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Abstract
The family Anchistioididae comprises a single genus Anchistioides with three species: A. compressus and A. willeyi from the tropical Indo-West Pacific, and A. antiguensis from the tropical West Atlantic. The two Indo-West Pacific species are known to be symbionts of sponges. Material collected in recent years throughout the Indo-West Pacific yielded range extensions as well as new host records. This material is herein described and their infraspecific morphological variation discussed.
Abstract
A new sponge-associated species, Paraclimenaeus michaeli sp. nov. from Sulawesi, Indonesia, and Singapore, is described and illustrated. The new species can be distinguished from its congenerics by: (1) the downwards curved rostrum with 2 acute dorsal teeth subdistally, (2) the absence of subdistal teeth on the fixed finger of the major second chela, (3) the pairs of dorsal telson spines at about 0.33 and 0.66 of the telson length, (4) the caudal fan sparsely setose, and (5) the second pereiopods without subdistal teeth on fixed finger. To evaluate its relationship with congenerics and species of the related genera Apopontonia and Climeniperaeus, a phylogenetic analysis based on the 16S mitochondrial gene is presented. A key for the identification of the species in Apopontonia, Climeniperaeus and Paraclimenaeus is proposed.
Abstract
A new sponge-associated species, Paraclimenaeus michaeli sp. nov. from Sulawesi, Indonesia, and Singapore, is described and illustrated. The new species can be distinguished from its congenerics by: (1) the downwards curved rostrum with 2 acute dorsal teeth subdistally, (2) the absence of subdistal teeth on the fixed finger of the major second chela, (3) the pairs of dorsal telson spines at about 0.33 and 0.66 of the telson length, (4) the caudal fan sparsely setose, and (5) the second pereiopods without subdistal teeth on fixed finger. To evaluate its relationship with congenerics and species of the related genera Apopontonia and Climeniperaeus, a phylogenetic analysis based on the 16S mitochondrial gene is presented. A key for the identification of the species in Apopontonia, Climeniperaeus and Paraclimenaeus is proposed.
Over the last century, a large body of literature emerged on mechanisms driving speciation. Most of the research into these questions focussed on terrestrial systems, while research in marine systems lagged behind. Here, we review the population genetic mechanisms and geographic context of 33 potential cases of speciation with gene flow in the marine realm, using six criteria inferred from theoretical models of speciation. Speciation with gene flow occurs in a wide range of marine taxa. Single traits, which induce assortative mating and are subjected to disruptive selection, such as differences in host-associations in invertebrates or colour pattern in tropical fish, are potentially responsible for a decrease in gene flow and may be driving divergence in the majority of cases. However, much remains unknown, and with the current knowledge, the frequency of ecological speciation with gene flow in marine systems remains difficult to estimate. Standardized, generally applicable statistical methods, explicitly testing different hypotheses of speciation, are, going forward, required to confidently infer speciation with gene flow.
Abstract
The family Anchistioididae comprises a single genus Anchistioides with three species: A. compressus and A. willeyi from the tropical Indo-West Pacific, and A. antiguensis from the tropical West Atlantic. The two Indo-West Pacific species are known to be symbionts of sponges. Material collected in recent years throughout the Indo-West Pacific yielded range extensions as well as new host records. This material is herein described and their infraspecific morphological variation discussed.
Abstract
Pandalus brevis Rathbun, 1906, based on an Hawaiian specimen and never rediscovered until now, was found in Madagascar and is redescribed. The reexamination of Rathbun's type reveals that this species belongs to the genus Bitias Fransen, 1990, which with Billas stocki Fransen, 1990, includes now 2 species which are compared.
Periclimenes rathbunae Schmitt, 1924 is a western Atlantic symbiotic shrimp species mainly associating with anemones. Adult shrimps of P . rathbunae are characterised by an orange-white spotted colour pattern. During fieldwork along the coast of Curaçao (2013), morphologically similar, though generally smaller sized shrimps were collected from the stony coral Dendrogyra cylindrus Ehrenberg, 1834. These specimens were overall more translucent. This study elucidates the taxonomic status of the coral-associated specimens in relation to anemone-associated specimens of P. rathbunae and related anemone-associated species using one nuclear (histone H3, H3), a mitochondrial protein-coding (cytochrome oxidase subunit I, COI) and a mitochondrial ribosomal RNA (16S) gene. Molecular phylogenetic reconstructions clustered the coral-associated specimens with anemone-associated P. rathbunae within a distinct clade, revealing that the aberrant coral-associated shrimp specimens belong to P. rathbunae. It can be concluded that 1) the stony coral D. cylindrus is a host of P. rathbunae, constituting the first record of an association between a scleractinian coral and a palaemonid shrimp species in the Atlantic Ocean; 2) the colour pattern of P. rathbunae is a phenotypically plastic characteristic that varies with size and is depending on the host species; and 3) mean body size of P. rathbunae is smaller on D. cylindrus than on the anemone Stichodactyla helianthus. This raises interesting questions about patterns of host use for this species and warrants further in-depth field ecological study for this species.