Tomoyuki Komai

A revision of the genus Alvinocaris Williams and Chace (Crustacea: Decapoda: Caridea: Alvinocarididae), with descriptions of a new genus and a new species of Alvinocaris

The caridean shrimp genus Alvinocaris Williams and Chace, 1982 (Bresilioidea: Alvinocarididae) is revised based upon type material and newly obtained samples from various reducing environments of the deep‐sea floor of the world. All species are known from chemosynthetic communities associated with hydrothermal vents, brine or cold seeps. Eight named species are recognized in Alvinocaris, of which one is new, A. dissimilis sp. nov. from the hydrothermally influenced area of Minami‐Ensei Knoll, Mid‐Okinawa Trough. Alvinocaris dissimilis sp. nov. was confused with A. brevitelsonis in the original description of the latter species by Kikuchi and Hashimoto (2000). Seven previously described species (A. lusca Williams and Chace, 1982, A. markensis Williams, 1988, A. muricola Williams, 1988, A. stactophila Williams, 1988, A. longirostris Kikuchi and Ohta, 1995, A. brevitelsonis Kikuchi and Hashimoto, 2000, and A. williamsi Shank and Martin, 2003) are re‐described, and characters distinguishing these species are re‐assessed. Two species are confounded in the type series of A. stactophila Williams, 1988. The taxonomic status of the allotype of A. stactophila was not satisfactorily determined, as it appears to be an immature specimen. The geographic range of A. muricola, previously known only from cold seeps on the West Florida Escarpment, Gulf of Mexico, is greatly extended to the Barbados accretionary prism in the tropical western Atlantic and to the newly discovered seeps on the west equatorial African margin (Sibuet et al. 2002). In addition to these eight named species, five indeterminate or unnamed species of Alvinocaris have been reported, and most of them are under study by other authors. A new monotypic genus, Shinkaicaris, is established for Alvinocaris leurokolos Kikuchi and Hashimoto, 2000. The new genus is rather closer to Chorocaris Martin and Hessler, 1990, Opaepele Williams and Dobbs, 1995, and Rimicaris Williams and Rona, 1986 than to Alvinocaris in the structure of the eyes and the armament of the telson and pereopods. A key to aid in the identification of the eight species of Alvinocaris is given, although it is applicable only to adult specimens. The biogeography of Alvinocaris species is discussed.

A revision of the genus Pandalus (Crustacea: Decapoda: Caridea: Pandalidae)

The genus Pandalus Leach, 1814, is revised based upon the abundant material from collections in various museums or institutions in the world. Altogether 20 species are recognized which appear to form five groups. Nineteen species are recognized in Pandalus, three of which are described as new: P. curvatus from southern Japan, and P. chani and P. formosanus from Taiwan. Four informal species groups are also recognized within the genus: P. montagui group (P. montagui Leach, 1814; P. borealis Kroyer, 1838; P. goniuruStimpson, 1860; P. jordani Rathbun, 1902; P. tridens Rathbun, 1902; and P. eous Makarov, 1935); P. stenolepis group (P. stenolepis Rathbun, 1902; P. curvatus sp. nov.); P. hypsinotus group (P. hypsinotus Brandt, 1851; P. danae Stimpson, 1857; P. prensor Stimpson, 1860; P. gracilis Stimpson, 1860; P. gurneyi Stimpson, 1871; P. nipponensis Yokoya, 1933; P. teraoi Kubo, 1937; P. chani sp. nov.; and P. formosanus sp. nov.); and P. platyceros group (P. platyceros Brandt, 1851; and P. latirostris Rathb...

Taxonomic Review of the Hydrothermal Vent Shrimp Genera Rimicaris Williams & Rona and Chorocaris Martin & Hessler (Crustacea: Decapoda: Caridea: Alvinocarididae)

Abstract A taxonomic review of the two genera of the family Alvinocarididae (Decapoda: Caridea), Rimicaris Williams and Rona, 1986 and Chorocaris Martin and Hessler 1990, is presented based on study of type materials and/or supplemental material from recent collections. Two species of Rimicaris, R. exoculata Williams and Rona 1986 and R. kairei Watabe and Hashimoto 2002, and three species of Chorocaris, C. chacei Williams and Rona 1986, C. vandoverae Martin and Hessler 1990, and C. paulexa Martin and Shank 2005, are recognized. All species are exclusively associated with deep-water hydrothermal community. Close relationship between the two genera is confirmed by morphological characters, but the monophyly of Chorocaris is not corroborated. An examination of a good series of material from the Mid-Atlantic Ridge shows that juveniles of Rimicaris exoculata can be arranged in four sequential ontogenetic stages based on morphology. A dramatic change occurs at the size of 7.0 to 9.0 mm in the carapace length. The synonymies of Iorania concordia Vereshchaka 1996 and Rimicaris aurantiaca Martin, Signorovitch & Patel 1997 with Rimicaris exoculata, indicated from molecular evidence by Shank et al. (1998), are confirmed. Morphological differences between R. exoculata and R. kairei and those among C. chacei, C. vandoverae, and C. paulexa, are reassessed.

A new species of callianassid shrimp (Crustacea: Decapoda: Thalassinidea) from deep-water hydrothermal vents off Taiwan

ABSTRACT Nihonotrypaea thermophila, new species, is described on the basis of 26 specimens from a hydrothermally influenced field off northeastern Taiwan at depths of 128–320 m. This is the first callianassid shrimp to be reported from deep-water hydrothermal vents, and available data seems to suggest that the new species is vent-endemic. The new species is assigned to Nihonotrypaea Manning & Tamaki, 1998, a genus including three previously described species inhabiting coastal mud or sand flat areas in Japan and its adjacent waters. The new species is unique in the genus in having the antennal peduncle distinctly longer than the antennular peduncle.

ON STABILISING THE NAMES OF THE INFRAORDERS OF THALASSINIDEAN SHRIMPS, AXIIDEA DE SAINT LAURENT, 1979 AND GEBIIDEA DE SAINT LAURENT, 1979 (DECAPODA)

The names Gebiidea and Axiidea, erected by de Saint Laurent (1979), have priority over others for the two infraorders of shrimps previously included in Thalassinidea. Importantly, Thalassinidea are not monophyletic and the name should be replaced. Gebiidea and Axiidea, besides having priority and describing two monophyletic taxa, are now in common use (130 citations) and are more stable than alternative schemes proposed by Sakai (2005 and later). The history of the names of higher taxa applied to these groups is reviewed, and all family-group taxa listed.

Records of species of the hippolytid genus Lebbeus White, 1847 (Crustacea: Decapoda: Caridea) from hydrothermal vents in the Pacific Ocean, with descriptions of three new species

Five species of the hippolytid shrimp genus Lebbeus White, 1847 are reported from various deep-water hydrothermal ventsites in the Pacific Ocean: L. laurentae Wicksten, 2010 from the East Pacific Rise 13°N; L. wera Ahyong, 2009 from theBrothers Seamount, Kermadec Ridge, New Zealand; L. pacmanus sp. nov. from the Manus Basin, Bismarck Sea; L. shinkaiae sp. nov. from the Okinawa Trough, Japan; and L. thermophilus sp. nov. from the Manus and Lau basins, south-western Pacific. Lebbeus laurentae is fully redescribed because the original and subsequent descriptions are not totallydetailed. Differentiating characters among the three new species and close allies are discussed. Previous records of Lebbeus species from hydrothermal vents are reviewed.

In-situ Observations of Symbionts on Medusae Occurring in Japan, Thailand, Indonesia and Malaysia

During an ecological investigation on symbionts of medusae in Eastern and Southeastern Asian waters, seven species of hydro- and scypho-medusae were found to harbor a wide variety of invertebrates and fi shes: the isopod Idotea metallica and the nudibranch Fiona pinnata on the chondrophoran Vellela vellela; the actiniarian Peachia quinquecapitata on the leptomedusa Aequorea coerulescens; the butterfi sh Psenopsis anomala and the hyperiid amphipod Hyperia galba associated with the semaestome Chrysaora melanaster; H. galba on the semaestome Aurelia limbata; metacercariae of three species found in the mesogloea of a semaestome, Aurelia sp.; the ophiuroid Ophiocnemis marmorata, the caridean shrimp Latreutes spp., and the shrimp scad Alepes djedaba on the rhizostome Rhopilema hispidum; the swimming crab Charybdis feriata and A. djedaba on the rhizostome Versuriga anadyomene. Juveniles of benthic organisms such as crabs and ophiuroids seem to become hitchhikers for dispersal, while juvenile fi sh utilize medusae as refugia against predation. Since the previous and present studies have shown that edible rhizostomes are associated with many kinds of symbionts, fi sheries for these jellyfi shes possibly hinder the recruitment of symbionts such as decapods, ophiuroids and fi sh.

A new distinctive species of pagurid hermit crab (Crustacea: Decapoda: Anomura) from Japan

Abstract A new species of pagurid hermit crab, Pagurus decimbranchiae, is described and illustrated based on 20 specimens collected from shallow waters of the Pacific coast of Japan ranging from Boso Peninsula to Tanegashima Island. It is quite distinctive in having the rudimentary arthrobranch on the third maxilliped represented by a single bud, however close morphological similarity is found between the new species and P. moluccensis Haig and Ball. Comparisons are also made among other species, including P. boriaustraliensis Morgan, P. sp. cf. boriaustraliensis sensu Rahayu and Komai (2000) and the members of the P. anachoretus group. The present generic assignment of the new species should be considered provisional, as more extensive study is needed to investigate phylogenetic relationships of the new species and the other species of Pagurus.

A NEW SPECIES OF THE GENUS CALAXIOPSIS (DECAPODA: THALASSINIDEA: CALOCARIDIDAE) FROM JAPAN

A new species of calocaridid thalassinidean shrimp of the genus Calaxiopsis is described based on a single male specimen from Boso Peninsula, central Japan. It is related to C. serrata, but is readily distinguished from the latter in the unarmed submedian carinae on the gastric region, ventrally unarmed abdominal pleura, much shorter antenna! acicle and rudimentary podobranchs of the third maxilliped to third pereiopods, which lack normally developed gill filaments. The discovery of the new species shows that the development of the podobranchs on the third maxilliped to third pereiopods is variable within the genus. A check list of all known species of Axiidae and Calocarididae from the northwestern Pacific is included.

A new echiuran-associated snapping shrimp (Crustacea: Decapoda: Alpheidae) from the Indo-West Pacific.

Alpheus echiurophilus sp. nov. (Crustacea: Decapoda: Caridea: Alpheidae) is described based on material from Japan (Ryukyu Islands) and Vietnam (Nha Trang Bay); an additional, morphologically slightly different specimen from Madagascar (Nosy-Bé) is preliminarily referred to A. cf. echiurophilus sp. nov., awaiting collection of additional material and/or genetic comparison. All specimens of the new species were collected from burrows of thalassematid echiurans, either on intertidal and shallow subtidal sand-mud flats or in the mixed sand-gravel-rock intertidal. Alpheus echiurophilus sp. nov. belongs to the A. leviusculus species group, being morphologically closest to the Indo-West Pacific A. leviusculus Dana, 1852, A. hululensis Coutière, 1905, A. ladronis Banner, 1956, and the western Atlantic A. zimmermani Anker, 2007. The new species can be separated from all of them by a combination of morphological characters and also appears to have a diagnostic colouration.