Shift in symbiotic lifestyle as the major process shaping the evolution of pea crabs (Decapoda: Brachyura: Pinnotheroidea).

The pea crabs, superfamily Pinnotheroidea, are exceptional among brachyuran crabs in their diverse symbiotic associations involving both inquilinism and protective symbiosis. While this group presents a rare opportunity for evolutionary comparative study of host switching and morphological evolution in marine macroinvertebrates, previous phylogenetic studies have been focused on systematics. Here, we reconstructed the most extensive phylogeny of Pinnotheroidea based on two mitochondrial and six nuclear markers, with the aim of elucidating the host switching pathways and the correlation between symbiotic lifestyles and selected morphological adaptations. Ancestral state reconstruction of host association revealed a monophyletic origin of symbiosis in the form of inquilinism. Subsequent shifts in microhabitat preference for burrows or worm tubes, and the move to protective symbiosis, primarily in the switch to mollusc endosymbiosis, contributed to radiation in Pinnotheridae. Further parallel colonisations of echinoderms and tunicates occurred but did not lead to extensive diversification, except in the Clypeasterophilus + Dissodactylus lineage, which experienced a unique switch to echinoderm ectosymbiosis. The evolution of the third maxillipeds, carapace shape and ambulatory pereiopods suggests a rather strong coupling with the symbiotic lifestyle (whether inquilinism or protective symbiosis). Phenotypic diversity of these characters was higher among species engaged in protective symbiosis, with convergence in form (or function) among those sharing the same host affiliation. Species having different host affiliations or symbiotic lifestyles might also exhibit convergence in the form of the three morphological traits, suggesting a common adaptive value of the specialisations. Pinnotherid crabs overall exhibited a lower trait diversity than the also symbiotic palaemonid shrimps with comparable species diversity. This may plausibly be attributed to differences in potential for morphological modification to serve additional functions among the traits analysed in the two groups, the less frequent host switching and the less diverse host affiliations, and thus a less complicated evolutionary history in pinnotherids.

Two new species of Sagum Wilson, 1913 (Copepoda: Siphonostomatoida: Lernanthropidae) parasitic on reef fishes off the Ryukyu Islands.

Two new species of parasitic copepods, Sagum gurukun n. sp. and S. bitaro n. sp. (Siphonostomatoida: Lernanthropidae), are described based on specimens collected from the gill filaments of the double-lined fusilier Pterocaesio digramma (Bleeker) (Actinopterygii: Perciformes: Caesionidae) and the five-lined snapper Lutjanus quinquelineatus (Bloch) (Actinopterygii: Perciformes: Lutjanidae), respectively, caught off Iriomote-jima Island, the Ryukyu Islands, East China Sea, Japan. The findings bring the number of species of Sagum to 14. The two new species are similar in the morphology of the head and the legs 3 and 4 to the three congeners, S. folium Ho, Liu & Liu, 2011, S. paracaesionis Izawa, 2014 and S. vietnamiensis Kazachenko, Kovaleva, Nguyen & Ngo, 2017. Sagum gurukun n. sp. is differentiated from the three congeners by the proportions of the caudal rami, the absence of leg 5, and the shape of the legs 1 and 2. Sagum bitaro n. sp. differs from the three congeners and S. gurukun n. sp. by the presence of the conical leg 5 armed with an apical seta. A key to the species of the genus Sagum, based on the available information on female morphology in previous publications and the present study, is provided. To date, a total of 19 species of lernanthropid copepods considered valid are known in Japanese waters.

Morpho-Molecular Evidence for Polymorphism in the Mushroom Coral Cycloseris hexagonalis (Scleractinia: Fungiidae), with a New Phylogenetic Position and the Establishment of a New Genus for the Species.

Mushroom corals are reef corals of the family Fungiidae, which live in the tropical and subtropical Indo-Pacific region. Recently, most species of this family have been revised taxonomically based on morphological and molecular analyses. However, the phylogenetic position of Cycloseris hexagonalis ( Milne Edwards and Haime, 1848 ) has not been analyzed and remains unclear. This species is believed to show allometric growth by changing its corallum shape from hexagonal in juveniles to irregularly circular with an undulated corallum margin in mature individuals. However, these morphological changes have not been monitored and their genetic basis has not been confirmed. In the present study morphological and molecular phylogenetic analyses were performed to evaluate the identity of the morpho-types in C. hexagonalis and to clarify the phylogenetic and taxonomic position of the species. In the morphological analysis, we used 20 specimens of C. hexagonalis collected from around Iriomote Island, Okinawa, Japan, and identified four morphotypes. Moreover, the molecular phylogenetic analyses using mitochondrial COI and nuclear ITS markers showed that all morpho-types of C. hexagonalis together form an independent clade, indicating that they are all conspecific. Molecular phylogenetic comparison between this species and other fungiids revealed that the clade of C. hexagonalis is clearly distant from the Cycloseris clade as well as from clades representing other genera in the Fungiidae. Considering these data, we establish a monotypic new genus, Sinuorota, to accommodate C. hexagonalis.

Description of two new species of Arcania Leach, 1817, from the western Pacific Ocean and redescriptions of A. undecimspinosa De Haan, 1841, and A. elongata Yokoya, 1933 (Crustacea: Brachyura: Leucosiidae).

Arcania undecimspinosa De Haan, 1841, and A. elongata Yokoya, 1933, are redescribed, with a lectotype of A. undecimspinosa formally designated. Redescription of the two species revealed that there are several specimens and possible undescribed species that have been inaccurately recorded under the name of A. undecimspinosa and A. elongata. Two such species are described from the western and southern Pacific Ocean as new to science. These four species partially overlap their geographical distributions and are superficially similar to each other, but the present study shows that there are clear differences in the shapes of their male first gonopods, female vulvae, frontal lobes of the carapace and other morphological characters. Literature that cited A. undecimspinosa s.l. is also reviewed to highlight possible taxonomic problems.

New species of Latreillopsis Henderson, 1888 (Brachyura: Homolidae) and Neopalicus Moosa & Serène, 1981 (Brachyura: Palicidae) from the Hawaiian Islands.

Two new species of brachyuran crabs belonging to Latreillopsis Henderson, 1888 (Homolidae) and Neopalicus Moosa & Serène, 1981 (Palicidae) respectively are described from Maui, Hawai'i. The new species of Latreillopsis is distinguished from its nine congeners by a granular carapace and pereopods, a triangular G1, and by the distinctive ornamentation of its carapace and third maxillipeds; the new species of Neopalicus from its three congeners by the presence of three triangular anterolateral teeth, absence of extensions on the outer margins of the P3 and P4 propodi, dentate inner margins of the P3, P4 dactyli, and absence of ridges on the female abdomen. Also listed is Latreillia metanesa Williams, 1982 (Latreilliidae), recorded for the first time from the archipelago since its description from Albatross material collected in 1902.

A new genus and species of a submarine cave crab of the family Plagusiidae Dana, 1851 (Crustacea: Brachyura: Grapsoidea) from Okinawa Island, Ryukyu Islands, southwestern Japan.

Caligoplagusia okinawa n. gen. & n. sp., assigned to the brachyuran family Plagusiidae Dana, 1851 is described on the basis of a male and a female specimens collected from a semi-submerged marine cave on the limestone shore of Okinawa Island, Ryukyu Islands, southwestern Japan. The new monotypic genus is most similar to Euchirograpsus H. Milne Edwards, 1853 and Miersiograpsus Trkay, 1978 in that the frontal margin lacks a deep sublateral cleft adjacent to the orbit, but differs significantly by its subhexagonal carapace shape, the anterolateral margin of the carapace with three teeth including the external orbital tooth, the anterior margin of ambulatory meri each armed with a row of large teeth, and the greatly reduced eyes. The pale body colour, reduced eyes, the very elongate antennal flagellum, and long ambulatory legs are all typical brachyuran adaptations to living in cave environments. This is the first cave-dwelling species of the family Plagusiidae.

Two new species of freshwater crabs of the genus Heterochelamon Türkay & Dai, 1997 (Crustacea: Decapoda: Brachyura: Potamidae) from Guangxi Zhuang Autonomous Region, southern China.

Heterochelamon tessellatum n. sp. and H. castanea n. sp. are described trom the Guangxi Zhuang Autonomous Region, southern China. Heterochelamon tessellatum n. sp. and H. castanea n. sp. are morphologically most similar to H. yangshuoense Türkay & Dai, 1997, and H. guangxiense Türkay & Dai, 1997, respectively. The new species can be differentiated from these allied species by differences in the shape of external orbital tooth, epibranchial tooth, and male first gonopod. The present study brings the number of Heterochelamon species to five. A key to species of the genus Heterochelamon is provided.

Recognition of Parapinnixidae Stevcic, 2005, and Tetriasidae fam. nov. in Pinnotheroidea De Haan, 1833 (Crustacea: Brachyura: Thoracotremata).

The systematic position of three aberrant pinnotheroid genera: Tetrias Rathbun, 1898, Parapinnixa Holmes, 1895 and Sakaina Serène, 1964, are reappraised. A new family, Tetriasidae fam. nov. is established for Tetrias, and Parapinnixidae Stevcic, 2005, is recognised for Parapinnixa and Sakaina. Tetriasids differ from all other pinnotheroids in that the articles of the palp of the third maxilliped (carpus, propodus and dactylus) are large and the dactylus is inserted at the distolateral corner of the propodus, whereas parapinnixids are distinctive in having the buccal cavern relatively small, subtriangular with the third maxilliped ischiomerus small, mesioproximally produced to form a triangular projection and is completely fused. The two families are phylogenetically distinct from the family Pinnotheridae based on the multi-locus gene tree, and are basal or near basal lineages in the Pinnotheroidea.

Morphological and phylogenetic study of Acanthosquilla Manning, 1963 (Stomatopoda: Nannosquillidae) mantis shrimps, with description of two new species from the Ryukyu Islands, Japan.

Three species of nannosquillid mantis shrimps, including two new species, Acanthosquilla ryukyuensis n. sp. and Acanthosquilla shoheii n. sp., are described based on specimens collected from the Ryukyu Islands, Japan. The two new species resemble A. derijardi Manning, 1970, but can be distinguished from A. derijardi by the following features: 1) rostral plate anterolateral corner forms almost a right angle; 2) the distal tip of the antennular somite dorsal process reaches or slightly falls short of proximal half of rostral plate; and 3) eighth thoracic somite (= TS8) posterior margin is black medially. Furthermore, A. ryukyuensis n. sp. and A. shoheii n. sp. are easy to identify by the bifurcated lateral tooth of the telson, and by the posterodorsal pattern of the telson, respectively. In this study, molecular analyses based on partial sequences of mitochondrial 12S and 16S ribosomal DNA, cytochrome oxidase subunit I (COI), and the partial nuclear gene of 28S ribosomal DNA recovers these three species of Acanthosquilla and A. multifasciata (Wood-Mason, 1895) (the type species of the genus) in a single clade. The resulting trees also suggest the polyphyly of Nannosquillidae but with low nodal support. Detailed examinations of the morphological and color features and DNA barcoding results allowed us to delineate intraspecific variations and interspecific differences. The number and shape of setae under the dorsal spine of raptorial claw carpus was found to be useful in distinguishing A. shoheii n. sp. from A. derijardi and A. ryukyuensis n. sp., while combinations of the coloration of the rostral plate, posterior margin of TS8 and posterodorsal surface of telson are useful to distinguish the three species.

Molecular evidence and differences in gonopod morphology lead to the recognition of a new species of the freshwater crab genus Candidiopotamon Bott, 1967 (Crustacea, Brachyura, Potamidae) from eastern Taiwan.

A new freshwater crab of the potamid genus Candidiopotamon Bott, 1967, is described from eastern Taiwan. Candidiopotamonpenglai sp. nov. is morphologically similar to C.rathbuni (De Man, 1914) from western Taiwan, but can be distinguished by the morphology of the male first gonopod (G1), as well as by their mitochondrial DNA (16S rRNA and COI genes). In the G1 of C.rathbuni, the subterminal segment shows a cline from robust in northern populations to slender in southern populations. In the G1 of C.penglaisp. nov., a distinctly larger and more distally directed keel-like projection is found on the distal inner edge of the terminal segment, with northern populations having an inward-curving subterminal segment and southern populations a straight subterminal segment. The genetic differentiation of the two species of Candidiopotamon within Taiwan is discussed, and morphological differences are compared. A key to the species of Candidiopotamon is also provided.

Redescription of Pinnixa haematosticta Sakai, 1934, its transfer to Indopinnixa Manning amp; Morton, 1987, and a reappraisal of Indopinnixa kumejima Naruse amp; Maenosono, 2012 (Decapoda: Brachyura: Pinnotheridae).

The poorly known pinnotherid crab, Pinnixa haematosticta Sakai, 1934, is redescribed on the basis of female holotype and additional specimens, including males and females, from Japan. The male characters of the species are documented for the first time. The species is transferred to Indopinnixa Manning Morton, 1987 because the male pleonal somites 35 are functionally fused, the telson is wide, and the maxilliped 3 with the dactylus is distinctly longer than the propodus. Indopinnixa kumejima Naruse Maenosono, 2012 is morphologically very similar to I. haematosticta n. comb., but a molecular phylogenetic analysis using partial fragments of the mitochondrial 16S rRNA gene supports the hypothesis that the two taxa as distinct. Morphologically, the two species are differentiated by the shape of the pereopod 4 merus (proportionally wider in I. haematosticta n. comb. than in I. kumejima). Our findings suggest that I. haematosticta n. comb. and I. kumejima are geographically distinct: I. haematosticta appears restricted to the Japanese mainland (Honshu to Kyushu) and Ohsumi Islands, while I. kumejima occurs in the Ryukyu and Ogasawara Islands.

A new species of alpheid shrimp tentatively assigned to Salmoneus Holthuis, 1955 (Decapoda: Caridea) from the Ryukyu Islands, Japan.

A new alpheid shrimp species, provisionally assigned to the genus Salmoneus Holthuis, 1955, is described and illustrated on the basis of three specimens extracted from intertidal soft sediments on seagrass beds at Iriomote Island, southern Ryukyu Islands, Japan. Salmoneus singularis n. sp. is highly distinctive within the genus in having a pair of postorbital spines on the carapace, otherwise showing some affinities to the species of the S. gracilipes Miya, 1972 group. The possession of paired spines on the dorsolateral surface of the carapace is shared with several members of Triacanthoneus Anker, 2010, which is undoubtedly closely related to Salmoneus. However, the new species cannot be placed in Triacanthoneus because of the absence of a mid-dorsal spine on the carapace.

Redescription of the brackish water crab Ptychognathus glaber Stimpson, 1858 based on the topotypic material from the Ogasawara Islands and new record of P. lipkei N.K. Ng, 2010 from Japan (Decapoda: Brachyura: Varunidae).

Examination of material from various Japanese localities clarified that the estuarine crab Ptychognathus glaber Stimpson, 1858 is possibly restricted to the Ogasawara Islands, Japan. Specimens from the Ryukyu Islands, thought to represent P. glaber, actually represent P. lipkei N.K. Ng, 2010 instead, previously known only from Cebu, the Philippines. Ptychognathus glaber is redescribed in detail, and differentiating characters between it and P. lipkei are reassessed. Previous literature records of P. glaber are reviewed in the light of our findings. Genetic analysis using partial sequences of the mitochondrial 16S rRNA gene suggests that P. glaber is genetically closer to P. ishii Sakai, 1939 than to P. lipkei, and thus P. ishii is also compared morphologically with P. glaber.

Semisubmersible oil platforms: understudied and potentially major vectors of biofouling-mediated invasions.

Biofouling has long been recognised as a major pathway for the introduction of non-indigenous species. This study records the decapods and stomatopod crustaceans fouling a semisubmersible oil platform dry docked for hull cleaning in Jurong Port, Singapore. Of the 25 species of decapods identified, 13 were non-indigenous and represent new records to Singapore waters. Of these, the crabs Glabropilumnus seminudus and Carupa tenuipes are known to be invasive in other parts of the world. The stomatopod, Gonodactylaceus randalli, is the first mantis shrimp recorded in a biofouling community. The richness and diversity of this fouling community, consisting of many vagile species, highlights the difference between platforms and ships. With the expansion of maritime oil and gas exploration, the threat posed by an expanded fleet of semisubmersible oil platforms translocating non-indigenous fouling communities across biogeographical boundaries is very serious. Scientists, policy-makers, and stakeholders should turn their attention to this growing problem.

Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae).

The genus Conchoecetes Stimpson, 1858, has long been considered to include three species: C. artificiosus (Fabricius, 1798), C. andamanicus Alcock, 1900, and C. intermedius Lewinsohn, 1984. The type species, C. artificiosus, has been assumed to be widely distributed throughout the Indo-West Pacific and a fourth species, C. conchifera (Haswell, 1882), from Australia, has been regarded as a synonym. The enigmatic and long overlooked "Caphyra pectenicola Adams, in Belcher, 1848" is shown to be a species of Conchoecetes occurring in Java, Singapore and the Gulf of Thailand. We review the status of these species, establish C. conchifera as a valid species, and describe five new species: C. atlas n. sp., C avikele n. sp., C. chanty n. sp., C. investigator n. sp. and C. pembawa n. sp. In this revision we recognize 10 valid species in Conchoecetes. They are distributed from Southern Africa, across the Indian Ocean to Australia and northwards to China. Formerly considered to be cosmopolitan, C. artificiosus is restricted to India, Sri Lanka Pakistan, as well as the Persian Gulf and Madagascar, while C. intermedius, first discovered near Madagascar, is shown to be the most widespread species occurring from Africa to China.

Biodiversity surveys reveal eight new species of freshwater crabs (Decapoda: Brachyura: Potamidae) from Yunnan Province, China.

Yunnan Province is known to host the highest species diversity of the true freshwater crabs in China; 50 species have been recorded from the province by 2017. In 2004, our team conducted a biodiversity survey of the freshwater crabs in Yunnan Province to determine how well the diversity of crabs in the area has been characterized. We collected a total of 25 species, of which nine species proved to be new to science, and eight of which are described here. These include four species of the genus Indochinamon Yeo & Ng, 2007, two species of the genus Potamiscus Alcock, 1909, and one species each of the genera Pararanguna Dai & Chen, 1985, and Parvuspotamon Dai & Bo, 1994. The new species of Pararanguna and Parvuspotamon represent the second species of respective genera, which are here redefined. Detailed comparisons with morphologically allied species are provided. Photographs of the type specimens of their comparative species which are poorly illustrated in the literature are also provided to allow better understanding of their morphology. This study brings the number of the freshwater crabs of Yunnan Province to 58. Since about 13.8% of the number of species (eight out of 58 species) is increased by surveys conducted within a relatively short period, it is most probable that the species diversity of this group is still understudied in Yunnan Province.

New records of species of the Polyonyx sinensis group (Crustacea: Decapoda: Anomura: Porcellanidae) from Japan, the Philippines, Singapore, and Malaysia, with descriptions of two new species.

Five species of the genus Polyonyx Stimpson, 1858 are reported from southern Japan, the Philippines, Singapore, and Peninsular Malaysia. All of them belong to the P. sinensis group, which is morphologically defined by having the dactyli of the ambulatory legs each with the dorsal claw being much smaller than the ventral claw. Two species are described as new to science, one each from Peninsular Malaysia and the Ryukyu Islands in Japan, and their affinities are discussed. Polyonyx boucheti Osawa, 2007, P. heok Osawa Ng, 2016, and P. thai Werding, 2001, are also newly reported from southern Japan, the Philippines, and Singapore. A key to the Indo-West Pacific species of the P. sinensis group is provided.

Helice epicure, A New Species of Varunid Mud Crab (Brachyura, Decapoda, Grapsoidea) from the Ryukyus, Japan.

Ngan Kee Ng, Tohru Naruse, and Hsi-Te Shih (2018) Helice epicure, a new species of varunid crab, is described from the Ryukyu Islands, Japan. The new species in the genus Helice De Haan, 1833 can be distinguished from its congeners by morphological differences in the chelae and suborbital crenulation. The morphological differences between the new species and a sister clade (the H. latimera complex, including H. latimera Parisi, 1918, H. tientsinensis Rathbun, 1931 and H. formosensis Rathbun, 1931) are supported by mitochondrial cytochrome oxidase subunit I (COI) divergences. However, the phylogenetic relationship within the H. latimera complex is unresolved for the time being.

A revision of the freshwater crab genus Hainanpotamon (Crustacea: Decapoda: Brachyura: Potamidae: Potamiscinae), with a redescription of Potamon (Potamon) orientale (Parisi, 1916) and descriptions of three new species.

The taxonomy of the potamid genus Hainanpotamon , from Vietnam, Laos, Hainan Island (China) and, purportedly, Okinawa Island (Japan) is reviewed. The type species, Potamon (Potamon) orientale (), is redescribed and a lectotype designated. In addition, three new species are described. The poorly known species Potamon (Geothelphusa) globosum , is assigned to Hainanpotamon and its taxonomy clarified, with a lectotype designated. A key to the nine species of Hainanpotamon is provided.

Rapid coral mortality following unusually calm and hot conditions on Iriomote, Japan.

Coral bleaching can be induced by many different stressors, however, the most common cause of mass bleaching in the field is higher than average sea surface temperatures (SST). Here, we describe an unusual bleaching event that followed very calm sea conditions combined with higher than average SST. Patterns of mortality differed from typical bleaching in four ways: 1) mortality was very rapid; 2) a different suite of species were most affected; 3) tissue mortality in Acropora spp. was often restricted to the center of the colony; 4) the event occurred early in summer. The two weeks prior to the event included 8 days where the average wind speed was less than 3 ms -1. In addition, SSTs in the weeks preceding and during the event were 1.0-1.5°C higher than the mean for the last 30 years. We hypothesize that this unusual bleaching event was caused by anoxia resulting from a lack of water movement induced by low wind speeds combined with high SST.