gene sequences were obtained or already available (coi+16S). A concatenated dataset containing both genes was also constructed in mega, to also include specimens where only one of the two sequences was obtained. This alignment consisted of 43 sequences and 1008 positions. A Total Evidence (te) analysis was performed by combining all data from the concatenated alignment and the morphological dataset, to include all ingroup species in the resulting phylogenetic trees.

Models for sequence evolution were calculated in mega using default settings (table 1). Best models were chosen based on values for the Akaike Information Criterion (aic) and Bayesian Information Criterion (bic).

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Phylogenetic analyses were performed under the maximum likelihood (ml) and Bayesian Inference (bi) criteria using RAxML via the on-line cipres (Miller et al., 2010) with the RAxML-NG BlackBox v1.0.0 tool (Kozlov et al., 2019) and MrBayes v3.2.7 (Ronquist & Huelsenbeck, 2003), respectively. For the single-gene ml analyses default settings were used and automatic bootstrapping with a cut-off of 0.03, under an unpartitioned model. The dual-gene alignment used a partitioned model for both genes, with scaled branch length linkage and automatic bootstrapping with a cut-off of 0.03. Consequently, the concatenated dataset used a similar partitioned method. The bi analyses were conducted using a Markov Chain Monte Carlo (mcmc) method with two independent runs and four chains. Analyses were run with a minimum of 5,000,000 generations to ensure that the average standard deviation of split frequencies (asdsf) reached a value < 0.01, which would indicate that the two runs have converged to a stationary distribution. Trees were sampled each 500 generations. The initial 25% of trees was discarded as burn-in and the remaining trees were used to generate consensus trees and to estimate Bayesian posterior probabilities (pp). In all instances, the topology of the bi analyses was displayed in the results, with annotations to the Bayesian posterior probabilities and ml RAxML values at each intraspecific node.

The analysed sequences resulted in four phylogeny reconstructions: the single gene (coi, 16S) and dual gene (coi+16S) phylogeny reconstructions can be found in the appendices (supplementary figs. S1–S3); the concatenated alignment resulted in the phylogeny reconstruction presented in the results section below.

The Total Evidence analyses were performed similar to the phylogenetic analyses of the concatenated alignment, but with the addition of morphological data. The integrative dataset consisted of 52 taxa and 1043 codon/character positions. The following species were only represented by morphological data: Anchistus gravieri Kemp, 1922, Tympanicheles pectinis (Kemp, 1925) comb. nov. (was Anchistus pectinis), Dasella ansoni Bruce, 1983, Dasella brucei Berggren, 1990, Neoanchistus cardiodytes Bruce, 1975, Neoanchistus nasalis Holthuis, 1986, Polkamenes liui (Li, Bruce & R.B. Manning, 2004) comb. nov. (was Paranchistus liui), Polkamenes nobilii (Holthuis, 1952) comb. nov. (was Paranchistus nobilii), and Polkamenes spondylis (Suzuki, 1971) comb. nov. (was Paranchistus spondylis). All sequences were accompanied by conspecific morphological data, assuming absence of intraspecific morphological variations in the chosen characters and specimens. To check the results of our combined dataset, an analysis only using morphological characters was performed, based on the methods used by Fransen (2002), de Gier and Fransen (2018), and de Gier et al. (2022), using paup v4.0a (Swofford, 2003) under the maximum parsimony (mp) criterion, with ordered characters and step matrices as mentioned above. A heuristic search was performed with 10.000 repetitions, with a number of trees that was automatically increased with 100. The strict consensus and the 50% majority rule consensus trees were obtained.

To reconstruct the evolution of host associations, an ancestral-character-state reconstruction was performed in R using the mp criterion and the ml tree from the te analysis as a backbone. The R-packages ape v. 5.5 (Paradis & Schliep, 2019), Geiger 2.0.7 (Penell et al., 2014) and phytools (Revell, 2012) were used. To get probability values for polytomous branches, the phytools function ‘rerootingMethod()’ was used, following Yang et al. (1995). The host-choice of Zenopontonia rex was changed from ‘Echinoderm and Mollusc (nudibranch/gastropod) associate’ to ‘Echinoderm associate’, due to technical limitations. Pie-charts displaying ml-values similar to the ones seen in comparable studies (e.g., Salis et al., 2018) were added in Abode Illustrator cc (Adobe Systems, USA). The actual ml-probabilities are presented in supplementary table S3 and supplementary fig. S4.

Phylogenetic trees were initially rooted and sorted in FigTree v1.4.4 (Rambaut, 2009), and consequently edited in Adobe Illustrator (cc).

Results

Molecular phylogeny reconstructions

The phylogenetic analysis using the concatenated alignment was resolved with moderately high support values (fig. 1). Most outgroup species were recovered as basal to the ingroup, with the tree being rooted with the two free-living species (Cuapetes tenuipes and Palaemonella rotumana). This is the case for three Cnidaria associates (two species of Actinimenes and Periclimenes kempi), and one Echinodermata associate (Lipkemenes lanipes). The other echinoderm-associated (and gastropod-associated) outgroups (two species of Zenopontonia Bruce, 1975, and Periclimenes colemani) were recovered in a large polytomy together with Paranchistus armatus (H. Milne Edwards, 1837) and a clade of all other ingroup species. Because of the polyphyly found in Paranchistus and Anchistus, a number of species from these genera were designated to three new genera, in both the molecular and combined (te) phylogeny reconstructions. The species are formally transferred to their new genera in the systematic account below.

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Phylogeny reconstruction based on the MrBayes tree topology of the concatenated molecular dataset (coi, 16S). RAxML bootstrap support and Bayesian posterior probabilities expressed as percentages are indicated respectively. Dashes (--) indicate values <50; asterisk (*) indicates different topology of RAxML or MrBayes tree. Barcodes are indicated by a collection accession number (rmnh.crus.d.) or a GenBank accession number. Species are listed in the appendices (supplementary table S1). Colours indicate various host associations. Zenopontonia rex (Kemp, 1922) is represented as a symbiont with two kinds of host associations: holothurians and nudibranchs.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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The ingroups consists of three main clades. The ascidian-associated genus Dasella, represented by Dasella herdmaniae (Lebour, 1938) in the molecular phylogeny reconstruction, is placed basal to the other (bivalve-associated) ingroup species (except for P. armatus), followed by a clade of Ensiger custoides (Bruce, 1977) comb. nov. and Ensiger custos (Forskål, 1775) comb. nov. Two species with now newly described genera, Polkamenes pycnodontae (Bruce, 1978) comb. nov. and Tympanicheles ornatus, are branching off respectively, after which an Anchistus clade consisting of three species is recovered. This clade is represented by one basal branch of A. australis, and one branch including Anchistus demani Kemp, 1922 and A. miersi. Anchistus demani is manifested as paraphyletic, with one species branching off earlier (rmnh.crus.d.48354). The placement of this specimen is discussed below.

Total Evidence approach

Four ingroup clades can be recognized in the phylogeny reconstruction resulting from the Total Evidence approach (fig. 2). The combined dataset using both morphology, as well as molecular data, recovered the outgroup in a similar way as the above mentioned topology (fig. 1). Zenopontonia rex and Periclimenes colemani were recovered as the outgroups being most related to the ingroup. This ingroup was recovered with low support values (51/--). The first clade containing the three species of Dasella was split off with high support values (98/75). Dasella ansoni and D. brucei, only represented by morphological data, were recovered as a sister clade of D. herdmaniae. The next clade branches off with somewhat low support values (86/--), containing three species: Paranchistus armatus, Ensiger custos, and E. custoides, of which the last two were recovered as most related to each other. The remaining ingroup species were recovered in two clades, one of which only includes species previously attributed to Paranchistus, but now to Polkamenes gen. nov.: P. liui (only represented by morphological data) branches off first in this clade, after which a polytomy of P. pycnodontae, P. nobilii, and P. spondylis was recovered. The latter two species were only represented by morphological data. The remaining ingroup species were recovered as a part of a large polytomy including three, now monophyletic genera: Tympanicheles gen. nov., Neoanchistus, and Anchistus. Tympanicheles pectinis (only represented by morphological data) is grouped together with T. ornatus with somewhat low support values (51/--), while the two species of Neoanchistus are recovered as closely related sister species (although both species are only represented by morphological data). A branch containing four species of Anchistus (A. miersi, A. demani, A. australis, and A. gravieri) is recovered with higher support values, with A. gravieri (being represented by morphological data) as the most basally placed species.

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Phylogeny reconstruction based on the MrBayes tree topology of the te approach. RAxML bootstrap support and Bayesian posterior probabilities expressed as percentages are indicated respectively. Dashes (--) indicate values <50; asterisk (*) indicates different topology of RAxML or MrBayes tree. Barcodes are indicated by a collection accession number (rmnh.crus.d.) or a GenBank accession number. Species are listed in the appendices (supplementary table S1). Species of which only morphological data was analysed are indicated with an asterisk (*) and no accession number. Colours indicate various host associations. Zenopontonia rex (Kemp, 1922) is represented as a symbiont with two main host associations: holothurians and nudibranchs.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Ancestral character state analysis

An ancestral character state reconstruction analysis resulted in Maximum Likelihood probabilities for all 24 internal nodes, which translate to the probabilities that an ancestral shrimp clade would have been associated to a certain host (fig. 3). One internal node was recovered as polytomous, but did not interfere with the resulting probabilities (see fig. 3). As expected, all internal nodes of the bivalve-associated clade containing all ingroup genera (except for Dasella) are fully resolved as associates of bivalve molluscs ( to 1.00). Similarly, the internal nodes in the clade containing the three species of Dasella are fully resolved as symbionts of ascidians.

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Phylogeny reconstruction based on the MrBayes tree topology of the te approach (fig. 2), with ancestral character state reconstructions on the internal nodes (probabilities are shown as pie charts). Colours indicate various host associations, both for the species as well as the ancestral character states. Zenopontonia rex (Kemp, 1922) is represented as a symbiont with two kinds of host associations (holothurians and nudibranchs), but was only classified as an echinoderm associate in the analysis. Species of which only morphological data was analysed are indicated with an asterisk next to the species names (*).

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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The common ancestor of the entire ingroup is recovered as a bivalve associate, but the probability for this character state barely reaches 51% () (fig. 3A). The chances of this common ancestor being an ascidian () or echinoderm associate () are much smaller. The common ancestor of a clade including the ingroup and the two most related outgroup species (Zenopontonia rex and Periclimenes colemani) is recovered as an echinoderm associate (). The ancestral character state of the clade described by Horká et al. (2016) (thus, also including the echinoderm associated Z. soror and Lipkemenes lanipes, and the cnidarian-associated species of Actinimenes and Periclimenes kempi) is recovered to most likely be cnidarian-associated () (fig. 3B).

Systematic account

Genera and species within the ‘Anchistus clade‘ are revised with remarks on their synonymy. Diagnoses, identification keys, geographical distributions, and host ranges are provided. Drawings of diagnostic characters and color photographs are added based on available material. Special attention is given to novel features of the ingroup species, mostly concerning mouthparts.

Abbreviations

Family Palaemonidae Rafinesque, 1815

Genus Anchistus Borradaile, 1898

Anchistus Borradaile, 1898: 387. Type species, by original designation: Harpilius Miersi De Man, 1888. Gender: masculine. Name placed on the Official List of Generic Names in Zoology in Opinion 470, in 1957.

Tridacnocaris Nobili, 1899: 234. Replacement name for Anchisus Borradaile, 1898. Type species therefore: Harpilius Miersi De Man, 1888. Gender: feminine. Name placed on the Official Index of Rejected and Invalid Generic Names in Zoology in Opinion 470, in 1957.

Diagnosis (emended from Bruce, 1995: 29). Small-sized shrimps of subcylindrical body form. Rostrum well developed, compressed, with teeth in distal part, lateral carinae feebly developed. Carapace smooth, glabrous; orbit feebly developed, inferior orbital angle distinct, antennal spine present or absent, supraorbital, hepatic and epigastric spines absent, anterolateral margin not produced. Abdomen smooth, glabrous, third segment not posterodorsally produced, anterior pleura rounded, posterior blunt. Telson with two pairs of small dorsal spines, three pairs of posterior spines. Eye small, cornea globular. Antennula normal, upper flagellum biramous, short ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed with large distolateral tooth. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp, laciniae broad; maxilla with simple palp, basal endite broad, bilobed, coxal endite obsolete, scaphognathite broad; first maxilliped with slender palp, basal endite broad, fused with coxal endite, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod bilobed; second maxilliped with normal endopod, dactylar segment small, exopod well developed, coxa feebly medially produced, epipod rounded, without podobranch; third maxilliped with endopod slender, ischiomerus and basis fused, exopod with numerous plumose setae distally, coxa with oval lateral plate, with rudimentary arthrobranch. Fourth thoracic sternite without median process. First pereiopods slender, chelae with fingers spatulate, non-cannulate, cutting edges minutely pectinate. Second pereiopods well developed, similar, unequal, dactylus with large acute triangular tooth in proximal half, fixed finger with series of teeth in proximal part; propodus with ventral oval tympanal organ proximally. Ambulatory pereiopods with simple or biunguiculate dactyli, without basal protuberance; unguis with dorsal pad of fine scale-like spinules. Uropod with protopodite posterolaterally acutely produced or rounded, exopod with small mobile distolateral spine, without distolateral tooth.

Four Anchistus species are recognized, all from bivalve hosts: Anchistus australis Bruce, 1977, Anchistus demani Kemp, 1922, Anchistus gravieri Kemp, 1922, and Anchistus miersi (De Man, 1888). Anchistus pectinis Kemp, 1925 is herein transferred to the new genus Tympanicheles.

Key to the species of Anchistus

1. 1.Carapace without antennal spine; protopodite of uropod rounded...……………2
2. –Carapace with antennal spine; protopodite of uropod acute ...……………..............3
3. 2.Rostrum with two dorso-distal teeth, ventrodistal margin rounded; fine scale-like spinules on unguis of ambulatory dactyli in transverse lines ..……A. demani
4. –Rostrum with 4-8 dorsal teeth in distal part of rostrum, ventral margin with one small subdistal tooth; fine scale-like spinules on unguis of ambulatory dactyli in longitudinal lines ...………...A. australis
5. 3.Ambulatory dactyli with corpus-unguis suture perpendicular to ventral margin; corpus without accessory tooth; lateral pair of posterior telson spines as small as dorsal spines, marginal ...…......A. gravieri
6. –Ambulatory dactyli with corpus-unguis suture strongly oblique; corpus with accessory tooth; lateral pair of posterior telson spines distinctly larger than dorsal spines, submarginal ...…….....A. miersi

Anchistus australis Bruce, 1977

(figs. 4A–B, 5, 39E–F)

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A) Anchistus australis Bruce, 1977, rmmh.crus.d.58048, stn ber.28, in Tridacna squamosa Lamarck, 1819; B) A. australis, rmnh.crus.d.53540, stn ter.12, in T. squamosa; C) Anchistus demani Kemp, 1922, rmnh.crus.d.42792, stn sey.792, in Tridacna maxima (Röding, 1798); D) A. demani, rmnh.crus.d.58049, stn thu.07, in T. maxima; E) Anchistus gravieri Kemp, 1922, rmnh.crus.d.58052, stn FR15, in Hippopus hippopus (L., 1758); F) Anchistus miersi (De Man, 1888), rmnh.crus.d.42970, stn sey.720, in T. squamosa: G) A. miersi, rmnh.crus.d.46473, sw Sulawesi, in T. squamosa; H) A. miersi, rmnh.crus.d.53568, stn ter.19, in T. squamosa.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

photographs by c.h.j.m. fransen

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Anchistus australis Bruce, 1977. A-H, L, M) rmnh.crus.d.41438; I–K) rmnh.crus.d.41436. A) habitus, lateral view, B) anterior appendages, lateral view; C) anterior appendages, dorsal view; D) rostrum, lateral, female, pocl. 7.0 mm; E) idem, male, pocl. 5.2 mm; F) idem, juvenile male, pocl. 1.1 mm; G) tail fan; H) telson; I) left major second pereiopod; J–K) idem, chela; L) dactylus left third pereiopod, medial view; M) idem, ventral view. Scale A, I = 4 mm; B, C, F, G = 2 mm; D, E, H, J, K, M = 1 mm; L = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Anchistus australis f. typica Bruce, 1977a: 56, figs. 7-9 [type locality: Capre Cay, Swain’s Reefs. Unavailable under Art. 15.2].

Anchistus australis f. dendricauda Bruce, 1977a: 62, figs. 10 [type locality: West Cay, Diamond Islets. Unavailable under Art. 15.2].

Anchistus australis Bruce, 1981b: 389, 395, fig. 3A; Bruce, 1983a: 43-44; Bruce, 1983b: 892, fig. 10A; Bruce, 1983c: 199 (listed); Bourdon, 1983: 867 (listed); Devaney & Bruce, 1987: 222; Bruce, 1990: 15, 18 (listed); Bruce, 1991a: 258-259, 275; Bruce, 1993: 55; Chace & Bruce, 1993: 71 (listed); Müller, 1993: 7 (listed); Strack, 1993: 53; Fransen, 1994a: 106, fig. 1; Bruce & Coombes, 1995: 106; De Grave, 1999: 126, fig. 1; Li, 2000: 6-7, fig. 6 (listed); Hayashi, 2002: 221, figs. 432a, b, 434a, b, 435a, b; Bruce, 2003b: 210 (listed); Hayashi, 2006: 510; Marin & Savinkin, 2007: table 2 (listed); De Grave & Fransen, 2011: 340 (listed); Fransen & Reijnen, 2012: 47; Hosie et al., 2015: 283 (listed); Liu, 2020: 312-313.

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Anchistus demani Kemp, 1922. A-G, I, J) rmnh.crus.d.41457; H) rmnh.crus.d.41480. A) habitus, lateral view, ovigerous female pocl. 3.8 mm; B) anterior appendages, lateral view, ovigerous female pocl. 3.8 mm; C) idem, dorsal view, ovigerous female pocl. 3.8 mm; D) rostrum, female pocl. 4.1 mm; E) idem, ovigerous female pocl. 3.8 mm; F) idem, male pocl. 2.6 mm; G) left second pereiopod; H, I) idem, chela; J) right third pereiopod dactylus, medial view. Scale A = 4 mm; B, C, G, = 2 mm; D-F, H, I, = 1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Material examined. INDONESIA: 1 male pocl. 5.2 mm (photo by M.S.S. Lavaleye 24/22-24), 1 female pocl. 7.00 mm (photo by M.S.S. Lavaleye 24/22-24) (rmnh.crus.d.41436), stn rbe.20, Ambon Island, Hitulama, 20.xi.1990, depth 15 m, scuba-diving, in Tridacna squamosa Lamarck, coll. C.H.J.M. Fransen and J. van Egmond. – 1 male pocl. 2.14 mm, 1 female pocl. 3.83 mm, 1 ovigerous female pocl. 2.92 mm (rmnh.crus.d.41437), stn rbe.16, W-side of Pombo Island, E of Ambon Island, 16.xi.1990, snorkeling, in T. squamosa, coll. J.C. den Hartog. – 1 male pocl. 2.99 mm, 20 juveniles pocl. 1.10-1.95 mm (rmnh.crus.d.41438), stn rbe.20, Ambon Island, Hitulama, 20.xi.1990, depth 15 m, scuba-diving, in large Tridacna sp. (Ø 39 cm), coll. C.H.J.M. Fransen & J. van Egmond. – 1 female pocl. 4.55 mm (rmnh.crus.d.41439), Nanaka, 7.ii.1980, in Tridacna sp., don. pppo. – 1 ovigerous female pocl. 7.5 mm (rmnh.crus.d.53540, GenBank JX185709; ct-scanned), stn ter.12, Ternate, Tanjung Tabam, 0°50’5.1”N 127°23’10”E, 30.x.2009, depth 8 m, scuba-diving, in T. squamosa, coll. C.H.J.M. Fransen, fcn. cf-00044, photo ter.12.0073-79. – 1 non ovigerous female pocl. 5.0 mm (rmnh.crus.d.58048), stn ber.28, ne Kalimantan, Berau Islands, Maratua Island, N-side, lagoon near entrance, 02°14’51.0“N 118°37’47.9”E, 17.x.2003, depth 8 m, scuba diving, in T. squamosa, coll. C.H.J.M. Fransen, film 16. – 1 ovigerous female pocl. 3.5 mm, 1 male pocl. 3.0 mm (rmnh.crus.d.27919), stn raj.28, W Papua, Raja Ampat Islands, N Batanta, N pulau Yarifi, 00°46.779’S 130°42.711’E, 28.xi.2007, depth 8 m, scuba diving, in T. squamosa, coll. C.H.J.M. Fransen, fcn. cf102. MALAYSIA: 1 ovigerous female pocl. 7.01 mm (rmnh.crus.d.41287), West Malaysia, Tioman Island, Telek Dalam, in T. squamosa; depth 10 feet, 22.vi.1983, coll. P. Ng. – 1 ovigerous female pocl. 5.3 mm, with bopyroid on left side under carapace (rmnh.crus.d.53859; GenBank JX185708), stn sem.18, Sabah, Semporna area, Ligitan Isl., 04°14’06.5”N 118°48’26.5”, 4.xii.2010, depth 5 m, scuba-diving, in T. squamosa, coll. dive guide Jerry.

Diagnosis. Rostrum with 4–7 dorsal distal and 0–1 ventral distal tooth, reaching just beyond the basal segment of the antennal peduncle. Sixth abdominal segment with posterior ventral angle rounded. Telson with small dorsal spines at 0.67 and 0.81 of telson length, with lateral pair of terminal spines small, situated next to intermediate spines. Antennal spine absent. Anterior margin between ventral orbital angle and antero-lateral angle almost straight. Basal segment of antennular peduncle with convex lateral margin and distolateral tooth. Deep slit present between distolateral spine and lamina of scaphocerite. Stylocerite acute. Chela of first pereiopod spatulate, non-cannulate, with cutting edges laterally minutely pectinate in distal 2/3rd, medially entire. Dactylus of chela of second pereiopod with one large triangular acute tooth in proximal half; fixed finger with 4–10 small teeth in proximal half. Palm with oval tympanal organ on medio-ventrally in proximal part. Dactylus of pereiopod 3–5 biunguiculate; flexor margin of corpus carinate with small triangular subdistal accessory tooth; unguis flattened with fine scale-like spinules in longitudinal lines. Protopod of uropod rounded.

Remarks. In one Tridacna squamosa specimen with a maximum width of 39 cm, one small male specimen (pocl. 2.99 mm) and 20 juveniles (rmnh.crus.d.41438) with carapace lengths between 1.10 and 1.95 mm were found. This indicates that part of one brood of a female remains in the host. Larval development may be somewhat abbreviated and planktonic larval stages remain in the host mantle cavity until molting in megalopa and subsequent juvenile stages. One can assume that the juveniles leave the host when they become adults. The smallest specimens show the rostrum more similar to certain Periclimenes O.G. Costa, 1844 species. The dorsal teeth are spread over the distal half of the rostrum and a rudiment of an epigastric spine is present in these youngsters. This implicates that the dorsal rostral spines ‘move’ forward after each moult, clustering together in the distal part in fully grown specimens.

The material corresponds well with the type description of A. australis f. typica. The characteristics of A. australis f. dendricauda, intermediate posterior terminal spines of telson terminating in series of short blunt processes, and dorsal rostral margin with eight teeth, were not encountered. The distolateral tooth of the basal segment of the antennular peduncle is more prominent than in the specimen figured by Bruce (1977a: fig. 7d and e).The number of teeth in the fixed finger of the second pereiopods usually is 10 in the adult specimens of the present material. In some, 7 teeth are present, and in the juveniles, sometimes even less than 7. Bruce (1977a) noted 4–5 teeth in the type-series.

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Anchistus demani Kemp, 1922, rmnh.crus.d.41457, female pocl. 4.1 mm. A) tailfan, dorsal view; B) distolateral part exopod uropod, dorsal view; C) telson, dorsal view; D) left mandible, ventral view; E) left maxillula, ventral view. Scale A = 1.25 mm; B, 0.125 mm; C = 0.25 mm; D, E = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Colour (figs. 4A–B). Large dark blue and/or red-brown dots on carapace, abdomen, pereiopods, scaphocerite, antennal peduncles and caudal fan.

Hosts. Recorded from Cardiidae, Tridacninae: Hippopus hippopus (L., 1758) (De Grave, 1999; Hayashi, 2006); Tridacna derasa (Röding) (Bruce, 1977a; Bruce, 1991a; Hayashi, 2002, 2006); Tridacna gigas (L., 1758) (De Grave, 1999; Hayashi, 2006); Tridacna maxima (Röding, 1798) (Hayashi, 2006); Tridacna squamosa Lamarck, 1819 (Bruce, 1977a, 1981b, 1983a, 1991a, 1993; Strack, 1993; De Grave, 1999; Hayashi, 2006; Fransen & Reijnen, 2012; Liu, 2020); Tridacna sp. (Bruce, 1983b; Bruce & Coombes, 1995; Hayashi, 2006).

Distribution. Queensland, Australia (Bruce, 1977a), Great Barrier Reef, Australia (Bruce, 1981b), Port Essington, Australia (Bruce, 1983a); Cobourg Peninsula, Australia (Bruce & Coombes, 1995); Fiji (Bruce, 1981b); Hainin Province, China (Liu, 2020); Seram Island, Indonesia (cf. Bruce, 1983b; Bourdon, 1983); Ambon Island, Indonesia (Strack, 1993; Fransen, 1994a); Ternate, Indonesia (Fransen & Reijnen, 2012); Sabah, Malaysia (Fransen & Reijnen, 2012); Tre Island, Vietnam (Bruce, 1993); Hansa Bay, Papua New Guinea (De Grave, 1999); New Caledonia (cf. Bruce, 1991a); Enewetak Atoll (Devaney & Bruce, 1987); Japan (Hayashi, 2002, 2006). Now for the first time recorded from Tioman island, West Malaysia, and from three new localities in Indonesia: Raja Ampat; NE Kalimantan; and Nanaka, Sulawesi.

Anchistus demani Kemp, 1922

(figs. 4C–D, 6–9)

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Anchistus demani Kemp, 1922, rmnh.crus.d.41457, female pocl. 4.1 mm. A) left maxilla, ventral view; B) left first maxilliped, ventral view. Scale = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus demani Kemp, 1922, rmnh.crus.d.41457, female pocl. 4.1 mm. A) left second maxilliped, ventral view; B) left third maxilliped, ventral view; C) left first pereiopod, lateral view. Scale A, B = 0.5 mm; C = 1.25 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus demani Kemp, 1922: 256, figs. 86–88 [Type locality: Aberdeen, Port Blair, Andamans, low tide]; Holthuis, 1952: 13 (listed); Holthuis, 1953: 56; Bruce, 1967: 568 (listed); Bruce, 1972a: 219 (listed); Hipeau-Jacquotte, 1972b: 9; Hipeau-Jacquotte, 1973a: 104, fig. 5; Bruce, 1974: 200–201; Bruce, 1975a: 150, 162 (listed); Bruce, 1975b: 26 (listed); Bruce, 1976b: 147 (listed); Bruce, 1976c: 22; Bruce, 1976d: 464; Bruce, 1977a: 50; Bruce, 1978a: 119; Bruce, 1978b: 287 (listed); Bruce, 1979a: 232; Bruce, 1981c: 3; Bruce, 1982: 276 (listed); Bruce, 1983b: 892; Bruce, 1983c: 200 (listed); Bruce, 1984: 147 (listed); Bruce, 1990: 15, 18 (listed); Bruce, 1991a: 259–260, 275, fig. 22; Bruce, 1993: 57; Müller, 1993: 8 (listed); Chace & Bruce, 1993: 72 (listed); Britayev & Fachrutdinov, 1994: 124, fig. 2A-C; Fransen, 1994a: 107, 110, 111, fig. 2d; Fransen, 1994b: 88, pl. 1C; Poupin, 1998: 12; De Grave, 1999: 132, text-fig. 4; Li, 2000: 9 fig. 9 (listed); Hayashi, 2002: 225; Bruce, 2003b: 211 (listed); Li et al., 2007: 177, fig. 74 (listed); Marin & Savinkin, 2007: table 2, 3 (listed); Bruce, 2010a: 63 (listed); De Grave & Fransen, 2011: 340 (listed); Radhakrishnan et al., 2012: table 1 (listed); Aznar-Cormano et al., 2015: 202 (listed); Samuel et al., 2016: table 1 (listed).

Anchistia cf. demani Rosewater, 1965: 381, 386.

Anchistus deseani – Strack, 1993: 46 [erroneous spelling].

Material examined. INDONESIA: 1 ovigerous female pocl. 3.81 mm (photo by M.S.S. Lavaleye 8/38a), 1 female pocl. 4.07 mm, 1 male pocl. 2.60 mm (rmnh.crus.d.41457), stn rbe.11, Ambon Island, Nusaniwe, 12.xi.1990, depth 2 m, snorkeling, found together in one Tridacna sp., coll. C.H.J.M. Fransen. – 1 female pocl. 2.21 mm (rmnh.crus.d.41458), stn rbe.16, Pombo Island E of Ambon Island, nw side, 16.xi.1990, snorkeling, in Tridacna squamosa Lamarck, coll. J.C. den Hartog. – 1 non ovigerous female () pocl. 2.5 mm (rmnh.crus.d.46481), sw Sulawesi, Spermonde Archipelago, Kudingareng Keke, S side, depth 3-5 m, snorkeling, 26.ix.1994, from Tridacna deresa (Röding) (Ø 20 cm), coll. J.C. den Hartog. – 1 female pocl. 2.7 mm with pair of abdominal bopyroids, rostrum damaged (rmnh.crus.d.46482), stn sul.04, N Sulawesi, Selat Lembeh, Pulau Lembey, Pantai Parigi, 01°28’N 125°14’E, small fringing reef, gently sloping from beach to 10 m, depth 1-3 m, snorkeling, 15.x.1994, in T. squamosa, coll. J.C. den Hartog. – 1 male 2.1 mm () (rmnh.crus.d.46483), stn sul.06, N Sulawesi, Selat Lembeh, Pulau Lembey, Pantai Parigi, 01°28’N 125°14’E, small fringing reef, gently sloping from beach to 10 m, depth 1-3 m, snorkeling, 15.x.1994, in T. squamosa, coll. J.C. den Hartog. – 1 ovigerous female pocl. 4.0 mm () (rmnh.crus.d.46484), stn sul.06, N Sulawesi, Selat Lembeh, Pulau Lembey, Pantai Parigi, 01°28’N 125°14’E, small fringing reef, gently sloping from beach to 10 m, depth 1–3 m, snorkeling, 15.x.1994, in Tridacna maxima (Röding) (Ø 20 cm), coll. J.C. den Hartog. – 1 male pocl. 1.9 mm (), 1 ovigerous female, pocl. 2.3 mm (), rmnh.crus.d.57965), stn ber.10, ne Kalimantan, Berau Islands, Samama Island, 02˚07’31.6”N 118˚20’09.7”E, 7.x.2003, depth 5 m, scuba diving, in Tridacna crocea Lamarck (Ø 10 cm), coll. C.H.J.M. Fransen, film 2/25-29. PHILIPPINES: 1 male pocl. 2.2 mm (), 1 female pocl. 4.0 mm () (rmnh.crus.d.48351), stn ceb.11, Cebu Strait, W of Bohol, E side of Cabilao Island, S of Cambacis, 9°52.92’N 123°47.37’E, patchy reef with algae, 14.xi.1999, depth 2-5 m, snorkeling, in T. maxima; coll. J.C. den Hartog. – 1 male pocl. 3.0 mm, 1 ovigerous female pocl. 4.9 mm (rmnh.crus.d.48354; GenBank OQ600396 (16S)), stn ceb.06, Cebu Strait, W of Bohol, N side of Cabilao Island, near Looc, 9°53.49’N 123°46.53’E, 9.xi.1999, depth 1 m, snorkeling, sandy reef flat with seagrass, in Hippopus hippopus (L.) (Ø 15 cm), coll. J.C. den Hartog. SEYCHELLES: 1 male pocl. 1.56 mm (rmnh.crus.d.42791), niop-E stn sey.754, St Joseph Atoll, nw rim, lagoon, 5°24’S 53°19’E, 26.xii.1992, depth 1 m, reef flat at low tide, snorkeling, in Tridacna sp. (Ø 18 cm); coll. J.C. den Hartog, photo 17/1517. – 1 ovigerous female pocl. 3.44 mm, 4 specimens pocl. 1.44, 2.25, 2.94, 3.06 mm (rmnh.crus.d.42792), niop-E stn sey.792, St François Atoll, W rim, 7°05’S 52°44’E, 5/6.i.1993, outer slope down to 27 m depth, scuba diving, in T.? maxima coll. C.H.J.M. Fransen, photo 33/512. RED SEA: 1 ovigerous female pocl. 3.38 mm (rmnh.crus.d.28583), Sudan, E of Port Sudan, Wingate reef, 5.ix.1970, on top of reef in shallow water, in Tridacna sp., coll. N.V.C. Polunin, no. 12. – 1 ovigerous female pocl. 4.16 mm (rmnh.crus.d.28584), Egypt, Gulf of Akaba, Sinai Peninsula, Marsa Murach, 22.viii.1967, coll. L. Fishelson, no. ns 2412. – 2 males pocl. 2.79 mm and 3.18 mm, 1 female pocl. 2.60 mm, 1 ovigerous female pocl. 4.81 mm (rmnh.crus.d.41480), SW of Umm Aabak, near Nocra Island, in Tridacna sp., 22.iii.1962, depth 0-2 m, Israel Red Sea Expedition no. E62/1378. – 1 male pocl. 3.12 mm (rmnh.crus.d.41481), Landing Bay, Entedibir Island, 31.iii.1962, in Tridacna sp., depth 2 m, Israel Red Sea Expedition no. E62/1432. – 1 male pocl. 2.79 mm (rmnh.crus.d.41482), Umm Aabak, 25.iii.1962, Israel Red Sea Expedition no. E62/2220. – 1 female pocl. 2.73 mm (rmnh.crus.d.41483), no further locality information; 1962, Israel Red Sea Expedition no. E62/1503. – 2 ovigerous females pocl. 2.0 and 2.5 mm, 1 male pocl. 1.5 mm, 1 juvenile pocl. 1.0 mm (rmnh.crus.d.58049), stn thu.07, Fsar, 22°13’46.4”N 39°01’44.5”E, 10.xi.2015, depth 12 m, in 3 small T. maxima, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 2.8 mm (rmnh.crus.d.58050), stn thu.14, Tahlah, 22°16’25.9”N 39°03’01.1”E, 13.xi.2015, depth 4 m, in small T. crocea, coll. C.H.J.M. Fransen. MICRONESIA: few specimens (rmnh.crus.d.28934), Palau Group, Ngemelis, S of Koror, -.iv.1971.

Diagnosis. Rostrum reaching distal end of basal segment of the antennular peduncle, distally typically bidentate (seldom only one tooth present). Antennal spine absent. Ventral orbital angle slightly produced. Antero-lateral angle of carapace rounded. Anterior margin of carapace between orbital ventral angle and antero-lateral margin straight. Sixth abdominal segment with posterior ventral angle rounded. Telson with dorsal spines minute, at 0.61 and 0.87 of telson length, with lateral pair of terminal spines small, situated subdistal to intermediate spines. Basal segment of antennular peduncle with distolateral angle rounded. Scaphocerite with straight lateral margin and deep slit between distolateral tooth and lamina. Third maxilliped with antepenultimate segment slightly broader than penultimate segment. First pereiopod with chela spatulate, non-cannulate; lateral cutting edges minutely pectinate in distal 2/3, medially entire. Second pereiopods with chela equal or unequal, dactylus with one large triangular tooth in proximal half; fixed finger with 4–11 small teeth in proximal half; palm with oval tympanal organ medio-ventrally in proximal half. Ambulatory pereiopods with dactylus biunguiculate; accessory tooth blunt and inconspicuous; dorsal flattened surface of unguis with fine scale-like spinules. Protopod of uropod rounded.

Remarks. Specimens correspond closely with previous descriptions. The first pereiopods have minutely pectinate cutting edges like the other members of the genus. The species seems close to A. australis in sharing the absence of an antennal spine, in having a deep slit between de distolateral tooth and the lamina of the scaphocerite, and in having similar ambulatory dactyli.

Colour (figs. 4C–D). The colour pattern is similar to that of A. miersi, e.g., transparent with numerous circular dark blue dots over body, antennae, chela of second pereiopods and caudal fan. Kemp (1922: 259) noted the dots to be pale green or red: “Two of the specimens, which were found together in a large Tridacna, were transparent when alive and dotted all over with pale green chromatophores. The female bore green eggs. The third specimen also found in Tridacna, was transparent with red chromatophores …”.

Hosts. Recorded from Cardiidae, Tridacninae: Tridacna? crocea Lamarck, 1819 (Bruce, 1979a); Tridacna gigas (L., 1758) (Holthuis, 1953); Tridacna maxima (Röding, 1798) (Bruce, 1974, 1976c, 1976d, 1977a, 1978a; 1993; Britayev & Fachrutdinov, 1994; Poupin, 1998); T.? maxima (Fransen, 1994b); Tridacna squamosa Lamarck, 1819 (Rosewater, 1961; Bruce, 1976d; Britayev & Fachrutdinov, 1994); Tridacna sp. (Holthuis, 1953; Bruce, 1981c; 1983b; 1991a; Fransen, 1994a). Newly reported from Hippopus hippopus (L., 1758); Tridacna derasa (Röding, 1798); and confirmed from T. crocea.

Distribution. Port Blair, Andaman Islands (Kemp, 1922); Marshall Islands (Holthuis, 1953; Rosewater, 1961); Gilbert Islands (Holthuis, 1953); Thailand (Rosewater, 1965); Perhantian Islands, Malaysia (Bruce, 1979a); Zanzibar and Kenya, East Africa (Bruce, 1976c, 1976d); Seychelles (Bruce, 1976c; Fransen, 1994b); Aldabra Island, Comoro Islands (Bruce, 1978a); Farquhar, Seychelles (Bruce, 1974); Capricorn group, Australia (Bruce, 1977a); Heron Island, Australia (Bruce, 1981c); Seram Island, Indonesia (Bruce, 1983b); Ambon, Indonesia (Fransen, 1994a); New Caledonia (cf. Bruce, 1991a); Tre Island, Vietnam (Bruce, 1993); South Vietnam (Britayev & Fachrutdinov, 1994); Tuamotu (Poupin, 1998). Here reported for the first time from East Kalimantan and Sulawesi, Indonesia; the Red Sea; Palau; and Cebu Strait, the Philippines.

Anchistus gravieri Kemp, 1922

(figs. 4B, 10–15)

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Anchistus gravieri Kemp, 1922, rmnh.crus.d.58051, Nathrang, ovigerous female, pocl. 6.9 mm. A) habitus, lateral; B) anterior appendages, dorsal view; C) idem, lateral view; D) telson, dorsal view; E) left second pereiopod; F) idem, chela; G) right third pereiopod dactylus. Scale A = 4 mm; B, C, E = 2 mm; D, F = 1 mm; G = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus gravieri Kemp, 1922, rmnh.crus.d.58052, Vanuatu (stn FR15). A–C, E) female, pocl. 4.2 mm; D, F, G) male, pocl. 3.9 mm. A) habitus, lateral view; B) anterior appendages, lateral view; C, D) idem, dorsal view; E, F) rostrum, lateral view; G) tail fan, dorsal view. Scale A = 4 mm; B-D = 2 mm; E-G = 1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus gravieri Kemp, 1922, rmnh.crus.d.58052, Vanuatu (stn FR15), female, pocl. 4.2 mm. A) left mandible, dorsal view; B) left maxillula, dorsal view; C) left maxilla, dorsal view; D) left first maxilliped, dorsal view. Scale = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus gravieri Kemp, 1922, rmnh.crus.d.58052, Vanuatu (stn FR15), female, pocl. 4.2 mm. A) left second maxilliped, dorsal view; B) left third maxilliped, dorsal view; C) left first pereiopod, lateral view; D) right second pereiopod, ventral view; E) idem, chela, medial view. Scale A, B = 0.5 mm; C = 1.25 mm; D = 2 mm; E = 1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus gravieri Kemp, 1922, rmnh.crus.d.58052, Vanuatu (stn FR15), female, pocl. 4.2 mm. A) right third pereiopod, lateral view; B) right fourth pereiopod, lateral view; C) left fifth pereiopod, medial view; D) right third pereiopod dactylus, medial view; E) idem, lateral view. Scale A-C = 1.25 mm; D, E = 0.125 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus gravieri Kemp, 1922, rmnh.crus.d.58052, Vanuatu (stn FR15), female, pocl. 4.2 mm. A) right fourth pereiopod dactylus, lateral view; B) left fifth pereiopod dactylus, medial view. Scale = 0.125 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus gravieri Kemp, 1922: 249 (key), 252-255, figs. 82–84 [Type locality: Vanikoro, Santa Cruz Islands, Polynesia]; Holthuis, 1952: 13 (listed); Bruce, 1967: 568; Bruce, 1972a: 219 (listed); Monod, 1972: 24, figs. 65-86; Hipeau-Jacquotte, 1972b: 9; Bruce, 1975a: 162; Bruce, 1977a: 47-50, figs. 2, 3; Bruce, 1983c: 200 (listed); Bruce, 1990: 15, 18 (listed); Bruce, 1991a: 260, 275, fig. 23; Müller, 1993: 9 (listed); Fransen, 1994a: 107, 111, fig. 2a; Li, 2000: 10, fig. 10 (listed); Hayashi, 2002: 225; De Grave & Fransen, 2011: 340 (listed).

not Anchistus gravieri – McNeill, 1953: 89 (= Polkamenes nobilii (Holthuis, 1952)).

Material examined. VIETNAM: 1 ovigerous female pocl. 6.9 mm (rmnh.crus.d.58051), Nathrang, entree 1948, st. 870 E. 413, in Tridacna sp., coll. R. Serène. VANUATU: 1 male pocl. 3.9 mm, 1 female pocl. 4.2 mm (rmnh.crus.d.58052), stn fr15, S Aoré Island, Bruat Channel, 15°21’56”S 167°5’44”E, 16.ix.2006, depth 3 m, hand picked, in Hippopus hippopus, coll. C.H.J.M. Fransen, fcn. cf57, photo T.-Y. Chan.

Diagnosis. Rostrum reaching end of penultimate segment of antennular peduncle, bent downward, with 2–4 dorsal distal teeth and one or none ventral tooth. Antennal spine well developed. Ventral orbital angle produced. Antero-lateral angle of carapace rounded. Anterior margin of carapace between ventral orbital angle and antero-lateral angle straight. Sixth abdominal segment with posterior ventral angle rounded. Telson with small dorsal spines at 0.61 and 0.79 of telson length, with lateral pair of terminal spines small, situated next to intermediate spines. Basal segment of antennular peduncle with or without distolateral tooth. Stylocerite acute. Scaphocerite with straight or slightly convex lateral margin, slit between distolateral tooth and lamina of moderate depth. First pereiopods with chela spatulate, not cannulate, with lateral cutting edges minutely pectinate in distal 2/3, medially entire. Second pereiopods unequal or equal, proximal half of palm with oval tympanal organ medio-ventrally in proximal part; dactylus with one, sometimes two, moderate triangular teeth in proximal half; fixed finger with 6–8 small teeth in proximal half. Ambulatory pereiopods with simple dactyli, not biunguiculate, dorsal flattened surface unguis with fine scale-like spinules. Protopod of uropod acutely produced.

Remarks. The specimens studied agree well with former descriptions of the species (Kemp, 1922; Monod, 1972; Bruce, 1977a, 1991a).

Colour (fig. 4E). Large dark blue dots on carapace, abdomen, pereiopods, scaphocerite, antennal peduncles and caudal fan.

Host. Recorded from Cardiidae, Tridacninae: Hippopus hippopus (L., 1758) (cf. Bruce, 1977a, 1991a); newly recorded from an unidentified Tridacna.

Distribution. Vanikoro Island, Santa Cruz Islands, Polynesia (Kemp, 1922); New Caledonia (Monod, 1972; Bruce, 1991a); Herald Island, Australia (Bruce, 1977a); Nathrang, Vietnam (Fransen, 1994a). Now recorded for the first time from Vanuatu.

Anchistus miersi (De Man, 1888)

(figs. 4F–G, 16, 39B,D)

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Anchistus miersi (De Man, 1888). A–D) rmnh.crus.d.41390, ovigerous female pocl. 3.9 mm; E–G) rmnh.crus.d.41389, ovigerous female pocl. 4.7 mm. A) habitus, lateral view; B) anterior appendages, dorsal view; C) idem, lateral view; D) telson, dorsal view; E) left second pereiopod, ventral view; F) idem, chela, medial view. Scale A = 4 mm; B, C, E = 2 mm; D, F = 1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Harpilius Miersi De Man, 1888: 274, pl. 17 figs. 6–10 [type locality: Elphinstone Island];? Whitelegge, 1897: 148.

Coralliocaris nudirostris – Nobili, 1899: 235.

non Anchistus Miersi – Nobili, 1906a: 48; Pérez, 1920: 1027 (both Polkamenes nobilii (Holthuis, 1952)).

Anchistus Miersi – Nobili, 1906b: 63; Nobili, 1907: 359; Holthuis, 1955: 62 (listed).

Marygrande mirabilis Pesta, 1911: 573, figs. 1–5 (partim) [type locality: Samoa]; De Grave, 2001: 129–134, figs. 4–5.

Anchistus miersi – Borradaile, 1898: 387; Borradaile, 1917: 324; Tattersall, 1921: 391; Seurat, 1934: 60; Kubo, 1940: 52–54, figs. 18-20 (pro parte); Holthuis, 1952: 110, 111 (full synonymy), fig. 45; Holthuis, 1953: 56; Johnson, 1961: 59, 62, 63, 76; Ooishi, 1964: 196 (listed); Johnson & Liang, 1966: 434; Miyake & Fujino, 1968: 414-415 (pro parte); Bruce, 1972a: 219, 222 photograph (listed); Miyake, 1972: 65, 210 (listed); Bruce, 1973: 136; Bruce, 1975b: 26 (listed); Fujino, 1975: 252-255, fig. 1, pl. 1; Monod, 1976b: 24, figs. 29-36; Bruce, 1976b: 147; Bruce, 1976c: 22; Bruce, 1976d: 464-465; Bruce, 1976e: 448; Watabe & Tomida, 1977: 46; Bruce, 1977b: 174-175; Bruce, 1978a: 119; Bruce, 1978b: 279; Bruce, 1979a: 232-233; Johnson, 1979: 31; Bruce, 1982: 267 (listed); Miyake, 1982: 32, pl. 11, fig. 6 (listed); Bruce, 1983c: 200 (listed); Bruce & Svoboda, 1983: 36 (listed); Bruce, 1984: 147 (listed); Vine, 1986: 101 (listed); Devaney & Bruce, 1987 (listed); Bruce, 1990: 15, 18 (listed); Holthuis, 1993: 130, fig. 111; Müller, 1993: 9 (listed); Bruce, 1993: 57, fig. 3A; Chace & Bruce, 1993: 72; Britayev & Fachrutdinov, 1994: 129, fig. 3E-F; Fransen, 1994a: 107, 110, 111, fig. 2c; Fransen, 1994b: 89, fig. 1D; Poupin, 1998: 12 (listed); De Grave, 1999: 132, pl. 1 figs. d, e; Li, 2000: 11, fig. 11 (listed); De Grave, 2001: 129-134, figs. 4–5; Hayashi, 2002: 223, figs. 432i, j, 434g, h, 435, g, h; Bruce, 2003b: 211 (listed); Li, 2004: 67; Hayashi, 2006: 510, 512; Marin & Savinkin, 2007: table 2 (listed); Li et al., 2007: 178, fig. 75 (listed); De Grave & Ashelby, 2011: table 1 (listed); De Grave & Fransen, 2011: 340 (listed); Radhakrishnan et al., 2012: table 1 (listed); Fransen & Reijnen, 2012; Hosie et al., 2015: 283 (listed); Neo et al., 2015: 877-878, figs. 1, 2; Anker & De Grave, 2016: 407; Samuel et al., 2016: table 1 (listed).

Anchistus meirsi – Fankboner, 1972: 35–41, figs. 1-3 [erroneous spelling].

Auchistus miersi – Strack, 1993: 46 [erroneous spelling].

Ancistus miersi – Ng et al., 1995: 43, fig. [erroneous spelling].

Material examined. INDONESIA: 2 ovigerous females pocl. 4.29, 4.74 mm (rmnh.crus.d.41389), stn rbe.30, Suli, 29.xi.1990, depth 1–3 m, snorkeling, in 2 Hippopus hippopus (L.) (Ø 15–20 cm), coll. H.L. Strack, one with pinnotherid. – 1 ovigerous female pocl. 3.90 mm (photo by M.S.S. Lavaleye 3/4-8) (rmnh.crus.d.41390), stn rbe.11, Nusaniwe, 12.xi.1990, snorkeling, depth 2 m, in Tridacna sp., coll. C.H.J.M. Fransen and J.C. den Hartog. – 1 male pocl. 3.25 mm, 1 female pocl. 4.87 mm (rmnh.crus.d.41391), Karimuajawa, Rotenoa, 25.iii.1974, don. pppo. – 1 male pocl. 3.90 mm, 1 female pocl. 4.94 mm (rmnh.crus.d.41392), Ambon Island, Ambon Bay, Tantoci, 3.vi.1975, coll. M.K. Moosa, Banner & Banner, Rumphius ii Expedition, don. pppo, fcn. cm 133. – 1 ovigerous female pocl. 7.47 mm (rmnh.crus.d.41393), Sunda Strait, Panaitan Island, 1983, don. pppo. – 1 male pocl. 5.00 mm, 4 females pocl. 4.74, 4.81, 6.04, 6.30 mm (rmnh.crus.d.41394), Java, Seribu Archipelago, Tikus Island, Goba, 24.x.1974, coll. S. Sidabutan, don. pppo. – 1 male pocl. 5.19 mm, 1 female pocl. 7.47 mm (rmnh.crus.d.41395), Java, Seribu Archipelago, Tikus Island, 26.v.1975, in Tridacna sp., don. pppo. – 1 male pocl. 5.84 mm, 2 females pocl. 5.84, 5.91 mm (rmnh.crus.d.41396), Java, Seribu Archipelago, Tikus Island, 27.v.1975, in Tridacna sp., coll. V. Toro, don. pppo. – 4 males pocl. 4.35, 4.74, 5.13, 5.39 mm, 3 females pocl. 2.47, 5.71 (with bopyrid under carapace), 7.34 mm (rmnh.crus.d.41397), Java, Seribu Archipelago, Tikus Island, 28.v.1975, in Tridacna sp., coll. V. Toro, don. pppo. – 1 male pocl. 5.3 mm (rmnh.crus.d.58053), Java, Seribu Archipelago, Tikus Island, 25.i.1975, coll. S. Sidabutan, don. pppo. – 2 females pocl. 4.48, 5.71 mm (rmnh.crus.d.41398), Ambon Island, Sowahtelu Archipelago, Morela, 03°32’00”S 128°12’30”E, 8.i.1973, coll. M.K. Moosa, don. pppo, fcn. cm 324. – 1 ovigerous female pocl. 7.79 mm (rmnh.crus.d.41399), E coast of Ajer Island, 21.iv.1971, 11.00 hr., R.V. “Mutiara ii”, don. pppo. – 1 male pocl. 4.87 mm, 1 ovigerous female pocl. 7.14 mm (rmnh.crus.d.41400), Sulawesi, Ujung Pandang, Kayangan Island, 7.vi.1975, coll. M.K. Moosa, Banner & Banner, Rumphius ii Expedition, don. pppo, fcn. cm 260. – 1 male pocl. 2.9 mm, 1 ovigerous female pocl. 3.8 mm (rmnh.crus.d.46472), SW Sulawesi, Spermonde Archipelago, Pulau Badi, nnw side, 3.x.1994, depth 0.5 m, snorkeling, in H. hippopus (Ø 20 cm), coll. J.C. den Hartog. – 1 male pocl. 3.2 mm, 1 ovigerous female pocl. 4.4 mm (rmnh.crus.d.46473), SW Sulawesi, Spermonde Archipelago, Barang Lompo, NW side, 23.ix.1994, depth 3–5 m, snorkeling, from Tridacna squamosa Lamarck, coll. J.C. den Hartog. – 1 male pocl. 2.1 mm, 1 ovigerous female pocl. 2.6 mm (rmnh.crus.d.46474), SW Sulawesi, Spermonde Archipelago, Gusung, harbour, NE side, 8.x.1994, depth 1–2 m, snorkeling, from T. squamosa (Ø 10 cm) in very turbid water, coll. J.C. den Hartog. – 1 ovigerous female pocl. 4.9 mm (rmnh.crus.d.46475), SW Sulawesi, Spermonde Archipelago, Kudingareng Keke, S side, 26.ix.1994, depth 3–5 m, snorkeling, in T. squamosa (Ø 15 cm), coll. J.C. den Hartog. – 1 male pocl. 3.4 mm, 1 ovigerous female pocl. 4.0 mm (rmnh.crus.d.46476), stn sul.06, N Sulawesi, Selat Lembeh, Pulau Lembey, Pantai Parigi, 01°28’N 125°14’E, 15.x.1994, small fringing reef, gently sloping from beach to 10 m, depth 1-3 m, snorkeling, in H. hippopus, coll. J.C. den Hartog. – 1 male pocl. 3.3 mm (rmnh.crus.d.46477), stn sul.08, N Sulawesi, Selat Lembeh, S of Tanjung Batuangus, channels between lava outflows, 01°30’N 125°15’E, 16.x.1994, fragile corals on slopes, down to muddy bottom, depth 1-3 m, snorkeling, in T. squamosa (Ø 25 cm), coll. I.J. Smit. – 1 ovigerous female pocl. 3.0 mm (rmnh.crus.d.46478), stn sul.13, N Sulawesi, Selat Lembeh, Air Bajo near Kareko, 01°29’N 125°15’E, 21.x.1994, sandy bay between rocks, N-exposed, gently sloping bottom, sandy beach to 4 m, large boulders, depth 0-5 m, snorkeling, in Tridacna maxima (Röding), coll. I.J. Smit. – 1 male pocl. 3.0 mm, 1 non-ovigerous female pocl. 2.5 mm (rmnh.crus.d.46479), stn sul.22, N Sulawesi, Selat Lembeh, Pulau Lembeh, near Batu Riri, 01°28’N 125°14’E, 31.x.1994, small enclosed bay, from sandy beach, seagrass belt, depth 2 m, scuba diving, in H. hippopus (Ø 20 cm), coll. C.H.J.M. Fransen. – 1 male pocl. 2.7 mm (rmnh.crus.d.46480), stn sul.22, N Sulawesi, Selat Lembeh, Pulau Lembeh, near Batu Riri, 01°28’N 125°14’E, 31.x.1994, small enclosed bay, from sandy beach, seagrass belt, depth 2 m, scuba diving, in H. hippopus (Ø 15 cm), coll. C.H.J.M. Fransen. – 1 male pocl. 3.7 mm, 1 female pocl. 6.1 mm (rmnh.crus.d.47688), stn mal.28, Moluccas, NW Seram, Kotania bay, SW of Pulau Marsegu, 03°01’S 128°03’E, 11.xi.1996, depth 20 m, scuba diving, in T. squamosa (Ø 40 cm) with Xanthasia sp. or Tridacnatheres sp., coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 1.9 mm (rmnh.crus.d.53568; GenBank JX185706), stn ter.19, Halmahera, Tidore, SW of Tobala, 0°44’56.6”N 127°23’13.5”E, 4.xi.2009, depth 10 m, scuba diving, sloping rubble reef, in small T.? squamosa, coll. C.H.J.M. Fransen, fcn. CF-00075, photo ter.19.0101-108. – 1 female pocl. 6.49 mm (zma.crus.D.204368), Siboga Expedition stn 78, Borneo Bank, Lumu-lumu Shoal, 3°24’S 117°36’E, 10/11.vi.1899, shore exploration, in Tridacna sp., depth 34 m, bottom coral and coral sand (publ. Holthuis, 1952: 110). – 1 male pocl. 2.66 mm, 1 ovigerous female pocl. 3.90 mm (rmnh.crus.d.41487), West Papua, Kameri, Noemfoor, 2.iii.1955, from local people, in Tridacna sp., leg. L.B. Holthuis no. 714. – 1 ovigerous female pocl. 6.4 mm (rmnh.crus.d.58030), stn ser.25, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Kotok Besar Island, NW-side, 5°41’56”S 106°32’23”E, 16.ix.2005, depth 5 m, scuba diving and snorkelling, in T. squamosa, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 3.8 mm (rmnh.crus.d.58032), stn ser.23, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, 15.ix.2005, depth 20 m, in Hyotissa hyotis (L.), coll. C.H.J.M. Fransen, film 9. – 1 ovigerous female, pocl. 3.6 mm (rmnh.crus.d.58054), stn ber.03, NE Kalimantan, Berau Islands, Derawan Island, S-side (jetty Derawan Dive Resort), 02°17’03.3”N 118°14’48.8”E, 13.x.2003, depth 0-2 m, snorkeling, in H. hippopus, coll. C.H.J.M. Fransen, film 10. MALAYSIA: few specimens (rmnh.crus.d.53798; GenBank JX185704); stn sem.40, Semporna, Ribbon Reef, 04°36’10.0”N 118°45’53.6”E, 11.xii.2010, depth 5 m, scuba diving,? in Tridacna sp., collected by boatman. – 1 non ovigerous female pocl. 2.0 mm (), 1 ovigerous female pocl. 3.2 mm (rmnh.crus.d.53806; GenBank JX185705), stn sem.22, Semporna, Bumbun Island W (channel), 04°27’40.7”N 118°38’09.1”E, 5.xii.2010, depth 3 m, scuba diving, in H. hippopus, coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 1.8 mm (rmnh.crus.d.53938; GenBank JX185707), stn sem.14, Semporna, Ligitan Isl., Ligitan 2, 04°09’35.8”N 118°52’22.2”E, 3.xii.2010, depth 5 m, in H. hippopus, coll. B.T. Reijnen. – 1 male pocl. 2.73 mm, 1 female pocl. 4.61 mm, 1 ovigerous female pocl. 4.03 mm (rmnh.crus.d.41387), West Malaysia, Tioman Island, Telok Dalam, 22.i.1983, in T. squamosa, depth 10 feet, coll. P.K.L. Ng. – 1 male, pocl. 4.55 mm; 1 female, pocl. 3.64 mm (rmnh.crus.d.41388); West Malaysia, Tioman Island, Tekek Bay, 23.vi.1983, depth 20 feet, in T. squamosa, coll. P.K.L. Ng. MALDIVES: 2 ovigerous females pocl. 7.79, 8.70 mm (rmnh.crus.d.15162), Addu Atol, Gan Island, 26.xii.1957, coll. S. Gerlach, Xarifa Expedition. RED SEA: 1 ovigerous female pocl. 6.10 mm (rmnh.crus.d.41486), Landing Bay, Entedibir Island, 3.iv.1962, Israel Red Sea Expedition no. E62/3842. – 1 ovigerous female pocl. 7.27 mm (rmnh.crus.d.41488), Dahab, 10.x.1968, in Tridacna sp., coll. L. Fishelson, NS 4401. – 1 ovigerous female pocl. 6.04 mm (rmnh.crus.d.41489), Landing Bay, Entedibir Island, 6.iv.1962, Israel Red Sea Expedition no. E62/2391. – 1 ovigerous female pocl. 6.62 mm (rmnh.crus.d.41490), Ras-A-Tanrar, 2.vii.1969, coll. L. Fishelson, NS 5826. SEYCHELLES: 1 ovigerous female pocl. 5.3 mm (rmnh.crus.d.42793), niop-E, stn sey.797, Platte Island atoll, 05°49’S 55°21’E, 7.i.1993, depth 12 m, lagoon of inner atoll, scuba diving, in T.? maxima, coll. C.H.J.M. Fransen. – 1 male pocl. 2.9 mm, 1 ovigerous female pocl. 4.0 mm (rmnh.crus.d.42790), niop-E stn sey.723, Bird Island, off N coast 3°42’S 55°12’E, 21xiiI.1992, depth 7 m, coral reef, near drop-off, scuba diving, in T. squamosa, coll. C.H.J.M. Fransen. PHILIPPINES: 1 male pocl. 2.99 mm (rmnh.crus.d.41386), Mactan Island near Cebu, Maribago, summer 1979, in Tridacna sp., coll. V. Storch. CAROLINE ISLANDS: 1 ovigerous female pocl. 3.38 mm (rmnh.crus.d.16511), Ifaluk, in front of Falarik, 26.ix.1953, depth 0.5–3 m, in H. hippopus, lagoon reef, coll. F.M. Bayer no. 402, don. usnm. MARSHALL ISLANDS: 1 ovigerous female pocl. 6.10 mm (rmnh.crus.d.16510), Eniwetok Atoll, N end of Island, 10.vii.1959, in Tridacna sp., coll. J.S. Garth, 59–3.

Diagnosis. Rostrum reaching just beyond basal segment of antennular peduncle, with 3–5 dorsal distal teeth, 0–2 ventral distal teeth. Antennal spine present. Ventral orbital angle slightly produced. Antero-lateral angle rounded. Anterior margin between ventral orbital angle and antero-lateral angle straight. Sixth abdominal segment with posterior ventral margin rounded. Telson with small dorsal pairs of spines at 0.63 and 0.79 of telson length, with lateral pair of terminal spines robust, placed just behind intermediate pair. Basal segment of antennular peduncle distally rounded, or with small distolateral tooth, not overreaching lamina. Scaphocerite with lateral margin straight, slit between distolateral tooth and lamina of moderate depth. Chela of first pereiopods spatulate, not cannulate, cutting edge laterally minutely pectinate in distal 2/3, medially entire. Dactylus of second chela with one large triangular tooth in proximal half, fixed finger with 5–10 small teeth in proximal half; palm with oval tympanal organ medio-ventrally in proximal part. Ambulatory dactyli biunguiculate; accessory tooth well developed, accessory tooth and flattened dorsal surface of unguis with fine scale-like spinules. Protopod of uropod acutely produced.

Remarks. The material corresponds closely to published descriptions. The distolateral tooth of the basal segment of the antennular peduncle is usually minute or absent. The position of the lateral pair of terminal spines of the telson just behind the intermediate pair is present in all investigated specimens.

The specimens investigated by Kubo (1940) appear not all belong to this species. The telson (fig. 20G) has the lateral terminal spines not in the characteristic position just behind the intermediate spines, but in the lateral position known of other Anchistus and Polkamenes. As Kubo (1940) had specimens from the bivalve Pteria sp., it is possible that his specimens belonged to Polkamenes pycnodontae.

The tympanal organ was first described and figured for this species by Monod (1976b: 24, fig. 33) as: “Le propode des chélipèdes porte d’un côté, et vers la base, une sorte d’aire déprimé ovalaire et cette fossette n’est pas un artefact puisqu’elle existe sur les deux appendices. Je n’ai rien trouvé à ce sujet dans la littérature mai ce détail a certainement dû se voir déjà remarqué”. This means that Monod had not encountered such a structure before and gave no suggestions for its function.

Colour (figs. 4F–H). Transparent with large blue or red-brown spots over body and appendages, ova green.

Hosts. Recorded from Cardiidae, Tridacninae: Hippopus hippopus (L., 1758) (Holthuis, 1953; Miyake & Fujino, 1968, Fankboner, 1972; Bruce, 1977b; Fransen, 1994a; Hayashi, 2002, 2006; Fransen & Reijnen, 2012); Tridacna crocea Lamarck, 1819 (Miyake & Fujino, 1968; Hayashi, 2002, 2006); Tridacna gigas (L., 1758) (Fankboner, 1972; Bruce, 1983b; Hayashi, 2006); Tridacna elongata Lamark, 1819 (= Tridacna maxima (Röding, 1798))(Ooishi, 1964; De Grave, 1999); T. maxima (Kubo, 1940; Bruce, 1976d, 1978a, 1993; Britayev & Fachrutdinov, 1994; Hayashi, 2002, 2006); T.? maxima (Fransen, 1994b); Tridacna squamosa Lamarck, 1819 (many records; Borradaile, 1917; Kubo, 1940; Miyake & Fujino, 1968; Bruce, 1976b, 1976c, 1976d, 1979a, 1993; Britayev & Fachrutdinov, 1994; Fransen, 1994b; Ng et al., 1995; Hayashi, 2002, 2006; Neo et al., 2015); Tridacna? squamosa (Fransen & Reijnen, 2012); Tridacna sp. (Holthuis, 1952; Johnson, 1961; Bruce, 1973, 1976e, 1978b, 1979a, 1993; Fujino, 1975; De Grave, 1999; Fransen & Reijnen, 2012); Tridacna sp. (Li, 2004). Also recorded from Margaritidae: Pinctada maxima (Jameson, 1901) (Kubo, 1940; Miyake & Fujino, 1968; Hayashi, 2002, 2006); Pinctada margaritifera (L., 1758) (Seurat, 1934; Hayashi, 2006); Pinctada fucata (A. Gould, 1850) (Hayashi, 2006, as Pinctada martensii (Dunker, 1880)). From Pinnidae: Pinna sp. (Nobili, 1906b; Tattersall, 1921; Hayashi, 2002, 2006); Streptopinna saccata (L., 1758) (Hayashi, 2006). From Pteriidae: Pteria penguin (Röding, 1798) (Kubo, 1940, as Pteria macroptera (Lamarck, 1819); De Grave, 1999, as Magnavicula penguin/ Magnavicula bennetti Iredale, 1939); Pteria sp. (Nobili, 1907 (with doubt); Hayashi, 2002, 2006).

Distribution. Widely distributed in the Indo-Pacific, from the Red Sea to Moçambique and Madagascar to the Gambier Archipelago in the east. Kenya, Tanganyika and Zanzibar, East Africa (Bruce, 1976c, 1976d); Red Sea (Nobili, 1899, 1906b; Tattersall, 1921; Vine, 1986); Persian Gulf (Nobili, 1906a); Comoro Islands (Bruce, 1978a); Seychelles (Borradaile, 1917; Bruce, 1976b); Egmont, Chagos Islands (Borradaile, 1917, see also Bruce, 1976b); Maldives (Borradaile, 1917; Bruce, 1976e, 1993); Madagascar (Bruce, 1978b); Perhentian Islands, Malaysia (Bruce, 1979a); Sabah, Malaysia (Fransen & Reijnen, 2012); Penang, Malaysia (Johnson, 1979); Lumulumu Shoal, Borneo Bank, Indonesia (Holthuis, 1952); Anambas, Indonesia (Li, 2004); Ambon, Indonesia (Holthuis, 1993; Fransen, 1994a); Tidore, Indonesia (Fransen & Reijnen, 2012); Singapore (Johnson, 1961, 1979; Anker & De Grave, 2016; Neo et al., 2015); Tre Island, Vietnam (Bruce, 1993); Philippines (Chace & Bruce, 1993); Mergui Archipelago (De Man, 1888); British New Guinea (= Southern Papua New Guinea) (Borradaile, 1898); Queensland, Australia (Bruce, 1977b); Papua New Guinea (De Grave, 1999); Nouméa, New Caledonia (Monod, 1976b); Japan (Hayashi, 2002, 2006); Ryukyu Islands, Japan (Fujino, 1975); Marshall Islands (Holthuis, 1953); Palau (Kubo, 1940); French Polynesia (Nobili, 1907); Gambier Islands (Seurat, 1934); Funafuti Atoll (Whitelegge, 1897). Now for the first time recorded from the Caroline Islands, Micronesia; and from the following locations in Indonesia: Panaitan Island, Seribu, and the Thousand Islands, Sunda strait; NE and S Kalimantan; Numfor, West Papua; SW and N Sulawesi; and NW Seram, the Mollucas.

Genus Dasella Lebour, 1945

Dasia Lebour, 1938: 650. Type species, by monotypy: Dasia herdmaniae Lebour, 1938. Gender: feminine. Invalid junior homonym of Dasia Gray, 1839 (Reptilia), and Dasia van der Goot, 1918 [in B. Das, 1918] (Hemiptera).

Dasella Lebour, 1945: 279. Replacement name for Dasia Lebour, 1938. Type species therefore Dasia herdmaniae Lebour, 1938.

Diagnosis (emended from Bruce, 1995: 47). Small sized shrimps of subcylindrical body form. Rostrum well developed, compressed, dorsal margin without teeth, ventral margin with or without minute distal tooth, lateral carinae feebly developed. Carapace smooth, glabrous; inferior orbital angle produced, orbit feebly developed, antennal spine present, hepatic spine mobile, supraorbital and epigastric spines absent, anterolateral margin rounded, not produced. Abdomen smooth, glabrous, third segment not posterodorsally produced, pleura broadly rounded. Telson with two pairs of large dorsal spines, three pairs of posterior spines. Eye small, cornea globular. Antennula with basal segment of peduncle with distolateral tooth, flagella short, short free ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed with small distolateral tooth. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp, laciniae moderately broad; maxilla with simple palp, basal endite broad, bilobed, coxal endite obsolete, scaphognathite broad; first maxilliped with slender palp, basal endite broad, fused with coxal endite, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod rectangular or rounded, without podobranch; third maxilliped with endopod slender, ischiomerus and basis fused, exopod with numerous plumose setae distally, coxa not medially produced, with large lateral plate, without arthrobranch. Fourth thoracic sternite without median process. First pereiopods moderately robust, chelae with fingers subspatulate, non-cannulate, cutting edges minutely pectinate. Second pereiopods well developed, similar, unequal, fingers simple, unarmed; palm without tympanal organ. Ambulatory pereiopods with dactyli strongly compressed, unguis distinct with scattered scale-like spinules, corpus with armed or unarmed distoventral process. Uropod with protopodite acutely produced, exopod of uropod with small distolateral tooth with larger mobile spine medially.

Three species are designated to this genus: Dasella ansoni Bruce, 1983, Dasella brucei Berggren, 1990, and Dasella herdmaniae (Lebour, 1938).

Key to the species of Dasella

1. 1.Propodal spines on pereiopod 3–5 long, sharp; minute ventral tooth on rostrum (sometimes absent); length of rostrum barely about as long as the antennular peduncle........................................................2
2. –Propodal spines on pereiopod 3–5 long, club-shaped; no teeth on rostrum; length of rostrum much shorter than antennular peduncle.........................D. herdmaniae
3. 2.Large blunt tooth on dactylus of pereiopod 3–4 with hooked process....D. ansoni
4. –Large blunt tooth on dactylus of pereiopod 3–4 without hooked process...........................................................................D. brucei

Dasella ansoni Bruce, 1983

Dasella ansoni Bruce, 1983d: 22, figs. 1–5 [Type locality: Arafura Sea, 10°58’S 132°10’E, 27 m; see Bruce & Coombes, 1995]; Berggren, 1990: 558 (listed); Bruce, 1990: 10, 16, 18 (listed); Müller, 1993: 23 (listed); Holthuis, 1993: 140, fig. 123 (listed); Bruce & Coombes, 1995: 108 (listed); Li, 2000: 41, fig. 41 (listed); De Grave & Fransen, 2011: 348 (listed).

Diagnosis (based on Bruce, 1983d). Small-sized shrimp. Rostrum barely reaching distal border of distal segment of antennular peduncle, slightly depressed, acute, dorsally thickened, without distinct lateral carinae, without dorsal teeth, with one acute minute ventral tooth near tip. Antennal spine present, small. Hepatic spine well-developed, small, mobile, below level of than antennal spine. Inferior orbital angle distinct, produced. Antero-lateral angle of carapace broadly rounded, feebly produced. Anterior margin of carapace between ventral orbital angle and antero-lateral angle straight. Sixth abdominal segment with posterolateral angle acute, posteroventral angle feebly acute. Telson with large dorsal spines at 0.35 and 0.50 of telson length, lateral pair of terminal spines just behind intermediate pair, distal margin of telson rounded, without median process. Basal segment of antennular peduncle with one small distolateral tooth. Scaphocerite with lateral margin almost straight, slit between small distolateral tooth and lamina shallow. Chela of first pereiopods spatulate, with cutting edges minutely pectinate along entire rim. Second pereiopods unequal; almost straight dactylus barely exceeding fixed finger on both chelae, without teeth on cutting edges; palm without tympanal organ. Ambulatory dactyli with large broad distoventral process on flexor margin of corpus, accompanied by small hooked tooth on tip in third and fourth pereiopods; unguis simple, acute. Distoventral spines on ambulatory propodi long, acute.

Colour. Generally transparent; rostrum, antennular peduncles and chelae of second pereiopods feebly spotted with small white dots (Bruce, 1983d).

Hosts. Only known to be associated with one species of ascidian: Phallusia depressiuscula (Heller, 1878) (Ascidiidae) (Bruce, 1983d).

Distribution. Only known from its type locality: Arafura Sea (10°58’S 132°10’E), Australia (Bruce, 1983d; Bruce & Coombes, 1995).

Dasella brucei Berggren, 1990

Dasella herdmaniae Bruce, 1981a: 50-56, figs. 1–2. (not Dasella herdmaniae (Lebour, 1938)).

Dasella brucei Berggren, 1990: 558 [Type locality: Heron Island, Queensland, Australia, 15 m]; Bruce, 1990: 10, 16, 18 (listed); Müller, 1993: 23 (listed); Li, 2000: 42, fig. 42 (listed); Bruce, 2003a: 111, fig. 1; De Grave & Fransen, 2011: 348 (listed).

Diagnosis (based on Bruce, 1981a). Small-sized shrimp. Rostrum exceeding proximal segment of antennular peduncle, slightly depressed, acute, dorsally thickened, without distinct lateral carinae, without dorsal teeth, without or with one acute minute ventral tooth near tip. Antennal spine present, small. Hepatic spine well-developed, small, mobile, below level of antennal spine. Inferior orbital angle distinct, produced. Antero-lateral angle of carapace broadly rounded, feebly to strongly produced. Anterior margin of carapace between ventral orbital angle and antero-lateral angle somewhat straight. Sixth abdominal segment with posterolateral angle acute, posteroventral angle feebly acute. Telson with large dorsal spines at 0.40 and 0.70 of telson length, lateral pair of terminal spines just behind intermediate pair, distal margin of telson with median acute process. Basal segment of antennular peduncle with one small distolateral tooth. Scaphocerite with lateral margin almost straight, slit between small distolateral tooth and lamina shallow. Chela of first pereiopods spatulate, with cutting edges minutely pectinate along entire rim. Second pereiopods unequal, with dactylus barely exceeding fixed finger on both chelae, without teeth on cutting edges; palm without tympanal organ. Ambulatory dactyli biunguiculate, with large broad distoventral process on flexor margin of corpus; unguis simple, acute. Distoventral spines on ambulatory propodi long, acute.

Colour. Unknown.

Hosts. Known from two species of ascidians: Herdmania grandis (Heller, 1878) (Bruce, 2003a) and Herdmania momus (Savigny, 1816) (Pyuridae) (Bruce, 1981a, 2003a).

Distribution. Three localities off Queensland, Australia: Heron Island, Murdock Point (Mooloolaba), and Moreton Bay (Berggren, 1990; Bruce, 2003a).

Dasella herdmaniae (Lebour, 1938)

(figs. 17–19)

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Dasella herdmaniae (Lebour, 1938) from Herdmania momus (Savigny, 1816). A) rmnh.crus.d.53924, stn sem.52; B) rmnh.crus.d.53535, stn ter.10.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

photographs by c.h.j.m. fransen

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Dasella herdmaniae (Lebour, 1938). A) rmnh.crus.d.57964, ovigerous female, pocl. 3.8 mm; B–E) rmnh.crus.d.48249, 1 ovigerous female pocl. 3.4 mm. A) habitus, lateral view; B) left mandible, ventral view; C) left maxillula, ventral view; D) left maxilla, ventral view; E) left first maxilliped, ventral view. Scale A = 2 mm; B–E = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by w. de gier (a) and c.h.j.m. fransen (b–e)

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Dasella herdmaniae (Lebour, 1938). rmnh.crus.d.48249, 1 ovigerous female pocl. 3.4 mm. A) left second maxilliped, ventral view; B) left third maxilliped, ventral view; C) left first pereiopod, lateral view; D) right fifth pereiopod dactylus, medail view. Scale A, B = 0.5 mm; C = 1.25 mm; D = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Dasia herdmaniae Lebour, 1938: 650, plate 1 [type locality: Tuticorin, Gulf of Manaar, Madras, India, associated with ascidian Herdmania pallida (Heller, 1878) (= Herdmania momus (Savigny, 1816))].

Dasella herdmaniae – Lebour, 1945: 279; Holthuis, 1952: 17 (listed); Holthuis, 1955: 68, fig. 4lc, d (listed); Bruce, 1976a: 89; Bruce, 1981a: 50, figs. 1, 2; Bruce, 1981c: 5; Bruce, 1983c: 201 (listed); Berggren, 1990: 554, figs. 1–3; Chace & Bruce, 1993: 78–79; Müller, 1993: 23 (listed); Li, 2000: 42, fig. 43 (listed); Bruce, 2010a: 63 (listed); De Grave & Fransen, 2011: 348 (listed); Radhakrishnan et al., 2012: table 1 (listed); Horká et al., 2016: 6, figs. 2-4; Samuel et al., 2016: table 1 (listed); Chow et al., 2021: table A.1.

Material examined. INDONESIA: 1 male pocl. 2.6 mm, 1 ovigerous female pocl. 3.8 mm (rmnh.crus.d.49846; GenBank KU170689), stn bal.14, Bali, NE-side Pulau Serangan, off lighthouse, 08°43’17”S 115°15’31”E, 5.iv.2001, 16 m depth, scuba diving, slowly declining reef slope, sandy base, in Herdmania momus (Savigny), translucent, coll. C.H.J.M. Fransen. – 1 male, pocl. 2.5 mm, 1 ovigerous female pocl. 2.5 mm, (rmnh.crus.d.58055), stn bal.05, Sanur, Penjor Point, 08°41’36”S 115°16’20”E, 1.iv.2001, depth 15 m, scuba diving, slowly declining reef slope, sandy base, in H. momus, translucent with red chromatophores of body and appendages, coll. C.H.J.M. Fransen, photo C.H.J.M. Fransen & W. Renema. – 1 male pocl. 2.2 mm, 1 non-ovigerous female pocl. 2.2 mm, (rmnh.crus.d.58056), stn bal.05, Sanur, Penjor Point, 08°41’36”S 115°16’20”E, 1.iv.2001, depth 15 m, scuba diving, slowly declining reef slope, sandy base, in H. momus, translucent with red chromatophores over body and appendages, coll. C.H.J.M. Fransen. – 1 male pocl. 2.7 mm, 1 non-ovigerous female pocl. 1.9, 2.8, 3.5, 3.6 (with bopyroid) mm, (rmnh.crus.d.58057), stn bal.13, NE-side Pulau Serangan, Loloan Serangan, 08°43’39”S 115°15’13”E, 5.iv.2001, depth 15 m, scuba diving, slowly declining reef slope, sandy base, in H. momus, translucent with red chromatophores over body and appendages, coll. C.H.J.M. Fransen. – 1 specimen pocl. 1.1 mm (rmnh.crus.d.58058), stn bal.12, E-side Nusa Dua, off Club Med Hotel, N of channel, 08°47’06”S 115°13’57”E, 4.iv.2001, depth 18 m, slowly declining reef slope, sandy base, in ascidian, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 4.3 mm (rmnh.crus.d.48254), stn sul.18, N Sulawesi, Selat Lembeh, near Tandarusa, Sarena Kecil West, 01°27’N 125°13’E, 24.x.1994, depth 2 m, snorkeling, sandy bank, from sandy shore to coral covered slope, in tunicate, coll. J.C. den Hartog. – 1 non ovigerous female pocl. 1.8 mm (rmnh.crus.d.48253), SW Sulawesi, Spermonde Archipelago, Barang Lompo, NW side, 23.ix.1994, depth 3–5 m, scuba diving, in Polycarpa sp. ascidian, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 3.0 mm, 1 male pocl. 2.1 mm (rmnh.crus.d.48252), SW Sulawesi, Spermonde Archipelago, Kudingareng Keke, ssw side, 28.ix.1994, depth 3–5 m, scuba diving, in ascidians, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 4.6 mm, 1 male pocl. 3.1 mm, 1 non ovigerous female pocl. 3.5 mm, 1 juvenile pocl. 1.6 mm (rmnh.crus.d.48251), SW Sulawesi, Spermonde Archipelago, Pulau Badi, nnw side, 3.x.1994, depth 15 m, scuba diving, in large solitary milkey white transparent ascidians, coll. C. Massin. – 1 ovigerous female pocl. 4.1 mm (rmnh.crus.d.48250), stn sul.08, N Sulawesi, Selat Lembeh, S of Tanjung Batuangus, channels between lava outflows, 01°30’N 125°15’E, 25.x.1994, depth 2–5 m, snorkeling, fragile corals on slopes, down to muddy bottom, coll. J.C. den Hartog. – 1 ovigerous female pocl. 3.4 mm (rmnh.crus.d.48249), stn rbe.38, Moluccas, Ambon, Hitu, E coast, N of Tengah tengah, 8.xii.1990, depth 10 m, scuba diving, in ascidian, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 2.5 mm (rmnh.crus.d.48248), stn rbe.34, Moluccas, Ambon, Hitu, Ambon Bay, outer bay, Rumahtiga, 5.xii.1990, depth 3–5 m, scuba diving,? from ascidian, coll. C.H.J.M. Fransen, photo M.S.S. Lavaleye. – 1 male pocl. 2.9 mm (rmnh.crus.d.47589), stn mal.24, Moluccas, Ambon, S coast, Seri bay, 03°45’S 128°09’E, 22.xi.1996, depth 15 m, scuba diving, in solitary ascidian, H. momus, coll. C.H.J.M. Fransen. – 1 male pocl. 2.6 mm, 1 ovigerous female pocl. 4.7 mm (rmnh.crus.d.47582), stn mal.20, Moluccas, Ambon, Ambon bay, N coast W of Lilibooi, 03°45’S 128°01’E, 20.xi.1996, depth 30 m, scuba diving, from large solitary ascidian aff. Phallusia Savigny, coll. C.H.J.M. Fransen. – 1 male pocl. 2.8 mm, 1 female pocl. 4.2 mm (rmnh.crus.d.47580), stn mal.24, Moluccas, Ambon, S coast, Seri bay, 03°45’S 128°09’E, 22.xi.1996, depth 15 m, scuba diving, in H. momus, coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 2.0 mm, 1 male pocl. 2.5 mm (rmnh.crus.d.47579), stn mal.32, Moluccas, Ambon, E coast, close to Cape Meriam, 03°38’S 128°21’E, 23.xi.1996, depth 10 m, scuba diving, in solitary ascidian aff. Phallusia, coll. C.H.J.M. Fransen. – 1 male pocl. 2.5 mm with pair of abdominal bopyroids, 1 non ovigerous female pocl. 1.8 mm (rmnh.crus.d.47577), stn mal.24, Moluccas, Ambon, S coast, Seri bay, 03°45’S 128°09’E, 22.xi.1996, depth 15 m, scuba diving, in H. momus, leg. C.H.J.M. Fransen. – 1 ovigerous female pocl. 2.4 mm (rmnh.crus.d.53535; GenBank OQ603086 (coi)), stn ter.10, Halmahera, Maitara, Maitara NW, 0°44’32”N 127°21’50.9”E, 29.x.2009, depth 7 m, scuba diving, coral reef with sandy patches, corals and sea fans abundant, in H. cf. momus (Asc. 33), coll. C.H.J.M. Fransen, fcn. cf-00039, photo ter.10.0171-175. – 1 ovigerous female pocl. 3.0 mm, 1 male pocl. 2.6 mm (rmnh.crus.d.58059), stn ter.21, Tanjung Ratemu (S of river), Halmahera mainland, 0°54’24.7”N 127°29’17.7”E, 5.xi.2009, depth 8 m, in ascidian (Asc 91), coll. A. Gittenberger. – 3 males pocl. 1.6, 1.7 and 2.0 mm, 1 non ovigerous female pocl. 1.4 mm (rmnh.crus.d.57964; GenBank OQ603089 (coi) & OQ600397 (16S)), stn. lem.03, NE Sulawesi, Lembeh Strait, E Sarena Besar, 1°27’34.1634”N 125°14’1.896”E, 31.i.2012, depth 15 m, in H. momus, coll. C.H.J.M. Fransen. – 2 ovigerous females pocl. 3.3 mm, 1 male pocl. 2.8 mm, with abdominal bopyroid), 1 non ovigerous female pocl. 2.8 mm (rmnh.crus.d.58060), stn lem.21, NE Sulawesi, Lembeh Strait, Tanjung Kungkungan, 1°27’58.392”E 125°14’2.2554”E, 10.ii.2012, depth 4 m, in H. momus, coll. C.H.J.M. Fransen. – 3 males pocl. 2.7 mm and 2.4 and 2.5 mm, 1 ovigerous females pocl. 4.1 mm (rmnh.crus.d.58061), stn lem.33, NE Sulawesi, Lembeh Strait, Tanjung Nanas I, 1°27’39.492”N 125°13’35.7954”E, 17.ii.2012, depth 15 m, each pair in H. momus, coll. C.H.J.M. Fransen. – few specimens (rmnh.crus.d.58062), stn ser.16, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Sepa Island, NW-side, 5°34’32”S 106°34’48”E, 13.ix.2005, unknown depth, scuba diving, in ascidian, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 4.4 mm (rmnh.crus.d.54134), stn raj.19, W Papua, Raja Ampat Islands, Maya’s mimpi, 00°30.456’S 130°39.919’E, 25.xi.2007, depth 20 m, scuba diving, in H. momus, coll. J.D. Thomas. – 1 ovigerous female pocl. 4.0 mm (rmnh.crus.d.58063), stn raj.26, W Papua, Raja Ampat Islands, S. Gam, E entrance Besir Bay, Bun Isl., 00°30.988’S 130°33.812’E, 27.xi.2007, depth 2–12 m, in ascidian? Polycarpa sp., coll. J.D. Thomas. MALAYSIA: 1 ovigerous female pocl. 3.3 mm (rmnh.crus.d.53860), stn sem.37, Sabah, Semporna area, S Boheydulang Isl., outer reef, 04°35’00.3”N 118°46’39.1”E, 11.xii.2010, depth 7 m, scuba diving, in H. momus, coll. C.H.J.M. Fransen. – 1 male pocl. 2.3 mm (rmnh.crus.d.53870; GenBank OQ603087 (coi)), stn sem.31, Sabah, Semporna area, N Kulapuan Isl., 04°32’09.6”N 118°50’18.6”E, 9.xii.2010, depth 20 m, scuba diving, in H. momus, coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 4.4 mm, 1 ovigerous female pocl. 2.9 mm, 1 male pocl. 2.6 mm (rmnh.crus.d.53967; GenBank OQ603088 (coi)), stn sem.57, Sabah, Semporna area, S Larapan Isl. 2, 04°32’51.1”N 118°36’31.3”E, 17.xii.2020, depth 12 m, scuba diving, in H. momus, coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 2.4 mm (rmnh.crus.d.53924; GenBank KU064966), stn sem.52, Sabah, Semporna area, Silumpat Isl., 04°45’58.7”N 118°23’25.6”E, 16.xii.2010, depth 25 m, scuba diving, in H. momus, coll. C.H.J.M. Fransen, photo 1263–1270. MOZAMBIQUE: 1 male pocl. 1.4 mm, 1 ovigerous female pocl. 2.3 mm (rmnh.crus.d.39850), Inhaca Island, 26°S 33°W, 19.i.1990, depth 5 m, scuba diving, associated with Pyura stolonifera (Heller), don. M. Berggren, Kristineberg Marine Biol. Stn., Sweden (published by Berggren, M., 1990. J. Crust. Biol 10(3): 554–558). VANUATU: 1 specimen (rmnh.crus.d.58064), stn FR06, NW Tutuba Island, 15°19’33”S 167°10’06”E, 13.ix.2006, depth unknown, scuba diving, hand picked, in Herdmania sp., fcn. CF35.

Diagnosis (based on Berggren, 1990). Small-sized shrimp. Rostrum falling short of the distal segment of the antennular peduncle, slightly depressed, acute, dorsally thickened, without distinct lateral carinae, without dorsal nor ventral teeth. Antennal spine present, small. Hepatic spine well-developed, small, mobile, far below level of antennal spine. Inferior orbital angle distinct, produced. Antero-lateral angle of carapace slightly rounded, slightly produced. Anterior margin of carapace between ventral orbital angle and antero-lateral angle straight. Sixth abdominal segment with posterolateral angle acute, posteroventral angle feebly acute. Telson with large dorsal spines at 0.35 and 0.50 of telson length, lateral pair of terminal spines just behind intermediate pair, distal margin of telson rounded, without median process. Basal segment of antennular peduncle with one small distolateral tooth. Scaphocerite with lateral margin almost straight, slit between small distolateral tooth and lamina shallow. Chela of first pereiopods spatulate, with cutting edges minutely pectinate along entire rim. Second pereiopods unequal, almost straight dactylus barely exceeding fixed finger on both chelae, without teeth on cutting edges, palm without tympanal organ. Ambulatory dactyli biunguiculate, with large broad distoventral process on flexor margin of corpus; unguis simple, acute, minute microstructures present on dorsal margin. Distoventral spines on ambulatory propodi long, club-shaped.

Colour (fig. 17). Whitish/opaque with small red dots scattered over the carapace, abdomen, and chelae of the second pereiopods (Berggren, 1990).

Hosts. Known from various species of ascidians. Pyuridae: Herdmania momus (Savigny, 1816) (Horká et al., 2016); Herdmania pallida (Heller, 1878) (Lebour, 1938); Pyura stolonifera (Heller, 1878) (Berggren, 1990); unidentified ascidian (Bruce, 1981c). Now recorded for the first time from Styelidae: Polycarpa sp. and Ascidiidae: Phallusia sp.

Distribution. Known from various regions of the Indo-West Pacific and the Indian Ocean: Ponta Torres, Inhaca Island (approximately 26°S, 33°W), Mozambique (Berggren, 1990); Gulf of Mannar, India (Lebour, 1938); Heron Island, Australia (Bruce, 1981c); Indonesia (Chow et al., 2021); Bali, Indonesia (Horká et al., 2016); Sabah, Malaysia (Horká et al., 2016). Now recorded for the first time from Vanuatu (Tutuba Island), and the following new localities in Indonesia: N, SW, and NE Sulawesi; Ambon, the Mollucas; Halmahera; Seribu (Thousand Islands); and Raja Ampat, West Papua.

Genus Ensiger Borradaile, 1915

ZooBank: urn:lsid:zoobank.org:act:012A13F1-C8A9-4C9F-B4E7-E8B5EE345560

Ensiger Borradaile, 1915: 207. Type species, being the first species subsequently placed in this subgenus, which was described without any nominal species: Anchistia aurantiaca Dana, 1852 (a junior subjective synonym of Cancer custos (Forskål, 1775); first placed in Ensiger by Borradaile, 1917. The genus is herein resurrected. Gender: masculine. Etymology: Borradaile (1915, 1917) did not provide information on the derivation of the name. From ensiger (Latin) = sword-bearer; probably in reference of the sword-like rostrum of the type-species.

Both the type species, Anchistus custoides Bruce, 1977, and Anchistus custos (Forskål, 1775) are herein transferred to Ensiger Borradaile, 1915.

Diagnosis. Moderately sized shrimps of subcylindrical body form. Rostrum well developed, compressed, without teeth or with very shallow indistinct dorsal teeth, lateral carinae feebly developed. Carapace smooth, glabrous; orbit feebly developed, inferior orbital angle distinct, antennal spine present, supraorbital, hepatic and epigastric spines absent, anterolateral margin somewhat produced, rounded. Abdomen smooth, glabrous, third segment not posterodorsally produced, anterior pleura rounded, posterior blunt. Telson with two pairs of small dorsal spines, three pairs of posterior spines. Eye small, cornea globular. Antennula normal, with basal peduncular segment with distolateral tooth, upper flagellum biramous, short ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed, with moderately developed distolateral tooth. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp, laciniae broad; maxilla with simple palp, basal endite broad, bilobed, coxal endite obsolete, scaphognathite broad; first maxilliped with slender palp, basal endite broad, fused with coxal endite, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod subrectangular, without podobranch; third maxilliped, ischiomerus and basis fused broad, exopod with numerous plumose setae distally, coxa with oval lateral plate, with or without rudimentary arthrobranch. Fourth thoracic sternite without median process. First pereiopods slender, chelae cannulate or sub-cannulate, with fingers subspatulate, cutting edges minutely pectinate. Second pereiopods well developed, similar, unequal, dactylus with large acute triangular tooth in proximal half, fixed finger with series of teeth in proximal part; propodus without tympanal organ. Ambulatory pereiopods with simple dactyli, without basal protuberance; unguis simple, without dorsal pad of fine scale-like spinules. Uropod with protopodite posterolaterally acute, exopod with small mobile distolateral spine.

Key to the species of Ensiger

1. 1.Chela first pereiopod sub-cannulate; rostrum with minute dorsal and distal shallow teeth; antennal spine well developed; dactylus of chela second pereiopod with one or two small teeth in proximal half..............................E. custoides
2. –Chela first pereiopod cannulate; rostrum devoid of dorsal and distal teeth; antennal spine minute; dactylus of chela second pereiopod with large triangular tooth in proximal half...................E. custos

Ensiger custoides (Bruce, 1977)

(figs. 20A–C, 21–22)

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A–C) Ensiger custoides (Bruce, 1977) in Atrina vexillum (Born, 1778). A) rmnh.crus.d.58065, stn raj.08; B) rmnh.crus.d.58066, stn ser.24; C) rmnh.crus.d.53610, stn ter.36; D) Ensiger custos (Forskål, 1775) from Pinna bicolor Gmelin, 1791, rmnh.crus.d.41446, stn rbe.01.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

photographs by c.h.j.m. fransen

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Ensiger custoides (Bruce, 1977), rmnh.crus.d.41440, ovigerous female pocl. 9.1 mm. A) habitus, lateral view; B) anterior appendages, lateral view; C) idem, dorsal view; D) telson, dorsal view. Scale A= 4 mm; B, C, = 2 mm; D = 1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Ensiger custoides (Bruce, 1977). A, B, E) rmnh.crus.d.41440, ovigerous female pocl. 9.1 mm. C, D) rmnh.crus.d.41444, ovigerous female pocl. 6.5 mm. A) right major second pereiopod chela; B) left minor second pereiopod chela; C) left major second pereiopod, medial view; D) right minor second pereiopod, medial view; E) right third pereiopod dactylus, medial view, propodal setae omitted. Scale A, B, D = 1 mm; C = 2 mm; E = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Anchistus inermis – Kubo, 1940: 48–51, figs. 15–17.

Anchistus custos – Holthuis, 1952: 106 (pro parte); Miyake & Fujino, 1968: 415–417.

Anchistus custoides Bruce, 1977a: 47, figs. 4–6 [Type locality: north-west end, Gillett Cay, Great Barrier Reef, 21°43’S 152°25’E, in bivalve mollusk Atrina vexillum according to Springthorpe & Lowry, 1994]; Bruce, 1981c: 2-3; Bruce, 1983b: 892; Bruce, 1983c: 199 (listed); Bruce, 1990: 15, 18 (listed); Müller, 1993: 7 (listed); Bruce, 1993: 56; Chace & Bruce, 1993: 72 (listed); Fransen, 1994a: 108, 110, 111 (listed); Britayev & Fachrutdinov, 1994: 124, fig. 2D-F; De Grave, 1999: 128, fig. 2; Li, 2000: 7, fig.7 (listed); Hayashi, 2002: 222, figs. 432c–e, 434c, d, 435c, d; Bruce, 2003b: 210 (listed); Hayashi, 2006: 115; Marin & Savinkin, 2007: table 2, 3 (listed); Bruce, 2010a: 63 (listed); De Grave & Fransen, 2011: 340 (listed); Fransen & Reijnen, 2012; Gan et al., 2015: 3, fig. 1; Anker & De Grave: 2016: 406, fig. 72; Horká et al., 2016: 6, figs. 1m, 2–4; Chow et al., 2021: table A.1 (listed); Idris et al., 2022: 136–148, figs. 4–5.

Material examined. INDONESIA: 1 ovigerous female pocl. 9.09 mm (rmnh.crus.d.41440), Snellius ii Expedition sta. 4.079, E of Komodo, Selat Linta, 8°35’S 119°34.2’E, 18.ix.1984, snorkeling, coastal reef flat, in large Pinna sp. (also collected). – 1 male pocl. 5.79 mm (rmnh.crus.d.41441), Java, off Jakarta, Seribu Archipelago, Kongsi Island, 26.vi.1973, sandy bottom, coll. Sapri D, don. pppo. – 1 ovigerous female pocl. 6.17 mm (rmnh.crus.d.41442), Java, off Jakarta, Seribu Archipelago, Pari Island, 27.i.1973, coll. Sukardi, don. pppo. – 1 ovigerous female pocl. 8.47 mm (rmnh.crus.d.41443), Seram Island, Piru Archipelago, Piru Bay, 03°04’45”S 128°11’27”E, 10.vi.1975, coll. A.H. Banner & D.M. Banner, Rumphius ii Expedition, don. pppo, fcn. cm 334. – 1 ovigerous female pocl. 6.49 mm (rmnh.crus.d.41444), Ambon Island, Ambon Bay, Tantoci, 3.vi.1975, coll. M.K. Moosa, A.H. Banner & D.M. Banner, Rumphius ii Expedition, don. pppo, fcn. cm 195. – 1 ovigerous female pocl. 9.22 mm (rmnh.crus.d.8996), Kera Island near Timor, 11-13.xi.1929, Snellius I Expedition 1929-1930, published in Holthuis, 1952: 106 as Anchistus custos. – 1 ovigerous female pocl. 6.2 mm (rmnh.crus.d.46640), stn sul.10, N Sulawesi, Selat Lembeh, Pulau Lembeh, W of Kelapadua, 01°26’N 125°13’E, 17.x.1994, large Acropora field, scuba diving to 20 m, in Atrina vexillum (Born), coll. J. Goud. – 1 ovigerous female pocl. 7.4 mm, 1 male pocl. 3.4 mm (rmnh.crus.d.46641), SW Sulawesi, Spermonde Archipelago, Pulau Badi, nnw side, depth 30 m, scuba diving, 3.x.1994, in Atrina vexillum (Born) (Ø 35 cm), coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 7.5 mm (rmnh.crus.d.46643), SW Sulawesi, Spermonde Archipelago, Barang Lompo, NW side, 23.ix.1994, depth 20 m, scuba diving, in A. vexillum (Ø 25 cm), coll. B.W. Hoeksema. – 1 ovigerous famel pocl. 5.6 mm, 1 male pocl. 2.6 mm (rmnh.crus.d.53610; GenBank OQ603090 (coi)), stn ter.36, off Halmahera mainland, Teluk Dodinga E, N of Pulau Jere, 0°50’47.8”N 127°37’48.7”, 13.xi.2009, depth 2 m, scuba diving, muddy bay shallow area with coral cover and rubble, in A. vexillum, coll. A. Gittenberger, fcn. CF-00123, photo ter.36.0086-91. – 2 ovigerous females pocl. 5.7 and 7.0 mm, 1 male pocl. 3.9 mm (rmnh.crus.d.53615), stn ter.38, off Halmahera mainland, Teluk Dodinga, Karang Galiasa Besar E, 0°50’45.6”N 127°35’7.4”E, 14.xi.2009, depth 2 m, scuba diving, exposed shallow reefflat followed by a sloping reef with coral and rubble,in A. vexillum, coll. C.H.J.M. Fransen, fcn. cf-00128, photo ter.38.0048-57. – 1 ovigerous female pocl. 9.0 mm, 1 male pocl. 3.5 mm (rmnh.crus.d.49844; GenBank OQ600398 (16S)), stn bal.32, Bali, N side of Nusa Penida, off Tukad Adegan, 08°40’32”S 115°31’18”E, 20.iv.2001, scuba diving to 30 m depth, deep reef slope with patches of sand, in large Atrina sp., coll. Angus, film 32. – 1 male pocl. 4.6 mm, 2 ovigerous females pocl. 5.9 and 8.2 mm (rmnh.crus.d.58029), stn lem.29, NE Sulawesi, Lembeh Strait, Teluk Walemetodo, 1°24’11.3394”N 125°10’20.3154”E, 15.ii.2012, depth 5 m, in each pair in an A. vexillum, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl.8.4 mm, 1 male pocl. 4.5 mm (rmnh.crus.d.58065), stn raj.08, W Papua, Raja Ampat Islands, Mioskon Island, 00°29.808’S 130°43.623’E, 21.xi.2007, depth 3 m, scuba diving, in A. vexillum, coll. B.W. Hoeksema, fcn. CF025. – 1 ovigerous female pocl. 5.5 mm (rmnh.crus.d.58066), stn ser.24, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Kotok Kecil Island, NW-side, 5°41’20”S 106°32’01”E, 16.ix.2005, depth 15 m, scuba diving, in A. vexillum, coll. C.H.J.M. Fransen, photo film 11. – 1 ovigerous female pocl. 8.5 mm (rmnh.crus.d.58067), stn ser.30, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Tikus Island, S-side, 5°51’55”S 106°34’55”E, 18.ix.2005, depth 20 m, scuba diving, in A. vexillum, coll. C.H.J.M. Fransen, photo film 16. – 1 male pocl. 4.0 mm (rmnh.crus.d.58068), stn ser.30, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Tikus Island, S-side, 5°51’55”S 106°34’55”E, 18.ix.2005, depth 20 m, scuba diving, in A. vexillum, coll. C.H.J.M. Fransen, photo film 16. – 1 male pocl. 4.6 mm, 1 ovigerous female pocl. 7.0 mm (rmnh.crus.d.58069), stn ber.06, NE Kalimantan, Berau Islands, shoal between Lighthouse-2 reef and Derawan Island, 02°12’08.6”N 118°11’34.9”E, 5.x.2003, depth 10 m, scuba diving, in A. vexillum, coll. C.H.J.M. Fransen. MALAYSIA: 1 male pocl. 3.3 mm (rmnh.crus.d.53810; GenBank JX185712), stn sem.24, Sabah, Semporna area, Bumbun Isl., 04°26’54.1”N 118°46’31.0”E, 7.xii.2010, depth 3 m, scuba diving, in A. vexillum, coll. B.T. Reijnen. – 1 male pocl. 3.6 mm (rmnh.crus.d.53795; GenBank JX185710), sta. sem.22, Sabah, Semporna area, Mata Pahi Isl., 04°27’40.7”N 118°38’09.1”E, 5.xii.2010, depth 3 m, scuba diving, in A. vexillum, coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 3.4 mm (rmnh.crus.d.53807; GenBank OQ603091 (coi)), stn sem.56, Sabah, Semporna area, Silawa Isl., 04°34’29.8”N 118°33’59.6”E, 17.xii.2010, depth 4 m, scuba diving, in A. vexillum, coll. C.H.J.M. Fransen. PHILIPPINES: 1 male pocl. 3.2 mm, 1 ovigerous female pocl. 5.9 mm (rmnh.crus.d.48353), Stn ceb.12, Cebu Strait, W of Bohol, NE side of Sandingan Island, 9°51.53’N 123°48.81’E, 15.xi.1999, depth 3–5 m, scuba diving, sand with coral patches, in Atrina pectinata (L.), coll. C.H.J.M. Fransen. – 1 male pocl. 3.9 mm, 1 ovigerous female pocl. 5.3 mm (rmnh.crus.d.48352), Stn ceb.12, Cebu Strait, W of Bohol, NE side of Sandingan Island, 9°51.53’N 123°48.81’E, 15.xi.1999, depth 3–5 m, scuba diving, sand with coral patches, in A. pectinata, coll. C.H.J.M. Fransen. VANUATU: 2 males pocl. 4.7 and 4.9 mm, 3 females pocl. 7.8, 8.5 and 9.4 mm (rmnh.crus.d.58070), stn DR11, Aoré Island, off port Lautour, 15°21’58”S 167°06’02”E, 12.ix.2006, scuba diving, hand picked, 2 pairs and a single female in 3 A. vexillum – 1 ovigerous female pocl. 7.5 mm, 1 male pocl. 4.5 mm (rmnh.crus.d.58071), stn db13, no further data, 13.ix.2006, depth unknown, scuba diving, in Atrina sp., coll. C.H.J.M. Fransen, fcn. CF29, photo T.-Y. Chan. – 1 ovigerous female pocl. 7.6 mm (rmnh.crus.d.58072), stn FR12, S Aoré Island, W Ratua Island, 15°22’07”S 167°06’17”E, 15.ix.2006, depth 0–3 m, snorkeling, in A. vexillum, coll. C.H.J.M. Fransen, fcn. CF51. – 2 ovigerous females pocl. 6.5 and 7.7 mm (rmnh.crus.d.58073), stn H1, Vanuatu maritime College, 22.ix.2006, hand picked, intertidal, mangrove environment, in 2 separate bivalves. – 1 ovigerous female pocl. 9.0 mm, 1 male pocl. 4.7 mm (rmnh.crus.d.58074), stn DR68, no further data, 26.ix.2006.

Diagnosis. Rostrum broad proximally, compressed distally, almost triangular in dorsal view, strongly bent downwards (especially in females), reaching distal segment of antennular peduncle, with 4–8 obtuse dorsal distal teeth, ventral margin unarmed, distally rounded, lateral carina feebly developed. Inferior orbital angle produced. Antennal spine present. Antero-lateral angle of the carapace broadly rounded, produced. Anterior margin of carapace between ventral orbital angle and antero-lateral angle sinuate. Sixth abdominal segment with posterior ventral angle acute. Telson with dorsal spines at 0.75 and 0.88 of length. Basal segment of antennular peduncle with one or two distolateral teeth, lateral margin slightly convex. Scaphocerite with convex lateral margin; shallow slit between distolateral spine and lamina. Third maxilliped with robust penultimate segment and broad antepenultimate segment. Basis and ischium of first pereiopod with row of long slender setae along their ventral margins; chela sub-cannulate, slightly sub-spatulate, palm with row of long plumose setae on opposite sides; cutting edges minutely pectinate in distal half. Second pereiopods relatively small with slender fingers; dactylus with one or two small teeth in proximal half; fixed finger with 4–7 small teeth in proximal half; palm without tympanal organ. Ambulatory pereiopods with dactylus simple, not biunguiculate; reflected margin of corpus with transverse ridges; unguis sparsely provided with small triangular flattened scale-like spinules.

Remarks. The female specimen collected at sta. 4.079 of the Snellius ii expedition (rmnh.crus.d.41440) shows two closely set distolateral teeth on the basal segment of the antennular peduncle (fig. 21C). The same specimen has bifurcated tips on the intermediate pair of terminal spines of the telson (fig. 21D) The specimen collected at Kongsi Island (rmnh.crus.d.41441) has two teeth on the left and one tooth on the right basal segment of the antennal peduncle, while the other specimens have one distolateral tooth on both sides as described for the type material (Bruce, 1977a: 47). The second pereiopods are usually small in relation to the carapace length and subequal.

Re-examination of Snellius I material described by Holthuis, 1952 yielded one ovigerous female (rmnh.crus.d.8996) identified as A. custos which belong to A. custoides.

Colour (figs. 20A–C). Specimens are translucent with numerous small red and white chromatophores all over the body, giving it an orange appearance. The cornea is strongly reflecting, colouring silver.

Hosts. Recorded from Pinnidae: Atrina vexillum (Born, 1778) (Miyake & Fujino, 1968; Bruce, 1977a, 1981c; De Grave, 1999; Hayashi, 2002, 2006; Fransen & Reijnen, 2012; Idris et al., 2022); Pinna atropurpurea G.B. Sowerby I, 1825 (Anker & De Grave, 2016); Pinna bicolor Gmelin, 1791 (Britayev & Fachrutdinov, 1994; De Grave, 1999; Hayashi, 2006; Idris et al., 2022); Pinna deltodes Menke, 1843 (Idris et al., 2022); Pinna muricata L., 1758 (Idris et al., 2022); Pinna sp. (Bruce, 1993). Also from Pteriidae: Pteria (Avicula) sp. (Bruce, 1983c). Now for the first time recorded from Atrina pectinata (L., 1767).

Distribution. Gillett Cay, Swains Reefs, One Tree Island, Capricorn Group, Australia (Bruce, 1977a); Heron Island, Australia (Bruce, 1981c); Caroline Islands, Palau (Kubo, 1940; Miyake & Fujino, 1968); Seram Island, Indonesia (Bruce, 1983c); Sabah, Malaysia (Fransen & Reijnen, 2012); Johor, W Malaysia (Idris et al., 2022); Singapore (Anker & De Grave, 2016); Tre Island, Vietnam (Bruce, 1993); Hainan, China (Gan et al., 2015); Okinawa, Japan (Horká et al., 2016); Japan (Hayashi, 2002, 2006). Now recorded for the first time from various localities in Indonesia: Ambon Island, Kera Island near Timor, Selat Linta E of Komodo, the Seribu Archipelago off North Java, Bali, NE and SW Sulawesi, Teluk Dodinga (off mainland Halmahera), W Papua (Raja Ampat), and NE Kalimantan (Berau Islands). Additionally, now also newly recorded from Vanuatu and the Philippines (Cebu Strait).

Ensiger custos (Forskål, 1775)

(figs. 20D, 23–27)

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Ensiger custos (Forskål, 1775). A–C) rmnh.crus.d. 41446, ovigerous female pocl. 6.5 mm; D–F) rmnh.crus.d.41445, male pocl. 4.0 mm. A) habitus, ectina view; B) anterior appendages, lateral view; C) idem, dorsal view; D) tailfan, dorsal view; E) telson, tip, dorsal view; F) disolateral part uropodal exopod, ectin view. Scale A= 4 mm; B, C, = 2 mm; D = 2 mm; E, F = 0.25 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Ensiger custos (Forskål, 1775). rmnh.crus.d.41445, male pocl. 4.0 mm. A) antennula, dorsal view; B) left mandible, ventral view; C) left maxillula, ventral view. Scale = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Ensiger custos (Forskål, 1775). rmnh.crus.d.41445, male pocl. 4.0 mm. A) left antenna, ventral view; B) left third maxilliped, ventral view. Scale = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Ensiger custos (Forskål, 1775). rmnh.crus.d.41445, male pocl. 4.0 mm. A) left first maxilliped, ventral view; B) left second maxilliped, ventral view. Scale = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Ensiger custos (Forskål, 1775). A–C) rmnh.crus.d.41445, male pocl. 4.0 mm. A) left first pereiopod, lateral view; B) right second pereiopod chela, medial view; C) left second pereiopod chela, medial view; D, rmnh.crus.d.41448, ovigerous female pocl. 6.4 mm, right third pereiopod dactylus, medial view, propodal setae omitted. Scale A = 1 mm; B, C = 1 mm; D = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Restricted synonymy:

Cancer custos Forskål, 1775: 94 [Type locality: Lohajæ, intra Pinna nigras].

Pontonia inflata H. Milne Edwards, 1840 [in H. Milne Edwards, 1834-1840]: 633 [Type locality: Ceylan et sur les côtes de Vanicoso].

Anchistia aurantiaca Dana, 1852a: 25 [Type locality: archipelago Viti].

Harpilius inermis Miers, 1884: 291, pl. 32 fig. B [Type locality: Port Molle, in the interior of a shell of a species of Pinna]; Müller, 1887: 471.

Pontonia pinnae Ortmann, 1894: 16, pl. 1 fig. 3; nec Lockington, 1878a [Type locality: Dar-es-Salaam, Chokirbank, in den Schalen einer Pinna-Art]

Anchistus inermis – Borradaile, 1898: 387 (listed); Lanchester, 1902: 565; Pearson, 1905: 77; Rathbun, 1914: 656; Borradaile, 1917: 388 (listed); Tattersall, 1921 (listed); Hale, 1927: 57, fig. 52.

Pontonia custos – Borradaile, 1898: 388 (listed).

Periclimenes aurantiacus – Borradaile, 1898: 382 (listed).

Marygrande mirabilis Pesta, 1911: 573, figs. 1–5 (partim) [Type locality: Samoa]; Pesta, 1913: 88, figs. 31, 32; De Grave, 2001: 129–134, figs. 1–3.

Periclimenes (Ensiger) aurantiacus – Borradaile, 1917: 376 (listed).

Pontonia spinax Dawydoff, 1952: 136. [nomen nudum]

Anchistus custos – Holthuis, 1955: 62, fig. 34 (listed); Holthuis, 1952: 105–109 (full synonymy), figs. 43, 44 (specimen from Kera Island excluded (= Ensiger custoides (Bruce, 1977)); Johnson, 1961: 59; Johnson & Liang, 1966: 433–455, figs. 1–10; Jacquotte, 1963: 59–62; Hipeau-Jacquotte, 1967: 153–166; McNeill, 1968; Hipeau-Jacquotte, 1971: 194; Bruce, 1972a: 219 (listed); Hipeau-Jacquotte, 1972a: 287–294, figs. 1, 2a₁; Hipeau-Jacquotte, 1973a: 96–116, figs. 1a1–f1, 2, 3a1–b1, 4a1–d1,5, 6a, 7a1–f1, 8a1–d1; Hipeau-Jacquotte, 1973b: 63-70; Hipeau-Jacquotte, 1974a: 367-382; Hipeau-Jacquotte, 1974b: 383-402; Hipeau-Jacquotte, 1974c: 403–408; Hipeau-Jacquotte, 1974d: 359–386; Thomassin, 1974: 306; Bruce, 1975a: 150, 160–162, fig. 7; Bruce, 1976a: 93; Bruce, 1976d: 464; Bruce, 1976e: 447; Bruce, 1977a: 47; Bruce, 1977b: 174; Bruce, 1978b: 279; Bruce, 1979a: 231–232; Johnson, 1979: 31; Tirmizi & Kazmi, 1982: 115–117; Bruce, 1982: 264–265, fig. 19; Bruce, 1983a: 44; Bruce, 1983c: 199 (listed); Bruce & Svoboda, 1983: 36 (listed); Vine, 1986: 101 (listed); Bruce, 1989: 178; Bruce, 1990: 15, 18 (listed); Bruce, 1993: 56; Chace & Bruce, 1993: 72 (listed); Müller, 1993: 8 (listed); Fransen, 1994a: 106, 108, 111, fig. 4; Britayev & Fachrutdinov, 1994: 126, figs. 3A–C, 4–5; Bruce & Coombes, 1995: 106; Bruce, 1996: 205; Davie, 1998: 96, unnumbered colour photo; Davie, 2002: 305 (listed); De Grave, 1999: 129, fig. 3, pl. 1b–c; Li, 2000: 7, fig. 8 (listed); Li, 2001: 76; De Grave, 2001: 129–134, figs. 1-3; Hayashi, 2002: 21, fig. 433, 434e, f; Li & Liu, 2002: 271–272, fig. 1; Li et al., 2004: 528; Li & Bruce, 2006: 625; Bruce, 2006: table 1 (listed); Hayashi, 2006: 115; Marin & Savinkin, 2007: table 2 (listed); De Grave, 2007: 145 (listed); Li et al., 2007: 176, fig. 73 (listed); Li, 2008a: 235, fig. 2; De Grave & Fransen, 2011: 340 (listed); De Grave & Ashelby, 2011: table 1 (listed); Dobson et al., 2014: suppl. fig. 1, appendix 1; Kou et al., 2015: table 1, fig. 1; Gan et al., 2015: 3, fig. 1; Hosie et al., 2015: 283 (listed); Dobson et al., 2016: fig. 7, suppl. inf. I; Anker & De Grave, 2016: 406, fig. 73; Samuel et al., 2016: table 1; Ghory & Kazmi, 2018: 23–26; Al-Kandari et al., 2020, 263, fig. 8; Chow et al., 2021: table A.1.

Not Anchistus custos – Miyake & Fujino, 1968: 415 (= Ensiger custoides (Bruce, 1977)).

Not Pontonia custos – Sharp, 1893: 119 (= Pontonia pinnophylax (Otto, 1821)).

Material examined. INDONESIA: 1 male pocl. 4.03 mm (rmnh.crus.d.41445), stn rbe.01, Ambon Island, Ambon Bay, inner bay, Hunut, basecamp, 28.xi.1990, depth 1-3 m, snorkeling, in Pinna sp., coll. H.L. Strack. – 1 ovigerous female pocl. 6.49 mm (photo M.S.S. Lavaleye 51/23-27). – 1 male pocl. 5.65 mm (photo M.S.S. Lavaleye 51/25-29) (rmnh.crus.d.41446), stn rbe.01, Ambon Island, Ambon Bay, inner Bay, Hunut, basecamp, 11.xii.1990, depth 10 m, scuba diving, in large Pinna bicolor Gmelin, coll. C.H.J.M. Fransen. – 1 male pocl. 3.83 mm, 1 ovigerous female pocl. 6.10 mm (rmnh.crus.d.41447), stn rbe.35, Ambon Island, Ambon Bay, Martafons, 4.xii.1990, littoral collecting, from wreck, in Pinna sp., coll. H.L. Strack. – 1 ovigerous female pocl. 6.36 mm (rmnh.crus.d.41448), stn rbe.35, Ambon Island, Ambon Bay, inner bay, Martafons, 4.xii.1990, depth 2–4 m, snorkeling, from piles of lightbouy, in Pinna [or Atrina?], coll. J.C. den Hartog. – 1 male pocl. 3.18 mm (rmnh.crus.d.41449), sta. 35, Ambon Island, Ambon Bay, inner bay, Martafons, 5.xii.1990, depth 1–3 m, snorkeling, from piles of lightbouy, in oyster [or Atrina?], coll. C.H.J.M. Fransen and J.C. den Hartog. – 2 males pocl. 5.06, 5.26 mm (rmnh.crus.d.41450), Java, off Jakarta, Seribu Archipelago, Tikus Island, 23.vii.1978, depth 1-2 m, in Pinna sp., coll. Sikardi, don. pppo. – 2 males pocl. 5.00, 6.29 mm, 3 ovigerous females pocl. 8.44, 8.70, 9.61 mm (rmnh.crus.d.41451), Pulau Seribu Archipelago, 29.xi.1984, in P. bicolor, coll. Sapri, Don. pppo. – 1 male pocl. 5.32 mm, 1 ovigerous female (damaged) (rmnh.crus.d.41452), Java, off Jakarta, Seribu Archipelago, Kongsi Island, 25.v.1972, intertidal, dead coral and sand, coll. M.K. Moosa & Sitabatan, don. pppo, fcn. CM 7. – 1 male pocl. 6.75 mm (rmnh.crus.d.41453), Java, off Jakarta, Seribu Archipelago, Pari Island, 27.i.1973, in Pinna sp., coll. Sukardi, don. pppo. – 1 male pocl. 5.00 mm (rmnh.crus.d.41454) Ambon Island, Ambon Bay, Tantoci, 3.vi.1975, coll. M.K. Moosa, A.H. Banner & D.M. Banner, don. pppo, fcn. CM 195. – 4 males pocl. 5.58, 5.84, 6.10, 6.23 mm, 3 ovigerous females pocl. 7.27, 7.27, 7.33 mm (rmnh.crus.d.41455), near east coast of Tegal Island, near Sunda Island, in Pinna sp., 16.i.1983, coll. Indra & Sukardi, don. pppo. – 1 ovigerous female pocl. 5.84 mm (zma.crus.D.101.612), Siboga Expedition stn 127, Sangihe Group, Siau Island, anchorage off Sawan, 18/19.vii.1899, depth 27 m (publ. Holthuis, 1952: 106). – 1 male pocl. 6.17 mm, 1 female pocl. 11.04 mm, 1 ovigerous female pocl. 7.14 mm (zma.crus.D.101.613), Lesser Sunda Islands, 18.xii.1909, leg. H.J.M. Laurense (publ. Holthuis, 1952: 106). – 1 non ovigerous female pocl. 3.5 mm (rmnh.crus.d.58075), stn ser.01, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Onrust Island, NW-side, 6°02’01”S 106°43’58”E, 7.ix.2005, depth 1–2 m, scuba diving and snorkeling, in P. bicolor, coll. P.G. Rachello Dolmen. – 6 males pocl. 5.1, 5.3, 5.7, 5.9, 6.5 and 6.5 mm, 6 ovigerous females 7.0, 7.5, 7.7, 8.1, 8.7 and 8.8 mm (rmnh.crus.d.57963; GenBank OQ603092 (coi) & OQ600399 (16S)), stn ser.01, Java Sea, Kepulauan Seribu (Thousand Islands), 6°02’01”S 106°43’58”E, 7.ix.2005, depth 1–2 m, scuba diving and snorkeling, in in Atrina ectinate (L.), coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 6.4 mm (rmnh.crus.d.58076), stn ser.02, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Damar Besar Island, NW-side, 5°57’17”S 106°50’27”E, 8.ix.2005, depth 5 m, scuba diving and snorkelling, in A. ectinate, coll. C.H.J.M. Fransen. – 1 male pocl. 5.1 mm (rmnh.crus.d.58077), stn ser.02, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Damar Besar Island, NW-side, 5°57’17”S 106°50’27”E, 8.ix.2005, depth 7 m, scuba diving and snorkelling, in A. ectinate, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 5.3 mm, 1 male pocl. 3.7 mm (rmnh.crus.d.58078), stn ser.02B, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Damar Besar Island, NW-side, 5°57’17”S 106°50’27”E, 8.ix.2005, depth 2 m, scuba diving and snorkelling, in P. bicolor, coll. J. Goud. – 1 ovigerous female pocl. 4.3 mm (rmnh.crus.d.58079), stn ser.03, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Damar Kecil Island, NW-side, 5°59’00”S 106°50’43”E, 8.ix.2005, depth unknown, scuba diving and snorkelling, in P. bicolor, coll. J. Goud. – 3 ovigerous females pocl. 5.0, 5.7 and 6.4 mm, 3 males pocl. 4.5, 4.7 and 5.4 mm (rmnh.crus.d.58080), stn ser.07, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Bidadari Island, NW-side, 6°01’55”S 106°44’47”E, 9.ix.2005, depth 2–3 m, scuba diving and snorkelling, in P. bicolor, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 6.8 mm, 1 male pocl. 4.4 mm (rmnh.crus.d.58081), stn ser.08, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Ayer Besar Island, NW-side, 6°00’06”S 106°46’48”E, 10.ix.2005, depth 3 m, scuba diving and snorkelling, in P. bicolor, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 6.2 mm, 1 male pocl. 5.2 mm (rmnh.crus.d.58082), stn ser.10, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Kelor Island, NW-side, 6°01’31”S 106°44’39”E, 20.ix.2005, depth 2–3 m, scuba diving and snorkelling, in P. bicolor, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 6.9 mm, 1 male pocl. 5.1 mm (rmnh.crus.d.58083), stn ser.10, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Kelor Island, NW-side, 6°01’31”S 106°44’39”E, 20.ix.2005, depth 2–3 m, scuba diving and snorkelling, in P. bicolor, coll. B.W. Hoeksema. – 1 ovigerous female pocl. 6.8 mm, 1 male pocl. 4.7 mm (rmnh.crus.d.58084), stn ser.10, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Kelor Island, NW-side, 6°01’31”S 106°44’39”E, 20.ix.2005, depth 2–3 m, scuba diving and snorkelling, in P. bicolor, coll. P.G. Rachello Dolmen. – 1 ovigerous female pocl. 7.7 mm, 1 male pocl. 5.8 mm (rmnh.crus.d.58085), stn ser.10, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Kelor Island, NW-side, 6°01’31”S 106°44’39”E, 20.ix.2005, depth 1-2 m, scuba diving and snorkelling, in P. bicolor, coll. R. Moolenbeek. – 1 ovigerous female pocl. 8.5 mm, 1 male pocl. 5.5 mm (rmnh.crus.d.52028), stn ser.13, Pulau Seribu Archipelago, Lancang, 5°55’37”S 106°35’29”E, 12.ix.2005, depth 12 m, in P. bicolor, Pulau Seribu. – 1 ovigerous female pocl. 3.9 mm, 1 male pocl. 3.6 mm (rmnh.crus.d.58086), stn ser.14, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Bokor Island, NW-side, 5°56’35”S 106°37’38”E, 12.ix.2005, depth 10 m, scuba diving and snorkelling, in P. bicolor, coll. P.G. Rachello Dolmen. – few specimens (rmnh.crus.d.58087), stn ser.20, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Sepa Island, W-side, 5°34’39”S 106°34’48”E, 14.ix.2005, unknown depth, scuba diving from jetty (night), in P. bicolor, coll. C.H.J.M. Fransen. – few specimens (rmnh.crus.d.58058), stn ser.20, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Sepa Island, W-side, 5°34’39”S 106°34’48”E, 14.ix.2005, unknown depth, scuba diving from jetty (night), in P. bicolor coll. C.H.J.M. Fransen. – 1 male pocl. 6.5 mm, 1 ovigerous female pocl. 8.6 mm (rmnh.crus.d.46642), SW Sulawesi, Spermonde Archipelago, Gusung, NW side, 7.x.1994, depth 8 m, scuba diving, in Atrina vexillum (Born) (Ø 35 cm), coll. B.W. Hoeksema. – 1 male, pocl. 5.6 mm, 1 female pocl. 6.9 mm (rmnh.crus.d.47464), stn mal.01, Moluccas, Ambon, Inner bay, N coast near laboratory Poka, 03°38’S 128°11’E, 1-4.xi.1996, depth 1–2 m, snorkeling, muddy sublittoral near rocky shore, in P. bicolor, coll. C.H.J.M. Fransen. – 3 ovigerous females pocl. 7.9, 7.8 and 7.3 mm, 2 males pocl. 6.0 and 7.0 mm (rmnh.crus.d.42649), Padando Gr., Konori, Mios Woendi, New Guinea, in Pinna sp., ex. Natural Science Foundation, no. 464 and no. 00112. – 1 specimen, total length 24 mm (zma.crus.D.101612), Anchorage off Sawan, Siau Islands, 18.vii.1899, Siboga Expedition. – 1 ovigerous female total length 28 mm, 1 specimen, total length 27 mm (zma.crus.D.101613), Tual Anchorage, Kei Islands, 12.xii.1899, Siboga Expedition. MALAYSIA: 2 males pocl. 4.74, 5.00 mm, 1 female pocl. 5.00 mm, 1 ovigerous female pocl. 5.32 mm (rmnh.crus.d.41456), Lankawi, Pantai [= beach] Kok, 22.ix.1991, littoral collecting, depth 0.1–0.2 m, each pair in Pinna sp., in one Pinna together with pinnotherid crab, coll. H.L. Strack. SINGAPORE: 1 female pocl. 8.44 mm (rmnh.crus.d.41288), near Sentosa Island, -vi.1983, tidal zone, in Pinna sp. (Ø 15cm), coll. P.K.L. Ng. TAIWAN: 1 ovigerous female pocl. 9.09 mm (rmnh.crus.d.4162), S Taiwan, Takao, 15.ix.1907, in Pinna sp., coll. H. Sauter. JAPAN: 1 male pocl. 4.1 mm, 1 female pocl. 5.4 mm (rmnh.crus.d. 56147), Ryukyu Islands, Okinawa, Yagai Island, 19.ix.2013, intertidal, in Pinna sp., coll. Yoshida, Ryuta. PERSIAN GULF: 2 males pocl. 6.10, 6.23 mm, 2 ovigerous females pocl. 8.05, 8.83 mm (rmnh.crus.d.16550), off Zeel Island, near stn 2, 26.ix.1956, coll. C.E. Dawson. – 1 male pocl. 5.4 mm (rmnh.crus.d.48723), Oman, Masicoh, C2, no more data, don. MNHN, Paris through A. Anker, 2000. MADAGASCAR: 1 male pocl. 4.87 mm (rmnh.crus.d.16546), Esimipoika Bay, on gills of Pinna sp., coll. G. Petit, don. Zool. Staatssammlung München. – 1 male pocl. 4.74 mm (rmnh.crus.d.16547), Normandia, don. Zool. Staatssammlung München. – 1 male pocl. 6.88 mm, 1 female pocl. 7.79 mm (rmnh.crus.d.16548), province of Tuléar, Ankalibé, 1906, coll. F. Geay, don. Zool. Staatssammlung München. – 1 ovigerous female pocl. 9.09 mm (rmnh.crus.d.16549), province of Tuléar, 1921, coll. G. Petit, don. Zool. Staatssammlung München. UNKNOWN LOCALITY: 1 ovigerous female pocl. 8.05 mm (rmnh.crus.d.4163), in Pinna sp., coll. M.J. Landauer (publ. Holthuis, 1952: 106).

Diagnosis. Rostrum broad proximally, compressed distally, oblong triangular in dorsal view, distally rounded, bent downwards, reaching distal end of ultimate segment of antennular peduncle, without teeth. Small antennal spine present. Ventral orbital angle produced. Antero-lateral angel of carapace rounded, slightly produced. Sixth abdominal segment posterior ventral angle rounded. Telson with minute dorsal spines at 0.60 and 0.82 of telson length. Basal segment of antennular peduncle with one distolateral tooth. Scaphocerite with convex lateral margin; shallow slit between distolateral tooth and lamina. Stylocerite blunt. Third maxilliped with narrow penultimate segment and very broad antepenultimate segment. Basis and ischium of first pereiopod with row of long slender setae on ventral margins; chela slightly sub-spatulate, cannulate, palm with rows of long slender plumose setae on opposite margins; cutting edges minutely pectinate along distal 2/3. Second pereiopods well developed; chela robust; dactylus with concave outer margin and large triangular tooth in proximal half of cutting edge; fixed finger with 3–6 small teeth in proximal half; palm without tympanal organ. Ambulatory dactyli simple, sparsely provided with flattened scale-like spinules on unguis.

Remarks. The specimens of this well-known species show no aberrant features.

Colour (fig. 20D). Specimens are translucent with numerous small red and white chromatophores all over the body, giving it an orange appearance. The cornea is strongly reflecting, colouring silver.

Hosts. Recorded from Pinnidae: Atrina vexillum (Born, 1778) (Forskål, 1775 (as Pinna nigras); Kemp, 1922 (as Pinna vexillum Born, 1778 and Pinna nigra Chemnitz, 1785), 1925 (as P. nigra); Jacquotte, 1963; Hipeau-Jacquotte, 1967, 1973a, 1973b, 1974b; Britayev & Fachrutdinov, 1994; Hayashi, 2006 (also as P. nigra); Li, 2008a); Pinna atropurpurea G. B. Sowerby I, 1825 (Johnson & Liang, 1966; Bruce, 1979a; Hayashi, 2002, 2006; Anker & De Grave, 2016); Pinna bicolor Gmelin, 1791 (Kemp, 1922; Jacquotte, 1963; Hipeau-Jacquotte, 1967, 1973b, 1974b; Bruce, 1976b, 1976c; 1976d, 1976e, 1978b, 1993; Britayev & Fachrutdinov, 1994; Bruce & Coombes, 1995; De Grave, 1999; Hayashi, 2002, 2006; Li, 2008a; Al-Kandari et al., 2020); Pinna deltodes Menke, 1843 (Bruce & Coombes, 1995; Hayashi, 2006 as ‘Pinna deltoides’); Pinna dolabrata Lamarck, 1819 (Hale, 1927; Hayashi, 2006); Pinna madida Reeve, 1858 (Hedley, 1924; Hayashi, 2006); Pinna muricata L., 1758 (Jacquotte, 1963; Hipeau-Jacquotte, 1967, 1974b; Bruce, 1976d, 1976e, 1978b, 1978c; Hayashi, 2006); Pinna sp. (Miers, 1884; Ortmann, 1894; Rathbun, 1914; Holthuis, 1952; Johnson, 1961; McNeill, 1968; Bruce, 1989, 1993; Bruce & Coombes, 1995; Li, 2001; Li & Liu, 2002; Li et al., 2004); Streptopinna saccata (L., 1758) (Forskål, 1775, as Pinna saccata; Forskål, 1775; Hayashi, 2002, 2006). Also recorded from Turbinellidae: Vasum sp. (Bruce, 1996; Hayashi, 2006); Cardiidae (Tridacninae): Tridacna gigas (?) (L., 1758) (Pesta, 1911, 1913; Hayashi, 2006); and Isognomonidae: Isognomon isognomum (L., 1758) (Hayashi, 2006). In addition, one record from an ‘infra-branchial chamber of a large gastropod’ (Lanchester, 1902).

Now newly recorded from Atrina pectinata (L., 1767).

Distribution. Widely distributed in the Indo-Pacific, from the Red Sea south to Moçambique and Madagascar to Japan, the Philippines, eastward to Fiji. Lohajæ (= Al-Luhayya, Yemen), Red Sea (Forskål, 1775; Tattersall, 1921; Vine, 1986); Dar es Salaam, Tanzania (Ortmann, 1894); Madagascar (Jacquotte, 1963; Hipeau-Jacquotte, 1967, 1973b, 1974b, 1974c, 1974d, 1975b; Thomassin, 1974; Bruce, 1978b; Gan et al., 2015); Gulf of Mannar (Pearson, 1905; Bruce, 1976e); Sri Lanka (Müller, 1887); Kenya and Zanziber (Bruce, 1976d); Philippines (Bruce, 1989); Hong-Kong (Bruce, 1979a; Chow et al., 2021); Singapore (Johnson, 1961, 1979; Johnson & Liang, 1966; Anker & De Grave, 2016); Hainan Island, South China Sea (Li, 2001; Li & Liu, 2002; Li et al., 2004); Ambon, Indonesia (Fransen, 1994a); Bay of Jakarta, Indonesia (Holthuis, 1952); Kera, near Timor, Indonesia (Holthuis, 1952); Kai Island, Indonesia (Holtuis, 1952); Siau Island, Indonesia (Holthuis, 1952); Pulau Bidan, Penang, Malaysia (Lanchester, 1902); Australia (Bruce, 1977a); Queensland, Australia (Miers, 1884; McNeill, 1968; Bruce, 1977b); Moreton Bay, Australia (Li, 2008a; Kou et al., 2015); Monte Bello Islands, Australia (Rathbun, 1914); Tre Island, Vietnam (Bruce, 1993); South Vietnam (Britayev & Fachrutdinov, 1994); Papua New Guinea (De Grave, 1999); New Caledonia (Bruce, 1996); Fiji (Dana, 1852, as Viti); Takao, South Taiwan (Holthuis, 1952); Samoa (Pesta, 1911, 1913). Now for the first time recorded from these localities in Indonesia: Seribu Archipelago (Thousand Islands), Sunda Islands, SW Sulawesi, and New Guinea. Additionally, now also recorded from Okinawa, Japan; Masicoh, Oman; and Zeel Island (presumably Halat Za’al, Saudi Arabia).

Genus Neoanchistus Bruce, 1975

Neoanchistus Bruce, 1975a: 149. Type species, by original designation and monotypy: Neoanchistus cardiodytes Bruce, 1975. Gender: masculine.

Diagnosis (after Bruce, 1995: 83). Small sized shrimps of stout, depressed body form. Rostrum well developed, thickened, blunt, unarmed, lateral carinae indistinct. Carapace smooth, glabrous, inferior orbital angle and orbit obsolete, supraorbital, epigastric, hepatic and antennal spines absent. Anterolateral angel of carapace broadly rounded. Abdomen smooth, glabrous, pleura with posterior margins rounded. Telson narrow, with two pairs of minute dorsal spines and three pairs of posterior spines. Eye normal, with globular cornea. Antennula with basal segment of peduncle without distolateral tooth. Antenna with basicerite unarmed. Scaphocerite well developed with moderately sized distolateral tooth; slit between distolateral tooth and lamina shallow. Epistome unarmed. Mandible without palp, molar process robust, incisor process feeble; maxillula with feebly bilobed palp, laciniae normal; maxilla with simple palp, basal endite bilobed, scaphognathite moderately broad; first maxilliped with setose palp, basal endite broadly rounded, coxal endite fused to basal endite, exopod well developed, caridean lobe broad, exopod with plumose terminal setae, epipod bilobed; second maxilliped normal, dactylar segment narrow, exopod with terminal plumose setae, epipod subrectangular, without podobranch; third maxilliped with endopod slender, ischiomerus and basis fused, exopod flagellum with plumose terminal setae, coxa with oval lateral plate, arthrobranch rudimentary. Fourth thoracic sternite unarmed. First pereiopods slender, sub-spatulate, with cutting edges minutely pectinate. Second pereiopods small, subequal, similar, stout, dactylus hamate. Ambulatory pereiopods robust, dactyli hooked, unguis simple, large, with dorsal margin with minute scale-like spinules. Uropod with protopodite posterolaterally acutely produced, exopod with small mobile posterolateral spine.

Two species are recognized: Neoanchistus cardiodytes Bruce, 1975, and Neoanchistus nasalis Holthuis, 1986. Both species occur in bivalve hosts. The species can be distinguished as follows:

Key to the species of Neoanchistus

1. 1.Rostrum reaching end of antennular peduncle; outer antennular flagellum with two basal segments fused; dactyli of ambulatory pereiopods slender............................................................N. cardiodytes
2. –Rostrum reaching halfway second segment antennular peduncle; outer antennular flagellum with seven basal segments fused; dactyli of ambulatory pereiopods stout...........................N. nasalis

Neoanchistus cardiodytes Bruce, 1975

(fig. 28A)

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A) Neoanchistus cardiodytes Bruce, 1975, from an unknown species of Vasticardium Iredale, 1927 (det. J. Goud), Madang Lagoon, Papua New Guinea (mnhn-iu-2013-10029 stn. pr107); B, C) Neoanchistus nasalis Holthuis, 1986, from Mimachlamys townsendi (G.B. Sowerby iii, 1895), Oman (flmnh uf). B) ovigerous female; C) male.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

photographs by arthur anker

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Neoanchistus cardiodytes Bruce, 1975a: 149–165, figs. 1–6 [type locality: Nosy Bé, Madagascar]; Bruce, 1978b: 287; Müller, 1993: 39 (listed); Holthuis, 1993: 153, fig. 142 (listed); Fransen, 1994a: 111 (listed); Li, 2000: 81, fig. 81 (listed); Britayev & Marin, 2011: 1–3, fig. 1; De Grave & Fransen, 2011: 353 (listed).

Diagnosis. Rostrum stout, depressed, extending slightly beyond antennular peduncle, without teeth not setae, broadened in dorsal view by thick lateral expansions, distally truncated, proximally slightly constricted. Carapace without spines. Inferior orbital angle rounded, slightly produced. Anterolateral angle of carapace rounded, not produced. Abdomen smooth, glabrous, pleura with posterior margins rounded. Telson narrow, with two pairs of small dorsal spines at 0.6 and 0.8 of telson length and three pairs of posterior spines. Basal segment of antennular peduncle distolaterally rounded; outer flagellum fused in basal two segments, shorter free ramus two-segmented, longer ramus four-segmented. Scaphocerite with straight lateral margins; slit between distolateral tooth and lamina shallow. First pereiopods with chela sub-spatulate; lateral cutting edges proximally gaping, distally minutely pectinate; merus with peg-like spinules on inner margin of proximal part. Dactylus of second chela strongly hooked, overreaching fixed finger, with one small blunt tooth at about one-third of its length; fixed finger with a small tooth halfway the cutting edge. Ambulatory pereiopods without distoventral spines in propodus of third pereiopod, with simple slender dactyli; unguis with minute scale-like spinules dorsally.

Remarks. The tympanal organ in the proximal medio-ventral surface of the palm in the second pereiopods is not reported in the type-description. This feature however could have been overlooked.

Colour (fig. 28A). Bruce (1975a: 158): “Body covered dorsally with round or slightly irregular reddish markings, with margins darker than centres. Appendages with similar red stripes (A.G. Humes, in litt.).” Britayev & Marin (2011) published a colour photograph of the species.

Hosts. Recorded from Cardiidae, Trachicardiinae: Vasticardium pectiniforme (Born, 1780) (Bruce, 1975a (as Trachicardium/ Cardium pectiniforme Born, 1780)). Also from Mactridae: Mactra grandis Gmelin, 1791 (Britayev & Marin, 2011). Now recorded from an unidentified Vasticardium Iredale, 1927.

Distribution. Nosi Bé, Madagascar (Bruce, 1975a); Vietnam (Britayev & Marin, 2011). Now for the first time recorded from Madang Lagoon (stn. PR107; 05°10.2’S – 145°50.4’E), Papua New Guinea (A. Anker, pers. comm.; see fig. 28A).

Neoanchistus nasalis Holthuis, 1986

(fig. 28B, C, 29)

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Neoanchistus nasalis Holthuis, 1981. A) rmnh.crus.d.48724, non ovigerous female pocl. 4.0 mm; B–E) rmnh.crus.d.36608, ovigerus female, pocl. 14.3 mm. A) habitus, lateral view; B) left second pereiopod, ventral view; C) idem, chela, ovigerous female, pocl. 12.4 mm; D) idem, ovigerous female, pocl. 14.3 mm; D) left fifth pereiopod dactylus, lateral view. Scale A = 2 mm; B = 4 mm; C, D = 1 mm; E = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by w. de gier (a) and c.h.j.m. fransen (b–d)

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Neoanchistus nasalis Holthuis, 1986: 264-269, figs. 1-2 [type locality: artificial reef near Raysut Harbour, Dhofar, southern Oman, 16°57’45”N 54°00’E, in Chlamys townsendi (= Mimachlamys townsendi (G. B. Sowerby III, 1895))]; Hogarth, 1989: 111; Müller, 1993: 39 (listed); Fransen, 1994a: 107, 111, fig. 2f; Li, 2000: 81, fig. 82 (listed); Bruce, 2006: table 1 (listed); De Grave & Fransen, 2011: 353 (listed); Dobson et al., 2014: 9, appendix 1; Dobson et al., 2016: fig. 7, suppl. inf. I.

Neanchistus nasalis – Hogarth, 1989: 111 [erroneous spelling].

Material examined. INDIAN OCEAN: 1 male pocl. 9.8 mm, 2 ovigerous females pocl. 12.4 14.3 mm (rmnh.crus.d.36608), Southern Oman, Dhofar, artificial reef near Raysut Harbour, 16°57’45”N 54°00’E, 24.ii.1983, in Chlamys townsendi (G.B. Sowerby), coll. P.J. Hogarth, no. 41, site no. IJI. – 1 specimen, pocl. 10 mm (rmnh.crus.d.36608), Southern Oman, Raysut, 9.x.1983, depth 10 m, in C. townsendi, coll. P.J. Hogarth, no. 335. 1 non ovigerous female pocl. 4.0 mm (rmnh.crus.d.48724), Oman, Masicoh, C1, no more data, don. MNHN, Paris through A. Anker, 2000.

Diagnosis. Rostrum stout, depressed, extending halfway second segment antennular peduncle, without teeth nor setae, broadened in dorsal view by thick lateral expansions, distally rounded, proximally not constricted. Carapace without spines. Inferior orbital angle strongly produced. Anterolateral angle of carapace broadly rounded, produced. Basal segment of antennular peduncle distolaterally rounded; outer flagellum fused in basal seven segments, shorter free ramus with about four segments. Scaphocerite with almost straight lateral margins; slit between distolateral tooth and lamina shallow. First pereiopods with sub-spatulate, densely setose chela; lateral cutting edges proximally gaping, distally minutely pectinate; merus without peg-like spinules on inner margin of proximal part. Palm of second pereiopods with oblong oval tympanal organ in proximal two-third to three-fourth of medio-ventral surface; dactylus of second chela strongly hooked, overreaching fixed finger, one large triangular tooth at about one-third of its length; fixed finger with 10–12 small teeth in the proximal half of which the distalmost largest. Ambulatory pereiopods with propodi with distoventral spines, with simple stout dactyli, with one, seldom two, minute accessory teeth; unguis with minute scale-like spinulation dorsally.

Remarks. Dactyli of ambulatory pereiopods are very similar to those of Tympanicheles pectinis, both with a minute accessory tooth, dorsal transverse rims on the corpus, and dorsally minutely spinulate unguis. Chela of second pereiopods show differences in setation of the fixed finger, in two specimens it is provided with a dense cover of long setae on the ventral margin (fig. 29C), in the largest chela the number of setae is much smaller.

Colour (fig. 28B, C). Similar pattern as the other species in the genus. The colouration patterns on the appendages is, however, different from N. cardiodytes. In N. cardiodytes, the spotted pattern forms connected, continuous ‘bands’, most visible in the major chelipeds and walking legs. In N. nasalis, the spots are distinguishable and separated from each other.

Host. Pectinidae: Mimachlamys townsendi (G.B. Sowerby, 1895) (Holthuis, 1986; Hogarth, 1989; Fransen, 1994a).

Distribution. Type-locality: Raysut, Southern Oman (cf. Holthuis, 1986; Hogarth, 1989; Fransen, 1994a). Now recorded for the second time from Oman (fig. 28B, C).

Genus Paranchistus Holthuis, 1952

Paranchistus Holthuis, 1952: 5, 13, 91. Type species, by original designation: Anchistus biunguiculatus Borradaile, 1898 (a junior subjective synonym of Pontonia armata H. Milne Edwards, 1837). Gender: masculine.

Diagnosis. Large sized shrimps of subcylindrical body form. Rostrum well developed, compressed, with or without indistinct shallow dorsal and distal teeth, lateral carinae feebly developed. Carapace smooth, glabrous; orbit feebly developed, inferior orbital angle distinct, slightly produced, antennal spine well developed, basally broad; hepatic, spine, if present, small, articulating; supraorbital and epigastric spines absent; anterolateral margin rounded, slightly produced. Abdomen smooth, glabrous, third segment not posterodorsally produced, anterior pleura rounded, posterior blunt. Telson with two pairs of dorsal spines in distal half, three pairs of posterior spines. Eye small, cornea globular. Antennula normal, upper flagellum biramous, short ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed with distolateral tooth. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp; maxilla with simple palp, basal endite broad, bilobed, proximal lobe much smaller than distal lobe, coxal endite obsolete, scaphognathite broad; first maxilliped with palp, basally broad, distally slender, basal endite broad, well separated from coxal endite by suture, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod bilobed; second maxilliped with normal endopod, dactylar segment slender, concave, exopod well developed, broad, coxa medially slightly produced, epipod rectangular, without podobranch; third maxilliped with endopod slender, ischiomerus and basis partly fused, exopod with numerous plumose setae distally, coxa with oval lateral plate, with rudimentary arthrobranch. Fourth thoracic sternite without median process. First pereiopods slender, chelae with fingers spatulate, non-cannulate, lateral cutting edges minutely pectinate. Second pereiopods well developed, similar, subequal, dactylus strongly hooked, overreaching fixed finger, with three broad teeth in proximal half, fixed finger with series of teeth in proximal part; propodus without ventral oval tympanal organ proximally. Ambulatory pereiopods with biunguiculate dactyli, with large triangular accessory tooth, with without basal protuberance; unguis compressed, curved, with few scattered minute scale-like spinules; propodi with strong distoventral spines. Uropod with protopodite posterolaterally acutely produced, exopod with small mobile distolateral spine, without distolateral tooth.

The genus is monospecific with Pontonia armata H. Milne Edwards, 1837 (= Paranchistus armatus (H. Mile Edwards, 1837)) as its type species. Paranchistus liui Li, Bruce & Manning, 2004, Paranchistus nobilii Holthuis, 1952, Paranchistus pycnodontae Bruce, 1978, and Paranchistus spondylis Suzuki, 1971 are herby transfered to Polkamenes. Paranchistus ornatus Holthuis, 1952 is transfered to Tympanicheles.

Paranchistus armatus (H. Milne Edwards, 1837)

(figs. 30–32)

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Paranchistus armatus (H. Milne Edwards, 1837), rmnh.crus.d.46092. A–E, H) ovigerous female, pocl. 13.8 mm; F, G, I, J) male, pocl. 8.7 mm. A) habitus, lateral view; B) anterior appendages, lateral view; C) idem, dorsal view; D), antennal spine and infraorbital angle; E, F) rostrum, lateral view; G) telson, dorsal view; H) left second pereiopod chela; I) right fifth pereiopod dactylus, medial view; J) idem, detail unguis. Scale A = 8 mm; B, C = 4 mm; E–G = 2 mm; D = 1 mm; I = 0.4; J = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Paranchistus armatus (H. Milne Edwards, 1837), rmnh.crus.d.46092, ovigerous female, pocl. 13.8 mm. A) left mandible, ventral view; B) right maxillula, ventral view; C) right maxilla, ventral view; D) right first maxilliped, ventral view. Scale A = 0.5 mm; B–D = 1.25 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Paranchistus armatus (H. Milne Edwards, 1837), rmnh.crus.d.46092, ovigerous female, pocl. 13.8 mm. A) right second maxilliped, ventral view; B) right third maxilliped, ventral view. Scale = 0.5 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Pontonia armata H. Milne Edwards, 1837: 359 [type locality: près de côtes de la Nouvelle-Irlande]; Broderip, 1841: 421 (listed); Lucas, 1851: 183; Sharp, 1893: 119 (listed).

Anchistus biunguiculatus Borradaile, 1898: 387; Borradaile, 1900: 408, pl. 36 fig. 5; Borradaile, 1917: 388; Hayashi, 2005: 515.

Anchistus? armatus – Borradaile, 1898: 387 (listed); Borradaile, 1917: 389 (listed).

Tridacnocaris biunguiculata – Nobili, 1899: 235 [type locality: British New Guinea].

Anchistus oshimai Kubo, 1949: 26, figs. 1, 2 [type locality: Helen Atoll].

Paranchistus biunguiculatus – Holthuis, 1952: 13, 93, figs. 36–38; Holthuis, 1953: 56; Holthuis, 1955: 62, fig. 32b (listed); Rosewater, 1965: 370; McNeill, 1968: 21; Miyake & Fujino, 1968: 417; Suzuki, 1971: 110; Bruce, 1972a: 221 (listed); Bruce, 1975a: 162 (listed); Bruce, 1975b: 27; Bruce, 1976f: 59 (listed); Devaney & Bruce, 1987: 230 (listed).

Anchistus armatus – Bruce, 1967: 564; Hipeau-Jacquotte, 1972b: 9.

Paranchistus armatus – Bruce, 1975c: 49-54, figs. 1-3; Bruce, 1979a: 226–227; Bruce, 1983c: 204; Bruce, 1986: 165; Devaney & Bruce, 1987: 230 (listed); Bruce, 1990: 16, 18 (listed); Holthuis, 1993; 160, fig. 151; Müller, 1993: 10 (listed); Chace & Bruce, 1993: 90-91 (listed); Fransen, 1994a: 111 (listed); De Grave, 1999: 134, pl.2 fig. a; Bruce, 2000: 91-96, figs. 1-2; Li, 2000: 110, fig. 119 (listed); De Grave & Fransen, 2011: 357 (listed).

Material examined. INDONESIA: 1 male pocl. 8.70 mm, 1 ovigerous female pocl. 13.77 mm (rmnh.crus.d.46092; GenBank OQ600400 (16S)), Kei Islands, Tanimbar, 16.xi.1990, depth 8–10 m, scuba diving, in large Tridacna gigas (L.) (Ø 50cm), coll. Zainal. – 1 male pocl. 5.80 mm (rmnh.crus.d.8991), Moluccas, Obi Latu, shore and reef, 23-27.iv.1930, Siboga Expedition, published by Holthuis, 1952: 93–97, figs. 36–38, as Paranchistus biunguiculatus.

Diagnosis. See diagnosis of genus.

Remarks. In smaller specimens the dorsal teeth on the rostrum are more prominent with setae in between, in larger specimens the teeth become indistinct (Bruce, 1975c: 5). This indicates that the dorsal rostral teeth become less prominent after each moult this in contrast to Anchistus australis and Tympanicheles ornatus where they are placed more distally after each moult. The hepatic spine is normally developed in small specimens and reduced or absent in larger specimens.

The dactylus of the ambulatory pereiopods is very different from those of other species in the ‘Anchistus group’. With E. custos and E. custoides it has in common the sparcely distributed scale-like spinules on the unguis, whereas in other species the unguis is densely covered with spinules on the dorsal surface. The broad robust accessory tooth is very different from the slender simple or minutely spinulate accessory tooth in A. miersi, Polkamenes nobilii, P. pycnodontae, P. spondylis, or the minute accessory tooth in A. demani, A. australis, N. nasalis, Tympanicheles ornatus, and T. pectinis.

Colour. Various colour descriptions are known. “Great Barrier Reef specimens were noted to be transparent or whitish. Freshly preserved specimens showed a dense covering of minute red chromatophores all over the body, with similar but more sparse dots over de second pereipods.” (cf. Bruce, 1975c: 51). “The ovigerous female in life is transparent or light blue with dark blue spots except for the carapace, in which they are enclosed with white rings. The cornea is bitter orange, and the stalk is light blue. The antennal flagellum is reddish purple. The colour of the male is unknown.” (cf. Miyake & Fujino, 1968: 417). “Body generally translucent whitish in colour, generally and evenly with numerous small white and inconspicuous chromatophores. Ovary a deep olive green. Antennal peduncles and eyestalks whitish. Cornea white. Pereiopods whitish, finely spotted with red. Caudal fan whitish, more heavily speckled with red.” (cf. Bruce, 1979b: 227). From the present specimens was noted that the carapace was more or less translucent and the antennae were blue.

Hosts. Only known from giant clams (Cardiidae: Tridacninae): Tridacna gigas (L., 1758) (Kubo, 1949; Rosewater, 1965; McNeill, 1968; Bruce, 1975c, 1979a, 1983b; De Grave, 1999). Several authors recorded the species from Tridacna sp. (Borradaile, 1917; Holthuis, 1952; Bruce, 1975c, 1979b).

Distribution. Same presumed distribution as its host: Tridacna gigas (L., 1758), e.g., Moluccas, Indonesia to the Marshall Islands. NE Australia (cf. McNeill, 1968; Bruce, 1975c); Marshall Islands (Holthuis, 1953; Rosewater, 1965; Bruce, 1975c, 1979b); Eniwetok Atoll (Rosewater, 1965); Obi latu, Moluccas, Indonesia (Holthuis, 1952); Aru Islands, Indonesia (Holthuis, 1993); Batanta and Numfoor Island, New Guinea, Indonesia (Nobili, 1899); Papua New Guinea (De Grave, 1999); New Ireland, Papua New Guinea (cf. H. Milne Edwards, 1837; Bruce, 1975c); Tubetube, Engineer Islands, Papua New Guinea (Borradaile, 1898); ‘British New Guinea’ (southeastern part of Papua New Guinea) (Borradaile, 1898); Helen Atoll, Ngaianges Island and Ngadarak Reef, Palau Islands (Kubo, 1940, 1949; Miyake & Fujino, 1968). Now newly reported from a second locality in the Mollucas: Kei Islands, Tanimbar.

Genus Polkamenes gen. nov.

ZooBank: urn:lsid:zoobank.org:act:7AE1F106-EED4-499E-8D49-9BAFB5235D9A

Diagnosis. Small to moderately sized shrimps of subcylindrical body form. Rostrum well developed, compressed, with teeth in distal part, lateral carinae feebly developed. Carapace smooth, glabrous; orbit feebly developed, inferior orbital angle distinct, antennal spine present, supraorbital and epigastric spines absent, hepatic spine mobile, anterolateral margin not or feebly produced. Abdomen smooth, glabrous, third segment not posterodorsally produced, anterior pleura rounded, posterior blunt. Telson with two pairs of dorsal spines, three pairs of posterior spines. Eye small, cornea globular. Antennula normal, proximal segment of peduncle with distolateral tooth, upper flagellum biramous, flagella short, short ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp, laciniae normal or broad; maxilla with simple palp, basal endite broad, bilobed, coxal endite obsolete, scaphognathite broad; first maxilliped with slender palp, basal endite broad, fused to coxal endite, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod bilobed; second maxilliped with normal endopod, flagellum with numerous plumose setae distally, epipod subrectangular, without podobranch; third maxilliped with endopod slender, ischiomerus distinct from basis, exopod with numerous plumose setae distally, coxa with oval lateral plate, with rudimentary arthrobranch. Fourth thoracic sternite without median process. First pereiopods chelae with fingers sub-spatulate, cutting edges entire or minutely pectinate. Second pereiopods well developed, similar, unequal, dactylus with large acute triangular tooth in proximal half, fixed finger with series of teeth in proximal part; propodus without ventral oval tympanal organ proximally. Ambulatory pereiopods with simple or biunguiculate dactyli, without basal protuberance; unguis with dorsal pad of fine scale-like spinules. Uropod with protopodite posterolaterally acute, exopod with small mobile distolateral spine.

Etymology. ‘Polkamenes’: named after the characteristic blue-, red-, and orange-dotted pattern seen on the species’ carapace, abdomen, and appendages ‘Polka dots’ (English, in combination with the common palaemonid suffix ‘-menes’; see e.g., Ancylomenes Okuno & Bruce, 2010, Laomenes Clark, 1919, Periclimenes). Gender: masculine.

Type species by present designation: Paranchistus pycnodontae Bruce, 1978 (= Polkamenes pycnodontae (Bruce, 1978)).

We recognize four species: Polkamenes liui (Li, Bruce & Manning, 2004); Polkamenes nobilii (Holthuis, 1952); Polkamenes pycnodontae (Bruce, 1978); and Polkamenes spondylis (Suzuki, 1971). All have bivalve hosts. The latter three species, with the biunguiculate ambulatory dactyli, are very similar. Polkamenes nobilii and P. spondylis are only known from a few specimens and dna sequences could only be obtained from P. pycnodontae. It thus remains unclear if the differences presently used to distinguish these nominal species are indeed species specific or mere intraspecific variation. If more material becomes available, for both morphological and molecular phylogenetic analyses, it will be possible to determine with more certainty if these three nominal species are indeed separate biological species. The species can be distinguished as follows:

Key to the species of Polkamenes

1. 1.Ambulatory pereiopods with dactyli simple, not biunguiculate..................P. liui
2. –Ambulatory pereiopods with dactyli biunguiculate.................................................2
3. 2.First pereiopod chela with cutting edges minutely pectinate......................................3
4. –First pereiopods with cutting edges entire, not minutely pectinate....................................................................P. spondylis
5. 3.Anterior margin of basal segment of antennular peduncle rounded; accessory tooth of ambulatory dactyli not ventrally bifurcate..............P. pycnodontae
6. –Anterior margin of basal segment of antennular peduncle with tooth; accessory tooth of ambulatory dactyli usually ventrally bifurcate..........................P. nobilii

Polkamenes liui (Li, Bruce & Manning, 2004)

Paranchistus liui Li, Bruce & Manning, 2004: 535, figs. 21–23 [type locality: [21°N 108°E, 30 m]; Li et al., 2007: 247, fig. 119 (listed); De Grave & Fransen, 2011: 357 (listed).

Diagnosis (based on Li, Bruce & Manning, 2004). Rostrum slightly ventral directed, reaching distal margin of basal segment of antennular peduncle, dorsal and ventral margins subparallel, apex blunt in lateral view, with one distodorsal tooth and one apical tooth which situated at the below middle of the apex. Carapace with small antennal spine; with small articulating hepatic spine situated in depression somewhat posteroventrally of antennal spine; inferior orbital angle produced; anterolateral angle rounded, not produced. Telson with two pairs of small dorsal spines at 0.60 and 0.76 of telson length. Basal segment of antennular peduncle with one distolateral tooth. Scaphocerite well developed with slightly convex lateral margin; distolateral tooth normal, almost reaching the distal margin of the lamina; slit between distolateral tooth and lamina shallow. First pereiopods slender, chela sub-spatulate, cutting edge of fingers entire. Second pereiopods equal in size and form; fingers of equal length; dactylus with one large tooth in proximal half; fixed finger with five small teeth in proximal half; palm flattened. Ambulatory pereiopods with dactyli compressed, unguis not flattened, with sparse fine tubercles on extensor surface, ventral margin simple, not biunguiculate, corpus with distal margin slightly deeper than base of unguis. Protopodite of uropods with strong acute lateral tooth; lateral margin of uropod exopod slightly convex, distolateral with mobile spine.

Colour. Unknown (Li et al., 2004).

Hosts. Unknown (Li et al., 2004).

Distribution. Only known from the type locality in the South China Sea, China (21°N 108°E).

Remarks. The cutting edge of the chela of the first pereiopods is without minute denticulation (Li et al., 2004). As all species in the ‘Anchistus clade’ possess a minute denticulation on the cutting edges of the first pereiopod chelae, this would be a reversion to the ancestral state. As only one small specimen is known, more material is needed to check if this character is typical for the species.

Polkamenes nobilii (Holthuis, 1952)

(fig. 34)

Anchistus Miersi – Nobili, 1906a: 48; Pérez, 1920: 1027. (Not A. miersi (De Man, 1888)).

Paranchistus nobilii Holthuis, 1952: 100–104, figs. 41, 42 [type locality: Arzana Island, Rakas Zakoum Bank, Persian Gulf, out of Spondylus gaederopus]; Suzuki, 1971: 110; Bruce, 1972a: 221 (listed); Bruce, 1975c: 162 (listed); Bruce, 1977a: 47; Bruce, 1983b: 890, figs. 6E, 8I, J; Müller, 1993: 51 (listed); Chace & Bruce, 1993: 91 (listed); Fransen, 1994a: 107, 111, text-fig. 2h; Li, 2000: 111, fig. 120 (listed); De Grave & Ashelby, 2011: table 1 (listed); De Grave & Fransen, 2011: 357 (listed).

Anchistus gravieri – McNeill, 1953: 89. (Not A. gravieri Kemp, 1922).

Material examined. PERSIAN GULF: 2 males pocl. 3.96 mm, 2 ovigerous females pocl. 5.78 mm, cotypes (zma.crus.D.102828), Rakas Zakoum Bank, Arzana Island, 1901, in Spondylus gaederopus L., coll. C. Pérez, collection J.G. den Man.

Diagnosis. Rostrum well developed, laterally compressed in distal part, straight, almost reaching end of second segment of antennular peduncle, with 5–7 dorsal distal teeth and 0-1 ventral distal tooth; row of setae between dorsal teeth. Carapace with antennal spine well developed; articulating hepatic spine present, situated in depression somewhat posteroventrally of antennal spine; inferior orbital angle slightly produced; anterolateral angle rounded, slightly produced. Telson with two pairs of small dorsal spines at 0.62 and 0.82 of telson length. Basal segment of antennular peduncle with two distal teeth in males, one distolateral tooth and strongly convex anterior margin in females; outer flagellum with basal five segments fused, free shorter ramus of two or three segments. Scaphocerite well developed with almost straight lateral margin; distolateral tooth normal, almost reaching distal margin of lamina, sometimes just overreaching distal margin of lamina; slit between distolateral tooth and lamina shallow. First pereiopod slender, chela sub-spatulate, minutely pectinate in distal two-thirds of lateral margin. Second pereiopods subequal in shape and size; dactylus overreaching fixed finger, with one large triangular tooth in proximal half, densely setose on lateral margin; fixed finger with 4–6 small teeth in proximal half. Ambulatory pereiopods with biunguiculate dactyli; slender accessory tooth usually ventrally bifurcate, more or less covered with minute scale-like spinules; unguis dorsally flattened, with dense cover of minute scale-like spinules. Uropods with protopodite with strong acute lateral tooth; lateral margin of exopod convex with small mobile spine distolaterally.

Remarks. Reexamination of the type specimens yielded some additional morphological data. The first pereiopods have the cutting edges pectinate (fig. 34I) in the distal part, this in contrast with Holthuis (1952: 102) who stated that they were not pectinate. The accessory tooth on the ambulatory pereiopods is more or less provided with minute scale-like spinules and bifurcate ventrally. The basal segment of the antennular peduncle has two teeth distolaterally in the males; in the females one distolateral tooth is present while the distal margin is is strongly convex, overreaching the distolateral tooth. The lateral posterior spines of the telson are relatively long in the small males compared with the larger females, in which they are more of the size of Bruce’s specimen (Bruce, 1983b: fig. 6E).Teeth on the rostrum are regarded dorsal when setae are in between them. The ventral side of the rostrum does not bear a row of setae.

Polkamenes spondylis (Suzuki, 1971) is only differing from the present species in having a stouter accessory tooth in the dactylus of the ambulatory pereiopods. According to the original description, the chela of the first pereiopods are not sub-spatulate and have entire cutting edges, but Suzuki’s illustration (fig. 8a) shows the accessory tooth of the ambulatory pereiopods to be minutely spinulate. This should be checked with the holotype. The species may be con-specific with Polkamenes nobilii Holthuis, 1952.

Colour. The colouration of the type-specimens of P. nobilii is unknown.

Hosts. Recorded as Parachistus nobilii from Spondylus gaederopus L., 1758 (Nobili, 1906a: Pérez, 1920; Holthuis, 1952; Fransen, 1994a); Tridacna sp. (Bruce, 1983b); Pinna sp. (McNeill, 1953).

Distribution. Rakas Zakoum Bank, Arzana Island, Persian Gulf (Nobili, 1906a; Pérez, 1920; Holthuis, 1952; Fransen, 1994a); Gilbert Islands (McNeill, 1953); Seram Island, Mollucas, Indonesia (Bruce, 1983b).

Polkamenes pycnodontae (Bruce, 1978)

(figs. 33, 35)

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Polkamenes pycnodontae (Bruce, 1978). A) rmnh.crus.d.48261, from Hyotissa hyotis (L., 1758); B) rmnh.crus.d.54136, in Pteria penguin (Röding, 1798); C)rmnh.crus.d.54139, in P. penguin; D) rmnh.crus.d.57918, stn raj.14, in Lopha sp.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Polkamenes nobilii (Holthuis, 1952). A-C, E, H-L) zma.crus.D.102.828, ovigerous female, pocl. 5.8 mm; D) idem, pocl. 5.8 mm; F) male, pocl. 4.0 mm; G) male, pocl. 4.0 mm. A) habitus, lateral view; B) anterior appendages, dorsal view; C) idem, lateral view; D–G) rostrum, lateral view; H) telson, dorsal view; I) left first pereiopod chela, lateral view; J) right second pereiopod chela, lateral view; K) left third pereiopod dactylus, lateral view; L) left fifth pereiopod distal part dactylus and unguis, lateral view. Scale A = 4 mm; B, C = 2 mm; D-H, J = 1 mm; I = 0.4 mm; K, L = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Polkamenes pycnodontae (Bruce, 1978). A–C, E, K) rmnh.crus.d.48262, ovigerous female, pocl. 3.3 mm; L) idem, non ovigerous female, pocl. 3.1 mm; M) idem, non ovigerous female, pocl. 3.3 mm; G, N–Q) idem, male, pocl. 2.1 mm; I) male, pocl. 2.2 mm; D, R, S) rmnh.crus.d.48261, ovigerous female, pocl. 3.9 mm; I) rmnh.crus.d.48263, male pocl. 2.8 mm; J) rmnh.crus.d.48266, male, pocl. 2.7 mm; H) idem, male, pocl. 2.5 mm; F) idem ovigerous female, pocl. 3.4 mm. A) habitus, lateral view; B) anterior appendages, dorsal view; C) idem, lateral view; D–J) rostrum, lateral view; K) tail fan, dorsal view; L, M) telson, dorsal view; N) thorax, ventral view; O) left first pereiopod, lateral view; P) left second pereiopod, ventral view; Q) idem, chela, medial view; R) left third pereiopod, lateral view; S) idem, dactylus. Scale A = 4 mm; B, C, K = 2 mm; D–J, L, M, N = 1 mm; O, P, R = 1 mm; Q = 0.4 mm; S = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

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Paranchistus pycnodontae Bruce, 1978c: 233–243, textfigs. 1–5, pl. 39 [type locality: Heron Island, Capricorn Group, Queensland, 3 m]; Bruce, 1980: 180, text-fig. 16, pl. 1 fig.; Bruce, 1981c: 9; Bruce, 1983c: 204 (listed); Bruce, 1990: 16, 18 (listed); Müller, 1993: 51 (listed); Fransen, 1994a: 111; De Grave, 1999: 138, fig. 6, pl. 2b–g; Li, 2000: 112, fig. 122; Li, 2008b: 218; Bruce, 2010a: 64 (listed); Poupin & Juncker, 2010: 276, fig. 276b; De Grave & Fransen, 2011: 357 (listed); Baeza et al., 2013: 172–181, figs. 1–4; Dobson et al., 2014: 8, suppl. fig. 1, appendix 1; Dobson et al., 2016: fig. 7, suppl. inf. I; Horká et al., 2016: 6, figs. 2–4; Chow et al., 2021: table A.1.

Paranchistus serenei Bruce, 1983b: 890, figs. 7H, 9 [type locality: Seleman Bay, Seram Island]; Bruce, 1990: 18 (listed); Chace & Bruce, 1993: 91 (listed); Müller, 1993: 52 (listed); Strack, 1993: 58; Fransen, 1994a: 107, fig. 2e, 112, pl. 2: fig. 4; Poupin, 1998: 15; Li, 2000: 112, fig. 123.

Material examined. INDONESIA: 1 female pocl. 3.87 mm (rmnh.crus.d.48261), stn rbe.01, Moluccas, Ambon, Hitu, Ambon Bay, inner bay, W-side of Hunut (= 2 km N of Poka), in front of basecamp, 30.xi.1990, depth 12 m, scuba diving, in large Pteria sp., coll. C.H.J.M. Fransen, photo C.H.J.M. Fransen & M.S.S. Lavaleye 36/1-4. – 3 males pocl. 1.93, 2.47, 2.47 mm, 3 ovigerous females pocl. 3.33, 3.40, 4.00 mm (rmnh.crus.d. 48265), stn rbe.35, Moluccas, Ambon, Hitu, Ambon Bay, inner bay, Martafons, 4.xii.1990, depth 1–3 m, snorkeling, in oyster shells on piles, coll. C.H.J.M. Fransen & J.C. den Hartog, photo M.S.S. Lavaleye 41/34-35, 42/1. – 1 male pocl. 2.67 mm (rmnh.crus.d.48266), stn rbe.35, Moluccas, Ambon, Hitu, Ambon Bay, inner bay, Martafons, 4.xii.1990, depth 2–4 m, scuba diving, in the bivalve Vulsella vulsella (L.), coll. C.H.J.M. Fransen. – 2 males pocl. 2.13, 2.2 mm, 1 female pocl. 3.07 mm, 1 ovigerous female pocl. 3.25 mm (rmnh.crus.d.48262), stn rbe.35, Moluccas, Ambon, Hitu, Ambon Bay, inner bay, Martafons, 4.xii.1990, depth 4–6 m, snorkeling, in Pteria sp. shells on piles, coll. J.C. den Hartog. – 1 male pocl. 2.8 mm (rmnh.crus.d.48263), stn rbe.35, Moluccas, Ambon, Hitu, Ambon Bay, inner bay, Martafons, 4.xii.1990, depth 2-4 m, snorkeling, in Pteria sp. shells on piles, coll. J.C. den Hartog. – 2 males pocl. 1.8, 2.3 mm, 2 ovigerous females pocl. 3.3, 3.7 mm (rmnh.crus.d.48264), stn rbe.35, Moluccas, Ambon, Hitu, Ambon Bay, inner bay, Martafons, 4.xii.1990, depth 2–4 m, snorkeling, in oyster shells on piles, coll. J.C. den Hartog. – 1 ovigerous female pocl. 4.00 mm (rmnh.crus.d.48260), Snellius ii stn 4.069, E of Komodo, Teluk Slawi, northern cape of entrance, 8°36’S 119°31.2’E, 17.ix.1984, rocky shore adjacent to sandy beach. – 1 male pocl. 4.2 mm, 1 ovigerous female pocl. 4.0 mm (rmnh.crus.d.49845; GenBank OQ600401 (16S)), stn bal.26, Bali, N side Nusa Penida, off Desa Ped, 08°40’28”S 115°30’50”E, 21.iv.2001; depth 25 m, scuba diving, deep reef slope, in Pteria sp. (Ø 20cm) on Gorgonaria, coll. C.H.J.M. Fransen. – 1 male pocl. 2.9 mm (rmnh.crus.d.53612; GenBank OQ603093 (coi)), stn ter.37, off Halmahera Island, Teluk Dodinga E, NW of Pulau Jere, 0°50’26”N 127°37’54”E, 13.xi.2009, depth 18 m, scuba diving, in Pteria penguin (Röding) on rock, coll. C.H.J.M. Fransen, fcn. CF-00125, photo ter.37.0072-75. – 1 ovigerous female pocl. 2.9 mm (rmnh.crus.d.58089), stn. lem.27, NE Sulawesi, Lembeh Strait, S N Tanjung Pandean, 1°24’21.7074”N 125°10’4.5114”E, 14.ii.2012, depth 22 m, in P. penguin, coll. B.T. Reijnen. – 1 ovigerous female pocl. 2.2 mm (rmnh.crus.d.58090), stn lem.35, NE Sulawesi, Lembeh Strait, Batu Kapal, 1°32’56.832”N 125°17’31.848”E, 18.ii.2012, depth 22 m, in P. penguin (Ø 20 cm), coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 3.7 mm, 1 male pocl. 3.1 mm (rmnh.crus.d.58091), stn ser.06, Java Sea, Kepulauan Seribu (Thousand Islands), off Jakarta, Dapur Island, NW-side, 5°56’44”S 106°43’27”E, 9.ix.2005, unknown depth, scuba diving and snorkelling, in Hyotissa hyotis (L.), coll. C.H.J.M. Fransen, photo film 4. – 1 male pocl. 3.0 mm with abdominal bopyroids, 1 ovigerous female, pocl. 3.1 mm, (rmnh.crus.d.58092), stn ber.06, NE Kalimantan, Berau Islands, shoal between Lighthouse-2 reef and Derawan Island, 02°12’08.6”N 118°11’34.9”E, 5.x.2003, depth 10 m, scuba diving, in P. penguin (Ø 20 cm), coll. J. Goud. – 1 male pocl. 3.8 mm, 1 ovigerous female, pocl. 4.2 mm (rmnh.crus.d.58093), ber.05, NE Kalimantan, Berau Islands, Berau delta, Lighthouse-2 reef, 02°09’33.9”N 118°10’11.4”E, 5.x.2003, depth 5-8 m, scuba diving, in P. penguin (Ø 20 cm), coll. C.H.J.M. Fransen. – 1 male pocl. 1.3 mm (rmnh.crus.d.57918), stn raj.14, W Papua, Raja Ampat Islands, Akber Reef, 00°34.253’S 130°39.561’E, 23.xi.2007, depth 6 m, scuba diving, in Lopha sp., together with a pair of fish of the genus Onuxodon Smith (Carapidae), coll. J. van Egmond, fcn. CF054, photo. – 1 specimen (pleopods missing) pocl. 1.9 mm (rmnh.crus.d.54139), stn raj.14, W Papua, Raja Ampat Islands, Akber Reef, 00°34.253’S 130°39.561’E, 23.xi.2007, depth unknown, scuba diving, in P. penguin, coll. B.W. Hoeksema, fcn. CF055, photo. – 1 male pocl. 2.7 mm (rmnh.crus.d.54136), stn raj.15, W Papua, Raja Ampat Islands, SW Kri, Kuburan, 00°33.713’S 130°39.673’E, 23.xi.2007, depth unknown, scuba diving, in P. penguin, coll. B.W. Hoeksema, fcn. CF062, photo. – 1 male pocl. 2.9 mm (rmnh.crus.d.57920), stn raj.33, W Papua, Raja Ampat Islands, S Gam, E Besir Bay, 00°29.306’S 130°35.510’E, 29.xi.2007, depth 15 m, scuba diving, in P. penguin, coll. C.H.J.M. Fransen, fcn. CF125. MALAYSIA: 1 male pocl. 2.4 mm (rmnh.crus.d.53797; GenBank OQ603095 (coi)), stn sem.20, Sabah, Semporna area, Creach Reef, 04°18’58.8”N 118°36’17.3”E, 5.xii.2010, depth 5 m, scuba diving, in P. penguin on Antipathes, coll. C.H.J.M. Fransen. – 1 non ovigerous female pocl. 2.7 mm (rmnh.crus.d.53867), stn sem.15, Sabah, Semporna area, Ligitan Isl., Ligitan 3, 04°12’43.0”N 118°54’36.6”E, 3.xii.2010, depth 15 m, scuba diving, in P. penguin (Ø 20 cm), coll. C.H.J.M. Fransen. – 1 juvenile pocl. 1.1 mm (rmnh.crus.d.53872), stn sem.15, Sabah, Semporna area, Ligitan Isl., Ligitan 3, 04°12’43.0”N 118°54’36.6”E, 3.xii.2010, depth 15 m, scuba diving, in P. penguin (Ø 6 cm), coll. C.H.J.M. Fransen. – 1 male pocl. 3.0 mm (red dots) (rmnh.crus.d.53787; GenBank OQ603094 (coi) & OQ600402 (16S)), stn sem.36, Sabah, Semporna area, N Gaya Island (back), 04°37’57.6”N 118°45’32.3”E, 10.xii.2010, depth 10 m, in ? Spondylus sp. with even valves, not attached, rim brown-white, gills orange, coll. C.H.J.M. Fransen. – 1 male pocl. 1.8 mm (rmnh.crus.d.53926; GenBank OQ603096 (coi)), stn sem.51, Sabah, Semporna area, Tabawan Isl., 04°47’15.6N” 118°25’00.8”E, 16.xii.2010, depth 18 m, scuba diving, in P. penguin on Antipathes, coll. C.H.J.M. Fransen. PHILIPPINES: 1 male pocl. 3.0 mm, 1 ovigerous female pocl. 4.1 mm (rmnh.crus.d.48386), stn ceb.21, Cebu Strait, SW of Bohol, S of Panglao, NE side of Balicasag Island, ‘black forest’, 9°30.97’N 123°41.34’E, 20.xi.1999, depth 30 m, scuba diving, large octocorals on sand, in Pteria sp. (Ø 20 cm) on Antipatharia, coll. C.H.J.M. Fransen. – 1 ovigerous female pocl. 4.6 mm (rmnh.crus.d.48385), stn ceb.21, Cebu Strait, SW of Bohol, S of Panglao, NE side of Balicasag Island, ‘black forest’, 9°30.97’N 123°41.34’E, 20.xi.1999, depth 30 m, scuba. diving, large octocorals on sand, in Pteria sp. on Antipatharia, coll. C.H.J.M. Fransen. – 1 male pocl. 2.7 mm, 1 ovigerous female pocl. 3.6 mm (rmnh.crus.d.48384), stn ceb.09, Cebu Strait, W of Bohol, N side of Cabilao Island, NE of Looc, 9°53.59’N 123°46.92’E, 12.xi.1999, depth 20 m, scuba divng, overhanging wall with caves, in P. penguin on Antipatharia, coll. J. Goud. – 1 male pocl. 1.8 mm (rmnh.crus.d.48383), stn ceb.08, Cebu Strait, W of Bohol, S side of Cabilao Island, Cabacungan Point, 9°51.55’N 123°45.95’E, 11.xi.1999, depth 25 m, overhanging wall with caves, in Lopha cristagalli (L.) on Antipatharia, coll. C.H.J.M. Fransen. – 1 male pocl. 2.9 mm (rmnh.crus.d.48382), stn ceb.05, Cebu Strait, W of Bohol, W side of Cabilao Island, S side fish sanctuary, 9°52.60’N 123°45.61’E, 8.xi.1999, depth 25 m, scuba diving, vertical wall with caves, in large Pteria sp. on Antipatharia, coll. C.H.J.M. Fransen.

Diagnosis. Rostrum well developed, laterally compressed in distal part, straight, almost reaching end of second segment of antennular peduncle, with 5–7 dorsal distal teeth and 0-1 ventral distal tooth; row of setae between dorsal teeth. Carapace with antennal spine well developed; articulating hepatic spine present, situated in depression somewhat posteroventrally of antennal spine; inferior orbital angle slightly produced; anterolaterlal angle rounded, slightly produced. Telson with two pairs of small dorsal spines at about 0.6 and 0.8 of telson length. Basal segment of antennular peduncle with distolateral tooth; outer flagellum with basal four segments fused, free shorter ramus of two or three segments. Scaphocerite well developed with almost straight lateral margin; distolateral tooth normal, reaching distal margin of lamina, sometimes just overreaching distal margin of lamina; slit between distolateral tooth and lamina shallow. First pereiopod slender, chela sub-spatulate, minutely pectinate in distal two-thirds of lateral margin. Second pereiopods subequal in shape and size; dactylus just overreaching fixed finger, with one large triangular tooth in proximal half, densely setose on lateral margin; fixed finger with 4–7 small teeth in proximal half. Ambulatory pereiopods with biunguiculate dactyli; slender accessory tooth, covered with minute scale-like spinules; unguis dorsally flattened, with dense cover of minute scale-like spinules. Uropods with protopodite with strong acute lateral tooth; lateral margin of exopod convex with small mobile spine distolaterally.

As Polkamenes nobilii except for the accessory tooth on the dactyli of the ambulatory pereiopods, which is without minute spinulation.

Remarks. Since Polkamenes nobilii appears to have the chela of the first pereiopods with pectinate cutting edges, the differences between P. pycnodontae and P. nobilii are smaller than previously thought. Both species have many setae on the dactylus of the second pereiopods. The only remaining difference is the absence of a minute spinulation in the accessory tooth of the ambulatory pereiopods of P. pycnodontae while in P. nobilii this is usually present although sometimes indistinct. As no other differences have been found, P. pycnodontae may prove to be a synonym of P. nobilii.

Differences with Polkamenes spondylis are minor. In P. spondylis the accessory tooth on the dactylus of the ambulatory pereiopods seems stouter than in the type-species of P. pycnodontae. Although not mentioned in the description, Fig. 8a of Suzuki (1971) shows a minute spinulation on the accessory tooth of the ambulatory dactyli. Of both species, only the holotypes are known. Additional material could provide information on their intraspecific variation, elucidating their relationship. The holotype of P. spondylis should be checked for lateral cutting edges of the chela of the first pereiopods being pectinate and sub-spatulate or not. As in P. nobilii, this character could be overlooked in P. spondylis.

Colour. “Semi-transparent with numerous small round evenly distributed red chromatophores, all over body, ambulatory pereiopods, antennae and caudal fan. Similar but slightly larger chromatophores over second pereiopods. Chromatophores absent from antennal flagella and propods of ambulatory pereiopods.” (Bruce, 1978c: 238).

Hosts. Recorded from Grypheidae: Hyotissa hyotis (L., 1758) (Bruce, 1978c, 1980 as Pycnodonta hyotis; De Grave, 1999); Hyotissa sp. together with a species of the fish genus Onuxodon Smith, 1955 (Carapidae) (Bruce, 1981c; Bruce, 1983b). From Pteriidae: Pteria penguin (Röding, 1798) (De Grave, 1999, as ‘Magnavicula penguin’). From Margaritidae: Pinctada margaritifera (L., 1758) (Poupin, 1998; Li, 2008b). Now newly recorded from: Lopha cristagalli (L., 1758) (Ostreidae), Vulsella vulsella (L., 1758) (Vulsellidae), and an unknown species of Spondylus L., 1758 (Spondylidae).

Distribution. Heron Island, Queensland, Australia (cf. Bruce, 1978c, 1980, 1981c); Lizard Island, Australia (Horká et al., 2016); Taiwan (Chow et al., 2021); Ambon, Indonesia (Fransen, 1994a); Tuamotu Islands, French Polynesia (Poupin, 1998; Li, 2008b). Now for the first time recorded from the following localities in Indonesia: E of Komodo, Bali, Teluk Dodinga (off Halmahera mainland), NE Sulawesi, Seribu (Thousand Islands), NE Kalimantan, West Papua. Also newly recorded from Sabah, Malaysia; and Cebu, Philippines.

Polkamenes spondylis (Suzuki, 1971)

Paranchistus spondylis Suzuki, 1971: 15–19, figs. 8, 9 [type locality: Shiraiso, near the Manazuru M.B.L.]; Bruce, 1972a: 221 (listed); Bruce, 1975a: 162 (listed); Müller, 1993: 52 (listed); Fransen, 1994a: 111 (listed); Li, 2000: 113, fig. 124 (listed); Bruce, 2003b: 223 (listed); Li et al., 2004: 538, fig. 24; Hayashi, 2005: 516, figs. 511, 512; Hayashi, 2006: 510; Li et al., 2007: 247, fig. 120 (listed); De Grave & Fransen, 2011: 357 (listed).

Paranchistus spondylus – Müller, 1993: 52 [erroneous spelling].

Diagnosis. Rostrum well developed, laterally compressed in distal part, straight, almost reaching end of second segment of antennular peduncle, with four dorsal distal teeth and 0–1 ventral distal tooth; row of setae between dorsal teeth. Carapace with antennal spine well developed; articulating hepatic spine present, situated in depression somewhat posteroventrally of antennal spine; inferior orbital angle slightly produced; anterolateral angle rounded, slightly produced. Telson with two pairs of small dorsal spines at about 0.6 and 0.8 of telson length. Basal segment of antennular peduncle with distolateral tooth; outer flagellum with basal three segments fused, free shorter ramus of four segments. Scaphocerite well developed with slightly convex lateral margin; distolateral tooth normal, reaching distal margin of lamina, slit between distolateral tooth and lamina shallow. First pereiopod slender, chela sub-spatulate, cutting edges entire. Second pereiopods subequal in shape and size; dactylus as long as fixed finger, with one large triangular tooth in proximal half, densely setose on lateral margin; fixed finger with 4–6 small teeth in proximal half. Ambulatory pereiopods with biunguiculate dactyli; slender accessory tooth, with minute scale-like spinules; unguis dorsally not flattened, with dense cover of minute scale-like spinules. Uropods with protopodite with strong acute lateral tooth; lateral margin of exopod convex with small mobile spine distolaterally.

Remarks. Like in Polkamenes liui, the cutting edge of the chela of the first pereiopods is without minute denticulation according the author (Suzuki, 1971). As the other species in the ‘Anchistus clade’ do possess the minute denticulation on the cutting edges of the first pereiopod chelae, this is a reversion to the plesiomorphic state. As only the holotype and two juveniles (Li et al., 2004) are known, more material will be needed to check if this character really is typical for the species. Although not reported in the description of the species, Suzuki (1971, Fig. 8a) figures the accessory tooth of the ambulatory dactyli with small spinules.

Colour. “The body is translucent. Many small reddish spots can be seen on the body and thoracic appendages as shown in text-fig. 8 in dotting.” (Suzuki, 1971: 18). The specimen from Semporna also had red dots.

Hosts. Recorded from Spondylidae: Spondylus squamosus Schreibers, 1793 (Suzuki, 1971; Hayashi, 2005, 2006; as Spondylus barbatus Reeve, 1856). Also from Vulsellidae: Vulsella vulsella (L., 1758) (Li et al., 2004; Hayashi, 2006).

Distribution. Shiraiso, Manazura-Machi, Kanagawa Prefecture, Japan, (cf. Suzuki, 1971, Hayashi, 2005, 2006); South China Sea (Li et al., 2004).

Genus Tympanicheles gen. nov.

ZooBank: urn:lsid:zoobank.org:act:5020D378-966A-4801-BD63-C26BA625E675

Diagnosis. Small to moderately sized shrimps of subcylindrical body form. Rostrum well developed, compressed, with teeth in distal part, lateral carinae feebly developed. Carapace smooth, glabrous; orbit feebly developed, inferior orbital angle distinct, antennal spine present, supraorbital and epigastric spines absent, hepatic spine absent or present, if present mobile, anterolateral margin not or feebly produced. Abdomen smooth, glabrous, third segment not posterodorsally produced, anterior pleura rounded, posterior blunt. Telson with two pairs of dorsal spines in distal half, three pairs of posterior spines. Eye small, cornea globular. Antennula normal, proximal segment of peduncle with distolateral tooth, upper flagellum biramous, flagella short, short ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp, laciniae broad; maxilla with simple palp, basal endite broad, bilobed, coxal endite obsolete, scaphognathite broad; first maxilliped with slender palp, basal endite broad, fused with coxal endite, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod bilobed; second maxilliped with normal endopod, flagellum with numerous plumose setae distally, epipod subrectangular, without podobranch; third maxilliped with endopod slender, ischiomerus distinct from basis, exopod with numerous plumose setae distally, coxa with oval lateral plate, with rudimentary arthrobranch. Fourth thoracic sternite without median process. First pereiopods chelae with fingers sub-spatulate, cutting edges or minutely pectinate. Second pereiopods well developed, similar, unequal, dactylus with large acute triangular tooth in proximal half, fixed finger with series of teeth in proximal part; palm with oblong ventral oval tympanal organ over entire length. Ambulatory pereiopods with dactyli simple, corpus without distinct accessory tooth, with carina with small denticle(s) on flexor margin, with dorsodistal transverse wrinckles; without basal protuberance; unguis not flattened, with fine scale-like spinules dorsally. Uropod with protopodite posterolaterally acute, exopod with small mobile distolateral spine.

Etymology. ‘Tympanicheles’: named after the ‘drum-like’ veil on the species’ major chela. Built from ‘Tympani-’, a suffix for drum in Latin (‘Tympanum’), and ‘-cheles’ for claws in Latin. Gender: masculine.

Type species by present designation: Paranchistus ornatus Holthuis, 1952 (= Tympanicheles ornatus (Holthuis, 1952)).

We tentatively recognize two species: Tympanicheles ornatus (Holthuis, 1952), and Tympanicheles pectinis (Kemp, 1925).

Key to the species of Tympanicheles

1. 1.Movable hepatic spine present; rostrum with series of 4–6 subdistal and distal teeth; ambulatory pereiopod dactyli oblong, with unguis slightly curved...................................................................T. ornatus
2. –Hepatic spine absent; rostrum with 3 distal teeth; ambulatory pereiopod dactyli short, compact, with unguis strongly hookedT. pectinis

Tympanicheles ornatus (Holthuis, 1952)

(figs. 36A–B, 37, 39A,C)

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A, B) Tympanicheles ornatus (Holthuis, 1952), rmnh.crus.d.42794, from Atrina vexillum (Born, 1778); C, D) Tympanicheles pectinis (Kemp, 1925), rmnh.crus.d.58094, Vanuatu, stn LD25, host unknown.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

photos by c.h.j.m fransen (a, b) and tin-yam chan (c, d)

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Tympanicheles ornatus (Holthuis, 1952). A-C, F-H) rmnh.crus.d.41497, ovigerous female, pocl. 6.4 mm; D) rmnh.crus.d.41491, ovigerous female, pocl. 8.7 mm; E) idem, pocl. 8.8 mm. A) habitus, lateral view; B) anterior appendagees, dorsal view; C) anterior appendages, lateral view; D, E) rostrum, lateral view; F) telson, dorsal view; G) right second pereiopod chela, medial view; H)right third pereiopod dactylus, medial view. Scale A = 4 mm; B, C = 2 mm; D, E, G = 1 mm; H = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Paranchistus ornatus Holthuis, 1952: 97–100, figs. 39, 40 [type locality: Mozambique]; Barnard, 1955 (listed): 5; Barnard, 1958 (listed): 12; Rosewater, 1961: 195; Jacquotte, 1963: 61; Hipeau-Jacquotte, 1967: 153–166; Hipeau-Jacquotte, 1971: 194, figs. 4, 5 9; Bruce, 1972a: 219–221, colour figures (listed); Hipeau-Jacquotte, 1972a: 288, fig. 2a2; Hipeau-Jacquotte, 1972b: 10, 14, 17, figs. 1a2–e2, 3a2, 3b2, 4a2–d2, 6b, 7a2–f2, 8a2–d2; Thomassin, 1972: 311; Hipeau-Jacquotte, 1973a; 96–116, fig. 1a2–e2, 3a2–b2, 4a2–d2, 5, 6b, 7a2–f2, 8a2–d2; Hipaeu-Jacquotte, 1973b: 63–70; Hipeau-Jacquotte, 1974a: 367–382; Hipeau-Jacquotte, 1974b: 383–402; Hipeau-Jacquotte, 1974c: 403–407; Hipeau-Jacquotte, 1974d: 359–386; Thomassin, 1974: 306; Bruce, 1975a: 162 (listed); Bruce, 1976a: 93; Bruce, 1976d: 471: Monod, 1976a: 839 (listed); Bruce, 1978a: 119; Bruce, 1978b: 279; Bruce, 1980: 179, textfig. 1a, pl. 1 figs. a–c; Müller, 1993: 51 (listed); Fransen, 1994a: 107, 111, 112, fig. 2g, pl. 2 fig. 3; Fransen, 1994b: 117, fig. 2g, pl. 2D; Li, 2000: 111, fig. 121 (listed); De Grave & Fransen, 2011: 357 (listed); Chow et al., 2021: table A.1 (listed).

Material examined. RED SEA: 3 males pocl. 3.90, 4.22, 4.74 mm, 7 ovigerous females pocl. 7.40, 7.92, 8.18, 8.18, 8.31, 8.70, 8.83 mm (rmnh.crus.d.41491), Nocra Island, 18.iii.1962, Israel Red Sea Expedition no. E62/2028. – 1 ovigerous female pocl. 6.10 mm (rmnh.crus.d.41492), Loe Salina, 1965, in Atrina sp., Israel Red Sea Expedition no. E65/1868. – 3 males pocl. 3.64, 3.90, 4.42 mm, 3 ovigerous females pocl. 7.53, 7.66, 8.70 mm (rmnh.crus.d.41493), off Nocra Island, 17.iii.1962, in Atrina sp., Israel Red Sea Expedition no. E62/1350. – 1 male pocl. 5.32 mm, 1 ovigerous female pocl. 9.09 mm (rmnh.crus.d.41494), ne of Nocra Island, 18.ii.1962, depth 2-3 m, in Atrina sp. (10049), Israel Red Sea Expedition no. E62/1354. – 3 males pocl. 4.35, 4.87, 4.94 mm (rmnh.crus.d.41495), Nocra Island, 18.iii.1962, Israel Red Sea Expedition no. E62/2059. – 1 male pocl. 4.48 mm (rmnh.crus.d.41496), Umm Aabak, 4.v.1962, Israel Red Sea Expedition no. 1452. – 2 males pocl. 3.05, 3.57 mm, 1 female pocl. 5.52 mm, 1 ovigerous female pocl. 6.36 mm (rmnh.crus.d.41497), sw of Umm Aabak, near Nocra Island, 22.iii.1962, depth 0-3 m, in Atrina sp., Israel Red Sea Expedition no. E62/1379. MOZAMBIQUE: 1 male holotype pocl. 5.97 mm (zma.crus.D.102827), published by Holthuis, 1952: 97–100, figs. 39, 40. SEYCHELLES: 1 ovigerous female pocl. 7.7 mm (rmnh.crus.d.42794), niop-E stn sey.748, E of Mahé, E coast of Sainte Anne Island, 4°37’S 55°31’E, 25.xii.1992, depth 10 m; scuba diving, in Atrina vexillum (Born), coll. C.H.J.M. Fransen.

Diagnosis. Rostrum well developed, laterally compressed towards distal part, bent downwards, reaching end of te second segment of antennular peduncle, with 3–5 dorsal distal teeth, without ventral distal teeth; row of setae between dorsal teeth. Carapace with well-developed antenna tooth, with small articulating hepatic spine, situated somewhat posteroventrally of antennal spine; inferior orbital angle acute, slightly produced; anterolateral angle broadly rounded, slightly produced. Sixth abdominal segment with posterior ventral margin rounded. Telson with two pairs of small dorsal spines at 0.58 and 0.81 of telson length; lateral pair of terminal spines placed just behind intermediate pair. Basal segment of antennular peduncle with one (seldom two) distal teeth, anterior margin almost straight; outer flagellum with basal 4–6 segments fused, free shorter ramus of two or three segments. Scaphocerite well developed with slightly convex lateral margin; distolateral tooth normal, almost reaching the distal margin of the lamina; slit between distolateral tooth and lamina shallow. First pereiopod slender, chela sub-spatulate, minutely pectinate in distal two-third of lateral margin. Second pereiopods usually equal in size and shape in females, subequal in size in males; dactylus with one large tooth in proximal half; fixed finger with 5–6 small teeth in proximal half; palm with oblong ventral oval tympanal organ over entire length. Ambulatory pereiopods with slender long slightly curved non-biunguiculate dactyli; serrated carinae on distoventral margin of corpus; unguis not flattened, dorsally and ventrally with transverse rows of scale-lake spinules. Uropod with protopodite posterolaterally acute, exopod with small mobile distolateral spine.

Remarks. Smaller specimens have the dorsal rostral teeth in the distal fourth of the rostrum while larger specimens have them all at the tip. This indicates that the dorsal rostral teeth are placed more distally after each moult as has been observed in Anchistus australis.

Colour (figs. 36A,B). “Uniformly covered all over body and appendages with small red chromatophores, with minute yellow and white chromatophores interspersed.” (Bruce, 1978a: 119; see colour figures Bruce, 1972a).

Hosts. Reported from Pinnidae: Atrina vexillum (Born, 1778) (Hipeau-Jacquotte, 1967, 1973b, 1974b; Bruce, 1976e, 1978a, 1978b, 1980; Fransen, 1994b); Pinna bicolor Gmelin, 1791 (Rosewater, 1961; Hipeau-Jacquotte, 1967).

Distribution. Distributed along the East African coast: Mocambique (Holthuis, 1952); Zanzibar and Kenya (cf. Rosewater, 1961; Bruce, 1976d, 1980), Madagascar (cf. Hipeau-Jacquotte, 1967, 1971, 1972a, 1972b, 1973a, 1973b, 1974a, 1974b, 1974c, 1974d; Thomassin, 1972, 1974; Bruce, 1978b), Comoro Islands (cf. Bruce, 1978a); Seychelles (Fransen, 1994b); Nocra Island, Red Sea (Fransen, 1994a).

Tympanicheles pectinis (Kemp, 1925)

(figs. 36C,D, 38)

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Tympanicheles pectinis (Kemp, 1925), rmnh.crus.d.26972, male, pocl. 3.9 mm. A) habitus, lateral view; B) anterior appendages, dorsal view; C) idem, lateral view; D) rostrum, lateral view; E) telson, dorsal view; F) left first pereiopod chela, lateral view; G) right second pereiopod, ventral view; H) idem, chela, medial view; I) right third pereiopod dactylus, lateral view. Scale A, G = 4 mm; B, C = 2 mm; D-F, H = 1 mm; I = 0.1 mm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

artwork by c.h.j.m. fransen

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Anchistus pectinis Kemp, 1925: 327–330, figs. 19, 20 [Type locality: Octavia Bay, Nancowry Harbor, Nicobars]; Holthuis, 1952: 13 (listed); Bruce, 1967: 568; Fujino & Miyake, 1967: 293-296, figs. 1–3; Suzuki, 1971: 101–106, figs. 5–7, pl. 2; Bruce, 1972a: 219 (listed); Bruce, 1975a: 150, 162 (listed); Bruce, 1976d: 465; Bruce, 1977b: 175–176, fig. 6e; Bruce, 1983c: 200 (listed); Bruce, 1990: 15, 18 (listed); Bruce, 1991a: 261, 275, fig. 24; Bruce, 1991b: 378–381, figs. 56–57, 71 d-f; Müller, 1993: 11 (listed); Fransen, 1994a: 107, 111, fig. 2b; Bruce, 1996: 205, figs. 2, 3; Li, 2000: 12, fig. 12 (listed); Yamaguchi & Holthuis, 2001: 107, 109, 135, fig.; Hayashi, 2002: 224, figs. 432k, l, 434i, j, 435i, j; Hayashi, 2006: 510, 512; De Grave & Fransen, 2011: 340 (listed); Radhakrishnan et al., 2012: table 1 (listed); Samuel et al., 2016: table 1 (listed).

Anchistus misakensis Yokoya, 1936: 136, fig. 5 [Type locality: Octavia Bay, Nancowry Harbor, Nicobars]; Holthuis, 1952: 13; Bruce, 1967: 568 (key).

Material examined. JAPAN: 1 ovigerous female pocl. 3.51 mm, 1 male pocl. 3.90 mm (rmnh.crus.d.26972), Kanagawa prefecture, Sagami Bay near Manazuru, S of Odawara, 25.viii.1968, coll. H. Suzuki. INDONESIA: 1 non ovigerous female pocl. 1.8 mm (rmnh.crus.d.47465), stn mal.21, Moluccas, Ambon, Ambon bay, N coast Cape Hatupero, E of Lilibooi, 03°44’S 128°02’E, 20.xi.1996, depth 10 m, scuba diving, in pectinid shell, coll. C.H.J.M. Fransen. VANUATU: 1 non ovigerous female pocl. 1.6 mm (rmnh.crus.d.58094), stn ld25, N Aoré, 15°19’29”S 167°06’19”E, 7.x.2006, scuba diving, depth unknown.

Diagnosis. Rostrum well developed, laterally compressed towards distal part, bent downwards; reaching just beyond basal segment of antennular peduncle, with 3, seldom 2 distal teeth with setae in between. Antennal spine present, hepatic spine absent; inferior orbital angle slightly produced; anterolateral angle rounded, not produced. Sixth abdominal segment with posterior ventral margin rounded. Telson with dorsal pairs of spines at 0.61 and 0.79 of telson length; lateral pair of terminal spines placed just behind intermediate pair. Basal segment of antennular peduncle with one small distolateral tooth. Scaphocerite with lateral margin almost straight, slit between distolateral tooth and lamina of moderate depth. Chela of first pereiopods spatulate, with minutely pectinate cutting edges distolaterally. Second pereiopods unequal; dactylus exceeding fixed finger, distally strongly hooked, with one large triangular tooth in proximal half, fixed finger with 4-6 small teeth in proximal half of which distalmost largest; palm with oblong oval tympanal organ on entire medio-ventral surface. Ambulatory dactyli simple; corpus with carinated ventral margin with small triangular subdistal denticle, distodorsally transversely wrinckled; unguis strongly hooked, not flattened, with transverse rows of minute scale-like spinules dorsally. Uropod with protopodite posterolaterally acute, exopod with small mobile distolateral spine.

Remarks. The variability in the development of the accessory tooth on the dactylus of the ambulatory pereiopods ranging from its absence in Kemp’s material to well developed in the type of Anchistus misakiensis Yokoya, 1936 and the illustrated specimen from New Caledonia (indicated as Lagon, stn. cc 147) of Bruce (1991b) attributes to the opinion that A. misakiensis is conspecific with Tympanicheles pectinis. In the two specimens studied the accessory tooth was absent or minute (fig. 38I). Differences in the male first endopod as noted by Bruce (1991b: 381) could be due to different developmental stages involved. In the present male (pocl. 3.90 mm) 13 spinules are present on the proximal median margin. In the male specimen (pocl. 2.7 mm) from New Caledonia (Bruce, 1991b: fig. 56k) only six spinules are present while in a large male specimen (pocl. between 3.65 and 5.88 mm) from Japan (Suzuki, 1971: fig. 7.4) at least 10 spinules are present.

Colour (figs. 36C, D). “The body is translucent. A number of reddish circular marking, which are encircled with purplish colouration, are found on the body and appendages; these marks are variable in size and number. The distal portion of the antennular and antennal peduncles, the scaphocerite, the second chela, the telson and the uropod is purplish in colour.” (Suzuki, 1971: 13, textfig. 5, pl. 2).

Hosts. Reported from Pectinidae: Bractechlamys vexillum (Reeve, 1853) (Bruce, 1996, as Semipallium vexillum (Reeve, 1853)); Mimachlamys crassicostata (G. B. Sowerby ii, 1842) (Hayashi, 2002, 2006, as Mimachlamys nobilis (Reeve, 1852); Pecten albicans (Schröter, 1802) (Fujino & Miyake, 1967; Suzuki, 1971; Hayashi, 2002, 2006, as P. (Notovola) albicans); Pecten sp. (Kemp, 1925); Yilistrum balloti (Bernardi, 1861) (Yokoya, 1936; Suzuki, 1971; Bruce, 1977b, 1983b, 1991a, 1991b, 1996; Hayashi, 2002, 2006, as Amusium ‘japonicum’ balloti (Bernardi, 1861)); Pectinid bivalve (Bruce, 1976d). Also one record from an unidentified bivalve (Bruce, 1977b).

Distribution. Nicobar Islands (Kemp, 1925); Zanzibar (Bruce, 1976d); Japan (Yokoya, 1936; Fujino & Miyake, 1967; Suzuki, 1971; Hayashi, 2002, 2006); Townsville, Australia (Bruce, 1977b), Keppel Bay and Magnetic Island, Australia (Bruce, 1983b); New Caledonia (Bruce, 1991a, 1991b, 1996). Now newly recorded from Ambon, Indonesia, and Vanuatu.

Key to the genera of the ‘Anchistus’ clade

1. 1.Unguis of ambulatory pereiopods with few scattered minute scales dorsally......2
2. –Unguis of ambulatory pereiopods with dense cover of minute scales dorsally...4
3. 2.Ambulatory dactyli without obtuse compressed ventral process..............................3
4. –Ambulatory dactyli with obtuse compressed ventral process..................Dasella
5. 3.Ambulatory pereiopods biunguiculate; mobile hepatic spine present......................................................................Paranchistus
6. –Ambulatory pereiopods simple; hepatic spine absent.......................................Ensiger
7. 4.Rostrum laterally compressed, distally acute, with teeth in distal part.................5
8. –Rostrum broad, swollen, distally truncate, without teeth...............Neoanchistus
9. 5.Palm of second chelipeds with tympanal organ...............................................................6
10. –Palm of second chelipeds without ventral tympanal organ; mobile hepatic spine present...........Polkamenes gen. nov.
11. 6.Tympanal organ on palm of second cheliped oblong; dorso-distal part of corpus of ambulatory dactyli wrinkled...............................Tympanicheles gen. nov.
12. –Tympanal organ on palm of second cheliped restricted to proximal part of palm; dorso-distal part of corpus of ambulatory dactyli glabrous.....Anchistus

Discussion

Phylogenetical significance of morphological features

Comparing phylogenetic trees resulting from the concatenated molecular alignment and the morphological character state dataset could give us an insight in which morphological characters are more phylogenetically significant than others. Previous authors have made some remarks on the subject, which will be discussed below, together with new findings.

Bruce (1975b, 1976a) mentioned that the “irrelevant” colour patterns of Anchistus (s.l.) have little specific relevance due to the shrimps endosymbiotic lifestyle and their monogamous mating system (Neo et al., 2015). This implies that the conspicuous colourations have no obvious advantages or disadvantages (Bruce, 1976a). Consequently, there would be no strong selection pressure for this character. The whole ingroup clade can be seen exhibiting a spotted (or polka-dotted) colour pattern (figs. 4, 17, 20, 33, 36; Bruce, 1972a), with the exception of Neoanchistus (fig. 28; A. Anker, pers. comm.), and to some extent A. pectinis. The colour pattern of Neoanchistus and A. pectinis somewhat resembles that of other endosymbiotic shrimps, such as those of the genus Platypontonia Bruce, 1968 (see de Gier et al., 2022). Why these species exhibit a distinct pattern of larger red spots is unknown, but this may be concordant with the species’ aberrant host choice, consisting of pectinid and cardiid bivalves. All other ingroup species appear to have a similar spotted pattern, although two groups can be distinguished by their spots and colouration (Bruce, 1972a; supplementary appendix S1, supplementary table S2). Minute white, red or yellow spots can be found in Dasella, Tympanicheles ornatus and both species of Ensiger. In addition, minute spots can also be found in the more closely related outgroups, like Zenopontonia, Lipkemenes and Periclimenes kempi, confirming the basal placement of some of the before-mentioned species. Larger spots, usually a combination of both blue and red (or orange) chromatophores, can be found in all other ingroup species: Anchistus australis, A. demani, A. miersi, Polkamenes pycnodontae, P. spondylis, and additionally to some extent in Tympanicheles ornatus. The colour pattern of T. ornatus resembles the minute spots of E. custoides (figs. 20, 36), although closer inspection (e.g., mnhn-iu-2010-4971) reveals that the yellow spots are larger and that additional orange spots are present. Projection of the colour patterns on the molecular trees show that larger spots are derived characters and that they are only found in symbionts of larger bivalves.

The presence of minutely pectinate cutting edges of spatulate to subspatulate first chelipeds is considered to be a definitive character for the studied ingroup genera (e.g., Bruce, 1995; Fransen & Van der Meij, 2010), but was also found in the related outgroup species Lipkemenes, Zenopontonia, Actinimenes and both Periclimenes colemani and P. kempi (supplementary appendix S1, supplementary table S2). A quick investigation also proves that Sandimenes and various members of Periclimenes and Allopontonia (which were proven to be somewhat related to the currently studied ingroup by Chow et al., 2021) also have subspatulate first chelipeds, although the associated minutely pectinate cutting edges cannot be seen in the published illustrations (Bruce, 1971, 1972b, 1995, 2010b; Li, 2009; Rauch et al., 2019), except for the illustrations of P. josephi, which show “a distal row of pectinate short setae” (Li, 2008b). Closer examination of collection material is needed in order to see if minutely pectinate cutting edges are also present in related ectosymbiotic species. The potential function of the (sub)spatulate cheliped shape is currently unknown, although it may be linked to the dietary habits of the shrimp. Species could be using the minor chelipeds to harvest and digest their hosts’ mucus and ‘steal’ food particles, such as in E. custos (Johnson & Liang, 1966), although the cheliped morphology of E. custos and E. custoides is quite aberrant (e.g., fig. 27A). Interestingly, De Grave et al. (2021) concluded that representatives of the currently studied clade, Actinimenes ornatus, Zenopontonia soror, and Anchistus miersi, were facultative or obligate parasites, feeding from the hosts’ tissue. Comparatively, the limited information on the bivalve-associated species from the other endosymbiotic palaemonid clade (de Gier et al., 2022) were found to feed from host mucus strands and/or pseudofeces (Kennedy et al., 2001; Ashelby et al., 2015). In addition, Pontonia pinnophylax (Otto, 1821) was found to be feeding from similar carbon sources as its host (De Grave et al., 2021), making it a ‘true’ commensal symbiont.

The flat oval-shaped ‘tympanal’ organ found on the underside of the second chelipeds was first described and figured by Monod (1976a) for Anchistus miersi. This structure can be found in various members of the ingroup: Anchistus australis, A. demani, A. miersi, and A. gravieri bear major claws with small, distinct tympanal organs (fig. 39B, D–F), while both species of Tympanicheles, Neoanchistus nasalis, and possibly N. cardiodytes, bear major claws with larger, less-pronounced tympanal organs (fig. 39A, C). In A. australis, the ‘veil’ is much thinner than the surrounding rim and the rest of the claw (fig. 39E, F). Although the systematic position of T. pectinis, A. gravieri, and Neoanchistus cannot be confirmed with the current molecular data, T. ornatus has a more basal placement than A. australis, A. demani, and A. miersi (fig. 1). Thus, it seems that a dinstinctly outlined smaller organ evolved from a less clearly delimited larger organ. More morphological and histological work is needed in order to see if the surface of the tympanal organ is homologous to the outer surface of the chelae of other species in the ingroup. The potential function of the organ is unknown, and a potential link to the host choice could also not be found (with T. ornatus occupying the same hosts as Ensiger). Similar drum-looking organs are used for interspecies communication, host detection, or predator avoidance in various groups of insects (described as a ‘tympanum’: Yack, 2004; Strauß & Lakes-Harlan, 2014) and as a ‘directional air motion sensor’ in the spider genus Hortipes Bosselaers & Ledoux, 1998 (Ramírez, 2014). Perhaps the functionality of the drum-like organ for shrimps can be found in the field of bioacoustics (e.g., Lovell et al., 2005). In crustaceans, similarly looking structures called ‘gas windows’ or also ‘tympana’ can be seen in the last walking leg pairs and sometimes thoracic sternites of semi-terrestrial sand bubbler crabs (Brachyura: Dotillidae), which they use for osmoregulation (Matsumasa et al., 2001). In various other semi-terrestrial crabs, small ‘window-like’ organs called ‘Barth’s myochordotonal organs’ can be found, which play a role in intraspecific communication, being able to respond to vibrations transmitted through the exoskeleton from the substrate and the air (Davie et al., 2015). In male Australian freshwater crayfish Cherax quadricarinatus (von Martens, 1868), sexually dimorphic ‘red patches’ on the propodus of the major claws’ can be found. The function of this uncalcified structure was reviewed by Karplus et al. (2003) and hypothesized to be a sensory organ, possibly used in intraspecific social interactions. Various species of amphipods within the Bogidiellidae, Niphargidae, and Ingolfiellidae exhibit ‘windows’ in the cuticle of the pereiopods, pleon, and pereion, called ‘lentiform organs’ (Pretus & Stock, 1990). As for now, the function of these structures remains unknown (Vonk & Schram, 2003). In addition, a semi-transparent structure can be found on the dorsal sides of the heads of ‘mountain shrimp’ (Anaspidacea) in the genus Allanaspides Swain, Wilson, Hickman & Ong, 1970, which resembles the structures found in amphipods, mentioned above (Vonk & Schram, 2003).

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Tympanal organ on the second chelipeds of various ingroup members, and the veil figured in detail for every claw. sem captures: A (C detail), Tympanicheles ornatus (Holthuis, 1952) (rmnh.crus.d.41491); B (D detail), Anchistus miersi (De Man, 1888) (rmnh.crus.d.58030). µCT model: E (F detail; rotated), Anchistus australis Bruce, 1977 (rmnh.crus.d.53540). White arrows indicate proximal and distal border of tympanal organ. Scale bars: A: 1 mm; B-F: 500 µm.

Citation: Contributions to Zoology 92, 3 (2023) ; 10.1163/18759866-bja10042

photographs by p. helleman, j. van den oever (a–d), & w. de gier (e–f)

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The walking legs’ (third to fifth pair of pereiopods’) dactyli bear many of the characteristic features used for species and genera identifications within the present shrimp clade (Fransen, 2002). In most cases, the dactyli are well-illustrated in taxonomic literature, revealing the wide range of morphological ornamentations and setation patterns on the corpus and unguis. Although homology and sequential evolution in the structures are sometimes hard to dinstinguish (supplementary appendix S1; supplementary table S2), some characters give the impression to be unique to bivalve- and ascidian-associated endosymbiotic shrimp (Fransen, 1994a, 2002; de Gier & Fransen, 2018; de Gier et al., 2022). However, Chow et al. (2021) showed that the overall shape of a ‘biunguiculate’ dactylus has evolved many times in both endo- and ectosymbionts, and bears no phylogenetic signal on a higher taxonomic level. Similarly, in the present clade, traces of convergent evolution can be found in the accessory teeth on the flexor margin of the dactylar corpus: all species of Dasella show a blunt, distoventral process (fig. 19D), while Paranchistus armatus has a somewhat sharper tooth (fig. 30J; almost resembling species of Pontonia and Odontonia (Fransen, 2002; de Gier & Fransen, 2018). In addition, both species of Ensiger have no accessory teeth whatsoever (figs. 22E, 27D). Higher up in the tree (see fig. 1), Polkamenes pycnodontae (as well as P. spondylis and P. nobilii) exhibit a strong accessory tooth (figs. 34K, L, 35S), while Tympanicheles ornatus has just one minor denticle (fig. 37H). Similar to T. ornatus, T. pectinis, A. gravieri, as well as both species of Neoanchistus (although the structures on the illustrations of N. cardiodytes of Bruce (1975a) are difficult to identify) bear none or one small denticle on the flexor margin (fig. 29E). The elusive T. liui also has no accessory teeth (Li et al., 2004). Interestingly, the species in the more derived clade of Anchistus, comprised of A. australis, A. demani, and A. miersi, show a presence of a larger accessory tooth, most apparent in A. miersi (figs. 5L, M, 6J, 16G). In contrast, the microscopic spinules which can be found on the dorsal surface of the unguis, can exclusively be found in the more derived lineages, and is not found in Ensiger and Dasella. Paranchistus armatus exhibits a few microspinules on the unguis, although preliminary sem-images prove that these structures are not homologous (de Gier et al., unpublished observation).

Conclusions

New distributions, hosts, and classification

In this study, numerous new records of distribution ranges and host affiliations are presented, summarized in table 2. In addition, this study establishes three new genera, and resulted in some additional taxonomic changes (table 2).

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Supplementary material

Supplementary material is available online at: https://doi.org/10.6084/m9.figshare.22310059.