ON A SMALL COLLECTION OF CARIDEAN SHRIMPS (DECAPODA, CARIDEA) FROM INHACA ISLAND, MOZAMBIQUE

During a series of irregular visits to Inhaca Island, Mozambique in the years 1982-1987, J.H.C. Walenkamp, often aided by students and staff of the Faculty of Biology in Maputo, made extensive collections of littoral and infralittoral invertebrates. Among the extensive collections of Brachyura, several caridean shrimps were encountered, upon which we herein report. Cuapetes cf. ensifrons is recorded from Mozambique for the ﬁrst time


INTRODUCTION
In 1958 Macnae & Kalk published their book on the natural history of Inhaca Island, southern Mozambique.This Inhaca report is based upon collections acquired over many years and could be expected to be moderately complete.In 1 ) Corresponding author; e-mail: charles.fransen@naturalis.nlthis book they listed 34 species of caridean shrimps from Inhaca Island.The most complete checklist of the decapod Crustacea of southern Africa, including Mozambique, was compiled by Kensley (1981) from existing literature.This list included 65 marine caridean species from Mozambique.The most recent overview of the caridean fauna of Mozambique was published by Emmerson (2016).However, in his book less species are treated than in the work by Kensley (1981).
During a series of irregular visits to Inhaca Island, Mozambique in the years 1982-1987, J.H.C. Walenkamp, often aided by students and staff of the Faculty of Biology in Maputo, made extensive collections of littoral and infralittoral invertebrates.Among the extensive collections of Brachyura (Willems & Fransen, in prep.), several caridean shrimps were encountered upon which we herein report.

MATERIAL AND METHODS
Specimens were studied using a dissecting stereomicroscope (Zeiss Discovery.V8) and a compound microscope (Olympus BX53), both provided with a drawing tube.All drawn figures were performed by the first author.Drawings were scanned (Canon Canoscan 9000F) with a resolution of 600 dpi and subsequently mounted into plates using Adobe Photoshop software (Adobe Systems).Post-orbital carapace length (pocl.) was measured from the posterior margin of the orbit to the posterior margin of the carapace in dorsal midline; rostral characters (R) are formulated as R = number of postorbital dorsal teeth + number of dorsal teeth on rostrum proper/number of ventral rostral teeth.Field collection numbers are abbreviated as fcn.Specimens were deposited in the Naturalis Biodiversity Center (formerly Rijksmuseum van Natuurlijke Historie, RMNH), Leiden, The Netherlands.
The specimen described by Monod (1973) from New Caledonia somewhat resembles Latreutes bicornis (Kemp, 1925) in the dentition of the carapace and rostrum.The stylocerite is distally acute whereas this is rounded in specimens of L. mucronatus described by Kemp (1914, pl. 3 fig. 12) and Ledoyer (1969, fig. 7a) and the specimens at hand.
The long simple setae on the dorsal surface of the carapace have been noted in literature only for specimens with 3-4 postorbital teeth on the carapace (Ledoyer, 1969;Al-Kandari et al., 2020).This might be another indication that these specimens with 3-4 postorbital dorsal teeth belong to another species in the species complex.The specimens from Makassar Strait (RMNH.CRUS.D.1515) and Mozambique (RMNH.CRUS.D.16439) that were studied for comparison are similar to the holotype described by Dana (1852a, b) from Hong Kong in having only one postorbital dorsal tooth and are without the long simple setae on the dorsal surface of the carapace.
Biology.-There is a distinct sexual dimorphism in several characters including the dentition of the rostrum (see Kemp, 1914).In general, the males are slenderer than the females.Most records of the species are from shallow water areas with sea weeds.The species has been recorded once as an associate of a jellyfish (Hayashi & Miyake, 1968).
Family PALAEMONIDAE Rafinesque, 1815 Genus Cuapetes Clark, 1919 Cuapetes cf.ensifrons (Dana, 1852) (fig.4)  Remarks.-The specimen generally fits the description by Dana (1852aDana ( ,b, 1855) ) except for the number of ventral rostral teeth which is 3 in the type specimens and 2 in the present specimen.The diagnosis of C. ensifrons given by Chace and Bruce (1993) based on more reports on the species gives a broader range in rostral dentition: R = 1-2 + 5-6/2-3.In the present specimen, the rostrum just reaches beyond the scaphocerite, bears seven dorsal teeth of which one is postorbital and one at the level of the orbit, and two ventral teeth at some distance of the tip (fig.4A); supraorbital, antennal and hepatic spines are present (fig.4A,  B); infraorbital angle produced, pointed (fig.4B); third maxilliped with ultimate segment slightly shorter than penultimate segment, penultimate segment slightly shorter than antepenultimate segment, antepenultimate segment with 5 spines on distolateral margin, exopod slightly longer than antepenultimate segment (fig.4C); first pereiopods with carpus slightly longer than merus, chela as long as carpus, fingers slightly longer than palm (fig.4D); second pereiopods with meri armed with distoventral acute tooth (fig.4E); carpus with distomedial angular protuberance but not developed in a prominent tooth (fig.4G, H), fingers somewhat shorter than palm with teeth in the proximal half (fig.4F); ambulatory pereiopods with propodi with row of ventral spines of which those in distal part in pairs (fig.4I); unguis simple, slender, slightly curved (fig.4I); fifth pair of pereiopods almost reaching distal margin of scaphocerite with their dactyli.
Two other species of Cuapetes known from Mozambique possessing a supraorbital spine are C. demani (Kemp, 1915) and C. grandis (Stimpson, 1860) (see Barnard, 1955Barnard, , 1958)).These species differ from the present specimens in having Downloaded from Brill.com 03/08/2024 11:31:11AM via Open Access.This is an open access article distributed under the terms of the CC BY 4.0 license.https://creativecommons.org/licenses/by/4.0/ a prominent distomedial tooth on the carpus of the second pereiopods.Bruce (2004) questions the validity of C. ensifrons based on the variation in the armature of the second pereiopod carpus in C. grandis.The presence of an acute distal tooth defines C. grandis (Stimpson 1860) whereas the absence of such tooth is characteristic for C. ensifrons.In material from Queensland Australia, Bruce (2004) observed both forms.
The Inhaca specimen is also similar to C. longirostris (Borradaile, 1915) which also occurs in the area (Fransen, 1994).This species also has a supra-orbital tooth as well as the distoventral tooth on the merus of the second pereiopods, but is without a distomedial tooth on the carpus of the second pereiopods.It differs from C. ensifrons in the first pereiopod having a relatively shorter chela which is 0.6-0.7 of the carpus length and the carpus distinctly longer than the merus (see Borradaile, 1917, plate 54, fig. 11a, as Periclimenes (Falciger) affinis; Kemp, 1922, fig. 53a, as P. (Ancylocaris) proximus;and Holthuis, 1958, fig. 1b).In Cuapetes ensifrons the chela of the first pereiopod is almost as long as the carpus and the carpus is only slightly longer than the merus (see Dana, 1955, plate 38, fig. 1).The material of C. longirostris from the Seychelles and Eilat used for comparison here has slightly more slender pereiopods and shows the shorter chelae of the first pereiopods in comparison to the carpus than in the present material.The third maxilliped in the specimens studied from the Seychelles and Eilat have a row of 4-5 spines in the distal half of the penultimate segment similar to the specimen from Inhaca.
As the type material of C. ensifrons is no longer extant (Bruce, 2004), it will remain unclear what its taxonomic status is in relation to similar species like C. grandis and C. longirostris.As some differences with comparative material of the latter two species have been observed that agree with the diagnosis of C. ensifrons, the present specimen is here indicated as C. cf.ensifrons.
Cuapetes seychellensis (Borradaile, 1915) (fig.5) Remarks.-Although the present specimen is lacking the rostrum, it fits the rather brief type description of the species by Borradaile (1915).The carapace bears an antennal and hepatic tooth and several long simple setae dorsally (fig.5A); the eyestalks have an anterior obtuse tubercle (fig.5B); the scaphocerite overreaches the antennular peduncle and has the distal margin of the lamina rather broad and the distolateral tooth reaching the distal margin of the lamina (fig.5A,  B); the first pereiopods are slender with merus, carpus and chela of equal length, fingers slightly longer than palm (fig.5C); the second pereiopods are of equal length, slender, with carpus and merus of equal length, fingers slightly longer than palm, few teeth proximally on cutting edges (fig.5D, E); ambulatory pereiopods with spines on ventral margin of propodus, dactylus simple slightly curved (fig.5F).Borradaile (1915Borradaile ( , 1917) ) did not mention the tubercle on the eyestalk nor the long simple setae on the carapace.In his rather small specimen the distolateral tooth of the scaphocerite was overreaching the distal lamina and only the distal spines of the propodi of the ambulatory pereiopods were mentioned.
The description of specimens studied by Kemp (1922) from India and the Andamans is more extensive.The present specimen fits this description in all aspects although Kemp (1922) also did not mention the long simple setae on the dorsal surface of the carapace.Marin & Sinelnikov (2016) redescribed the species based on specimens from Vietnam.The present specimen from Mozambique fits this description, including the presence of the long simple setae on the dorsal surface of the carapace.
The comparative material studied from Thailand and New Caledonia is similar to the specimen from Mozambique.The material from Madagascar differs in the absence of the long simple setae on the dorsal surface of the carapace and the rostra seem to be more straight than in the other material.
Previous record from Mozambique by Barnard (1958).