Ecomorphological convergence in the walking leg dactyli of two clades of ascidian- and mollusc-associated shrimps (Decapoda: Caridea: Palaemonidae).

Symbiotic species, living within or on the surface of host organisms, may evolve a wide range of adaptations as a result of various selection pressures, host specificity of the symbiont and the nature of the symbiosis. In tropical marine coral reef ecosystems, palaemonid shrimps (Crustacea: Decapoda: Caridea) live in association with at least five different invertebrate phyla. Host switches between (distantly) related host groups, and the thereby associated selection pressures were found to play a major role in the diversification of these shrimp lineages, giving rise to various host-specific adaptations. Two lineages of palaemonid shrimp, which have switched from an ectosymbiotic association towards endosymbiosis, are studied for their morphological diversification and possible convergence. Special attention is given to the between-phyla host switches involving ascidian and bivalve hosts, which are characteristic for these lineages. Using landmark-based (phylo)morphospace analyses and Scanning Electron Microscopy, the walking leg dactylus shape and the microstructures on these dactyli are studied. No specific bivalve- or ascidian-associated morphotypes were found, but morphological convergence in dactylus morphology was found in various species within the two studied clades with similar host groups. In addition, multiple lineages of bivalve-associated species appear to be morphologically diverging more than their ascidian-associated relatives, with 'intermediate' morphotypes found near host-switching events.

The marine palaemonid shrimps (Crustacea, Deapoda, Caridea) of the Dutch Caribbean.

Species of the decapod family Palaemonidae are common components of tropical coastal waters and coral reefs. The majority of these species are symbionts of various invertebrate phyla. Despite a long history of research on their species diversity in the Dutch Caribbean, recent field expeditions have yielded much new information. Combined with examinations of specimens housed in Naturalis Biodiversity Center and information from literature, a comprehensive list of Dutch Carribean palaemonids is provided. Newly collected material was primarily identified via morphological analyses. Additional molecular phylogenetic analyses based on mitochondrial COI and 16S and nuclear Histone 3 (H3) genes were conducted in search of cryptic species on the one hand and to check conspecifity in species that were found on multiple host species on the other hand. In total, 46 species are here listed for the Dutch Caribbean of which 24 are here recorded for the first time for one of the islands. One species new to science was discovered and is herein described. Sixty new host associations are recorded. In light of biodiversity loss and increasing anthropogenic pressure on declining coral reefs, documenting the diversity of palaemonids and other coral reef species to provide baseline data takes on a new urgency.

A new species of scleractinian associated shrimp of the genus Palaemonella (Crustacea, Decapoda, Palaemonidae) with a redescription of Palaemonella orientalis Dana, 1852.

A new species of Palaemonella, P. rubrolineata sp. nov., is described on the basis of material collected from pocilloporid corals in Indonesia and Vanuatu. The new species is most closely related to P. orientalis, another tropical Indo-West Pacific species usually found in association with pocilloporid and acroporid corals. The new species can be distinguished from P. orientalis based on the presence of a hepatic spine, the more slender rostrum, body and longer appendages, the pleura of the fifth abdominal segment having a posteroventral tooth, the absence of distal rows of long serrate setae on the fingers of the first pereiopods, and in having the cutting edges of the second chela as well as the joints of the pereiopods dark red colored.

Redescription of Paraclimenes gorgonicola (Bruce, 1969) (Crustacea: Decapoda: Palaemonidae) and establishing P. franklini (Bruce, 1990) as its junior synonym.

The octocoral associated species Paraclimenes gorgonicola is a deep-sea palaemonid shrimp briefly described in Bruce (1969) without illustrations. Paraclimenes franklini, the type species of the genus Paraclimenes, has been considered as a valid species and distinguished from P. gorgonicola by the presence of articulated postrostral teeth on the carapace. Paraclimenes gorgonicola is herein fully redescribed and illustrated on the basis of the type series which is deposited in Naturalis Biodiversity Center, Leiden, The Netherlands and recently collected specimens from shallow waters around Jejudo Island, Korea, and compared with P. franklini. It is demonstrated that both taxa are conspecific and thus P. franklini is considered to be a junior synonym of P. gorgonicola.

Odontonia kerangcaris sp. nov., a new bivalve-associated shrimp (Crustacea, Decapoda, Palaemonidae) from East Kalimantan, revealing intrageneric host switching.

A new species of bivalve mollusk dwelling palaemonid shrimp of the genus Odontonia is described from the Berau Islands, East Kalimantan, Indonesia. This is the only Odontonia species recorded as a symbiont of a bivalve mollusk, all other congeners are known to associate with solitary ascidians. The new species belongs to the group wherein the dactylus of the ambulatory pereiopods has an accessory tooth. It differs from these species in the absence of a forward directed proximal tooth on the flexor margin of the corpus of the ambulatory dactyli. It also lacks the small denticles posterior to the distoventral accessory tooth on the dactylar corpus.

Two new species of Hippolyte from the Tropical Central and East Atlantic (Crustacea, Decapoda, Caridea).

Two new species of the caridean shrimp genus Hippolyte Leach, 1814 [in Leach, 1813-14] are described from the Tropical Central and East Atlantic. Hippolyte cedrici sp. nov., from Príncipe and São Tomé, can be distinguished from both the related H. holthuisi Zariquey Álvarez, 1953 and H. varians Leach, 1814 on the basis of rostral dentition, as well as meristics of the ambulatory pereiopods. Hippolyte karenae sp. nov., from St. Helena, is morphologically similar to H. coerulescens (Fabricius, 1775) and H. obliquimanus Dana, 1852, by having a well-developed tooth on the outer angle of the first peduncular article of the antennula. It differs from these species, amongst other characters, primarily in the armature of the ambulatory dactyli. Specimens were collected from hydrozoan, antipatharian and alcyonarian cnidarians.

Alpheus leptochiroides De Man, 1909, a poorly known deep-water snapping shrimp with a unique third maxilliped (Malacostraca: Decapoda: Alpheidae).

Alpheus leptochiroides De Man, 1909, a poorly-known species originally described from the Kai Islands in eastern Indonesia, is reported from Kavieng, eastern Papua New Guinea, representing only the second record of this snapping shrimp and slightly extending its distribution range into the tropical western Pacific. The original description was based on a relatively young specimen, whereas the Kavieng specimen is clearly an adult male. Most importantly, several rather important characters of the species were omitted and/or not illustrated by De Man, including the unique and diagnostic rounded cuticular expansions on several areas of the third maxilliped, not present in any other alpheid shrimp. Therefore, a full redescription of the species is provided, with new detailed illustrations.

On a collection of deep-water shrimp (Crustacea, Decapoda) from the Dutch Caribbean, with the description of a new species of Pseudocoutierea.

A collection of shrimp from deep reefs in the Dutch Caribbean is described. Most material originates from the Bonaire deep reef expedition (2013) by Wageningen Marine Research of Wageningen University. Some additional material was available from dives on Curaçao (2014). A new species of Pseudocoutierea Holthuis was recognized in the material collected off Bonaire. The new species is described and illustrated and its position in the phylogeny of the genus Pseudocoutierea analyzed. A key to the species in the genus is presented.

A new stygobiont species of Halocaridinides Fujino Shokita, 1975 (Crustacea, Decapoda, Caridea, Atyidae) from caves on Socotra Island (Yemen), with notes on the genus.

We describe a new species of stygobiont atyid shrimp of the genus Halocaridinides Fujino Shokita, 1975 from subterranean brackish and freshwater environments on Socotra Island (Yemen). This is the first atyid shrimp discovered in the Socotra Archipelago. This Socotran endemic is the second species of Halocaridinides recorded from an Indian Ocean island and the first to occur in non-anchialine environments. The new species is characterized by the absence of eye pigmentation, a reduced rostrum and the presence of a single spine in the uropodal exopod diaeresis. Morphological variability in the robustness of the first and the second chelipeds, particularly obvious in the chelae, may indicate local speciation or phenotypical plasticity. At both extremes of the variation, animals with most slender (tenuis type) or robust (robustus type) morphologies occur. We discuss the Indo-Pacific distribution of the genus and the potential origin of the new Socotran species. An amended diagnosis for the genus and a key to all species are included.

Odontonia plurellicola sp. n. and Odontonia bagginsi sp. n., two new ascidian-associated shrimp from Ternate and Tidore, Indonesia, with a phylogenetic reconstruction of the genus (Crustacea, Decapoda, Palaemonidae).

Two new species of palaemonid shrimp associated with ascidian hosts, Odontonia bagginsisp. n. from Tidore and Odontonia plurellicolasp. n., from Ternate, Indonesia are described and figured. Through phylogenetic analyses based on both morphological and molecular datasets (mitochondrial Cytochrome c oxidase subunit I gene and the 16S mitochondrial ribosomal gene) of the genus Odontonia, the phylogenetic positions of the new species have been reconstructed. Scanning Electron Microscopy has been used to observe additional characters on dactyli of the ambulatory pereiopods. Odontonia plurellicolasp. n. appears to be more closely related to O. simplicipes and O. seychellensis, but it differs most notably in the morphology of the rostrum and mouthparts. Odontonia plurellicolasp. n. appears to be the only Odontonia species living inside a phlebobranch ascidian Plurella sp. Odontonia bagginsisp. n. is closely related to O. sibogae, but differs markedly in the abundance of setae on the propodi of the ambulatory pereiopods. In the present paper, O. maldivensis Fransen, 2006 is regarded as a junior synonym of O. rufopunctata Fransen, 2002 based on both morphological and molecular aspects.

Multiple origins and strong phenotypic convergence in fish-cleaning palaemonid shrimp lineages.

Several species of palaemonid shrimps are known to act as fish-cleaning symbionts, with cleaning interactions ranging from dedicated (obligate) to facultative. We confirmed five evolutionarily independent origins of fish cleaning symbioses within the family Palaemonidae based on a phylogenetic analysis and the ancestral state reconstruction of 68 species, including 13 fish-cleaners from the genera Ancylomenes, Brachycarpus, Palaemon, Periclimenes, and Urocaridella. We focus in particular on two distantly related lineages of fish cleaning shrimps with allopatric distributions, the Indo-West Pacific Ancylomenes and the western Atlantic monophyletic Ancylomenes/Periclimenes group, which exhibit striking similarities in morphology, colouration and complex behaviour. Specifically, representatives of both lineages are similar in: (1) the general body shape and colour pattern; (2) the utilization of sea anemones as conspicuous cleaning stations; and (3) the use of sideways body swaying to visually promote their bright colour spots in order to attract fish clients. Such morphological, ecological and ethological convergences are apparently due to adaptations to fish cleaning linked to the establishment of similar modes of communication with fish clients in these species.

Multiple host switching events shape the evolution of symbiotic palaemonid shrimps (Crustacea: Decapoda).

The majority of the almost 1,000 species of Palaemonidae, the most speciose family of caridean shrimp, largely live in symbioses with marine invertebrates of different phyla. These associations range from weak epibiosis to obligatory endosymbiosis and from restricted commensalism to semi-parasitism, with the specialisation to particular hosts likely playing a role in the diversification of this shrimp group. Our study elucidates the evolutionary history of symbiotic palaemonids based on a phylogenetic analysis of 87 species belonging to 43 genera from the Indo-West Pacific and the Atlantic using two nuclear and two mitochondrial markers. A complementary three-marker analysis including taxa from GenBank raises this number to 107 species from 48 genera. Seven larger clades were recovered in the molecular phylogeny; the basal-most one includes mostly free-living shrimp, albeit with a few symbiotic species. Ancestral state reconstruction revealed that free-living forms likely colonised cnidarian hosts initially, and switching between different host phyla occurred multiple times in palaemonid evolutionary history. In some cases this was likely facilitated by the availability of analogous microhabitats in unrelated but morphologically similar host groups. Host switching and adaptations to newly colonised host groups must have played an important role in the evolution of this diverse shrimp group.

Let's be pals again: major systematic changes in Palaemonidae (Crustacea: Decapoda).

In recent years the systematic position of genera in the shrimp families Gnathophyllidae and Hymenoceridae has been under debate, with phylogenetic studies suggesting the families are not real family level units. Here, we review the molecular evidence as well as the morphological characters used to distinguish both families, leading to the conclusion that neither family is valid. Further, we studied the structural details of the single morphological character which distinguishes the two subfamilies (Palaemoninae, Pontoniinae) in Palaemonidae, as well as their phylogenetic relationship. As the supposed character distinction plainly does not hold true and supported by the phylogenetic results, the recognition of subfamilies in Palaemonidae is not warranted. As a consequence, all three supra-generic taxa (Gnathophyllidae, Hymenoceridae, Pontoniinae) are thus herein formally synonymised with Palaemonidae.

Periclimenes macrorhynchia sp. nov., a new hydrozoan-associated pontoniine shrimp (Crustacea, Decapoda, Palaemonidae) from North East Kalimantan, Indonesia.

A new species of pontoniine shrimp belonging to the 'Periclimenes obscurus species group' is described from the Berau Islands, North East Kalimantan, Indonesia. Specimens were obtained from aglaopheniid hydrozoans of the genus Macrorhynchia. The new species is here described and figured. Its affinities with related species are discussed and a DNA-barcode is provided.

Phylogenetic ecology of gall crabs (Cryptochiridae) as associates of mushroom corals (Fungiidae).

Coral-associated fauna is a relatively understudied topic. Hence, the nature of the relationship between an associated organism and its host is usually unknown. In the present study, the obligate associations between gall crabs (Decapoda: Cryptochiridae) and mushroom corals (Scleractinia: Fungiidae) are reviewed from a phylogenetic perspective. Based on field surveys, examination of museum material and a literature review, a total of 35 fungiid species have been found that act as hosts for four gall crab species. Fungiid-associated gall crabs appear to be more geographically widespread than previously known, with new records showing their occurrences from the Red Sea and western Indian Ocean all the way to the central Pacific Ocean. The obligate nature of the association between cryptochirids and their hosts makes them an ideal model taxon to test for possible cospeciation events. The congruence between their phylogenies was tested by using the program Jane 4.0, resulting in cospeciation and duplication events between the crabs and their host corals. The sharing of several closely related host coral species by the same gall crab species or genus may provide support to models indicating phylogenetic relationships within the Scleractinia.

A second discovery of Diapontonia maranulus Bruce, 1986 (Crustacea: Decapoda: Palaemonidae) in the Caribbean.

A second discovery of the echinoid associated shrimp species Diapontonia maranulus Bruce, 1986 is recorded from deep water off Curaçao, Leeward Islands of the Dutch Caribbean. The material is compared with the type description and paratypic material as well as with material of closely related species. A mtDNA COI barcode was obtained from the material. The systematic position of the genus is discussed.

Hamodactylus macrophthalmus spec. nov., a new coral-associated pontoniine shrimp (Decapoda, Caridea, Palaemonidae) from Indonesia.

A new coral-associated species of the genus Hamodactylus is described from Lembeh Strait, NE Sulawesi, Indonesia. The three other known species in the genus have been recorded in association with octocorals. The single ovigerous female specimen of the new species was collected from a scleractinian host. It can be easily separated from its congeners by the very long eyestalks and the chela of the second pereiopods having blunt tips of the fingers with tufts of long simple setae giving it an atyid-like appearance.

Caught in speciation? A new host for Conchodytes meleagrinae Peters, 1852 (Decapoda, Caridea, Palaemonidae).

During fieldwork in 2009 at Ternate, Indonesia, a pair of a pontoniine shrimp species belonging to the genus Conchodytes was collected from a bivalve mollusk of the genus Spondylus. This constitutes the first record of a species of the genus Conchodytes associated with a spondylid host. The specimens can be distinguished from other known Conchodytes species based on both morphology and colour pattern. Its COI barcode however, strongly resembles those obtained from three specimens of C. meleagrinae and is nested in the C. meleagrinae clade of the reconstructed phylogeny. Based on morphology and colouration only the specimens associated with the Spondylus bivalve would have been described as a species new to science. The modest conflicting molecular data have lead the authors to fully describe and figure the Spondylus associated specimens and compare them with the Pinctada associated specimens. Based on the present information it is decided not to give the Spondylus associated specimens the status as a distinct species but regard them as host-related (colour)morph of Conchodytes meleagrinae.

A new species of the sponge-associated pontoniine shrimp genus Nippontonia Bruce & Bauer, 1997 (Decapoda, Caridea, Palaemonidae) from Sabah, Malaysia.

A sponge-associated species of the genus Nippontonia new to science is described from Semporna, Sabah, Malaysia. The only other species in the genus is also known to be a sponge-dweller. The new species can be distinguished from its con- gener by a suite of characters mainly of the anterior appendages.