Hayato Tanaka

Tokyo Sea Life Park

The mating behaviour of the interstitial ostracod Parapolycope spiralis Tanaka & Tsukagoshi, 2010 is reported here for the first time. This species is adapted to an interstitial environment, and is typified by having tiny body size and being completely blind. In this paper it is presumed that the characteristics of the mating behaviour are typical...

We report the first direct evidence for the transoceanic transport of living marine Ostracoda. Seven benthic, phytal species, Sclerochilus verecundus Schornikov, 1981, Sclerochilus sp. 1, Sclerochilus sp. 2, Obesostoma cf. setosum (Okubo, 1977), Obesostoma sp., Paradoxostomatidae sp., and Xestoleberis setouchiensis Okubo, 1979, were transported in...

This study reports the taxonomy, ecology and evolution of interstitial Ostracoda (Crustacea). Taxonomy and ecology of interstitial ostracods from river mouth were discussed. High salinity tolerance of the interstitial ostracods living river mouth was proven by field distribution and laboratory experiment. The author hypothesizes that ancestral mari...

Chelonocytherois omutai gen. et sp. nov., is found on the back of female loggerhead sea turtles on the nesting beach of the Yakushima Island, Kagoshima Prefecture, Japan. The present study provides the first species-level identification and description of Ostracoda as sea turtle epibionts. The new genus and species, which belongs to the family Para...

Keysercythere reticulata sp. nov. and Redekea abyssalis sp. nov. , collected from the wood fall submerged in the Kuril-Kamchatka Trench (Northwestern Pacific), are only the second records of the naturally occurring, wood-associated ostracod fauna from a depth of over 5000 m. At the same time, K. reticulata is the second and R. abyssalis is the thir...

A new species Polacanthoderes shiraseae sp. nov. from three Antarctic regions (off Cape Darnley, off Totten Glacier, and in Lützow-Holm Bay) is described. In addition, type species of Polacanthoderes, Polacanthoderes martinezi, is redescribed. The new species is distinguished from P. martinezi by the presence of conspicuously thick lateroventral ac...

Three infaunal apodid sea cucumbers collected in Kushimoto, Shirahama, and Susami, in the southern coast of Wakayama, Japan are described. They have different morphological characteristics in body color, ossicle arrangement, and internal organs, each other. First species, animal displays a large body size (approximately 70–150 mm) and pale body col...

We describe the cypridoidean ostracod Cavernocypris hokkaiensis sp. nov. from riverbed sediments in an alpine stream at an elevation of ca. 1850 m in the Taisetsu Mountains, Hokkaido, Japan. This species differs from congeners in having (1) the outer surface of the carapace smooth, with sparse, tiny setae, but without shallow pits; (2) the carapace...

Ostracoda is a diverse group of tiny crustaceans. Although more than 9330 extant species have been described, whole-mitogenomic data were available for only five species. Here we present a complete mitogenomic sequence for an additional species, the parthenogenetic podocopan ostracod Heterocypris spadix. The mitogenome is 15,205 bp long and contain...

We describe the cypridoidean ostracod Heterocypris spadix sp. nov. from brackish water on Okinawa Island, Japan. The species closely resembles Heterocypris salina (Brady, 1868) but differs in that (1) the marginal infolds on valves are less developed, (2) the tubercles on the anterior margin of the right valve are completely covered by the selvage...

We describe Obesostoma crinophilum sp. nov. (Ostracoda: Podocopida: Paradoxostomatidae) obtained from the body surface of the feather star Antedon serrata A. H. Clark, 1908 (Crinoidea: Comatulida: Antedonidae). This is the first report of Ostracoda associated with Crinoidea. None of the highly specialized appendages and/or carapace that are related...

In Thailand, two species of rhizostome jellyfish, Rhopilema hispidum and Lobonemoides robustus , are commercially harvested. The cnidomes, nematocyst size and toxicities were compared between these species. Rhopilema hispidum and L. robustus each had four types of nematocysts on their oral arms. For R. hispidum , these nematocyst types included two...

Productivity and environmental stress are major drivers of multiple biodiversity facets and faunal community structure. Little is known on their interacting effects on early community assembly processes in the deep sea (>200 m), the largest environment on Earth. However, at hydrothermal vents productivity correlates, at least partially, with enviro...

Three new species of echinoderid kinorhynchs are described from Daidokutsu, a submarine cave in Ryukyu Islands, Japan. Echinoderes gama sp. nov. is characterized by the presence of middorsal acicular spines on segments 4–8; lateroventral acicular spines on segments 7–9; lateroventral tubes on segment 5; sublateral tubes on segment 8; laterodorsal t...

Ostracod genus Heterodesmus Brady, 1866 is known thus far to contain only three species: H. adamsii Brady, 1866; H. apriculus Hiruta, 1992; and H. naviformis (Poulsen, 1962). This genus has been recorded from the Sea of Japan, and the coastal areas of Thailand and Vietnam. The main generic character is the presence of antero-dorsal and postero-dors...

The present study describes Pontopolycope orientalis sp. nov. (Polycopidae), which was collected from the shallow sandy bottom off of Nagannu Island, Okinawa Prefecture, southwestern Japan. This new species is the first living representative of Pontopolycope from the Indo-Pacific region. We also provided a key to identifying five living congeners t...

One of the major crustacean groups, Maxillopoda had accommodated Mystacocarida, Copepoda, Thecostraca, Tantulocarida, Ostracoda, Branchiura, Pentastomida, and some fossil taxa, and was generally defined by some combinations of the following characters: body tagma composed of 5 cephalic, 6 (or 7) thoracic and 5 (or 4) abdominal somites; male gonopo...

In the present study, we describe two new marine species, Microloxoconcha toyoshioae n. sp. and M. sublittoralis n. sp., collected from the sandy bottom in the western part of Japan, from the depths of approximately 20 to 30 m and 50 m, respectively. This represents the first record of this genus from such depths, since all 10 previously described...

Living cytheroid ostracod fauna from South Korea is very poorly known, and so far only 12 species have been reported in the taxonomic literature with detail description. We describe one new species, Xestoleberis hujeongensis n. sp., and report three other cytheroid ostracods: X. setouchiensisOkubo, 1979; X. sagamiensis Okubo, 1976; and Hemicytherur...

This paper described Xylocythere sarrazinae sp. nov. (Ostracoda: Cytheroidea: Cytheruridae: Eucytherurinae), collected at 2196 m depth from the Grotto hydrothermal edifice (Main Endeavor Field, Juan de Fuca Ridge) in the northeastern Pacific Ocean. This new species was found living in association with Ridgeia piscesae tubeworm assemblages. It is th...

Hadal depths are one of the least explored ecosystems on the planet, with little data on biodiversity and even less on phylogegraphy of its inhabitants, especially of meiofaunal groups. Ostracods are an important component of meiofaunal communities, but with less than a dozen species described from the world’s ocean trenches. Therefore, six species...

Meiobenthos is a term usually referring to microscopic benthic organisms which pass through a 1 mm mesh sieve and are retained on a 32–63 μm one. Meiobenthos occurs in any aquatic environment, shows high species diversity as well as high biomass, and often plays an important role in ecological and evolutionary studies. However, the species diversit...

Lake Hachiro in Akita Prefecture is freshwater lake since 1966. Ishii et al. (2017) firstly reported four species of freshwater ostracods; Darwinula stevensoni, Bradleytriebella lineata, Cypridopsis vidua and Candona sp.1, from Lake Hachiro collected in 2015. This is the follow-up report of distribution and occurrence of freshwater ostracods from L...

Despite their high abundance and diversity, microfossil taxa adapted to a particular chemosynthetic environment have rarely been studied and are therefore poorly known. Here we report on an ostracod species, Rosaliella svalbardensis gen. et sp. nov., from a cold methane seep site at the western Svalbard margin, Fram Strait. The new species shows a...

This study describes a new species of cytheroid ostracod, Paradoxostoma koreana sp. nov., collected in Korea. In addition, three other cytheroid ostracods, P. setoense Schornikov, 1975, Loxoconcha pulchra Ishizaki, 1968, and Ishizakiella miurensis (Hanai, 1957), are reported with brief descriptions and images. Paradoxostoma setoense and L. pulchra...

A new apodid sea cucumber, Chiridota impatiens sp. nov., is described from the intertidal zone of Okinawa, Japan, and C. rigida Semper, 1867 is also described from the intertidal zone of Wakayama, as new to Japan. C. impatiens sp. nov. is approximately 60–70 mm, with 12 tentacles and 4–7 pairs of digits per tentacle, red or reddish brown in living...

The tri-spine horseshoe crab Tachypleus tridentatus is considered at risk and has been granted protection in Japan at least since the 1990s. The breeding areas in Okayama, Ehime and Saga prefectures, Japan, are protected by national and local laws, while in Hiroshima Prefecture the species has not been officially conserved by local administrations....

Two new taeniogyrinid sea cucumbers collected in the intertidal zone of southern Japan, Taeniogyrus verruculosus sp. nov. and Scoliorhapis sesokoensis sp. nov. are described. Both species possess a small body size (approximately 30–40 mm), light body color (translucent white in preserved specimens), ten tentacles, and numerous verrucous surfaces on...

Three new sea cucumbers collected in the intertidal and subtidal zone of southern Japan, Taeniogyrus mijim sp. nov., Rowedota chippiru sp. nov., and R. motoshimaensis sp. nov., are described. All three species display a small body size (approximately 10–20 mm), light body colour (primarily a transparent solid colour), and a small number of digits i...

Lake Hachiro in Akita Prefecture is freshwater lake since 1966. Unofficially, the ostracods have been recognized in Lake Hachiro since 1996; however, any information has never been published up to date. The present paper reports four species of freshwater ostracods; Darwinula stevensoni, Bradleytriebella lineata, Cypridopsis vidua and Candona sp.,...

A new commensal ostracod Asterositus ohtsukai n. g., n. sp. (Podocopida: Cytheroidea: Paradoxostomatidae) is described. This new taxon occurs on the ambulacral grooves and wreath of pedicellariae around superomarginal spines of the sea star Sclerasterias euplecta (Fisher) (Asteroidea: Forcipulatida: Asteriidae). Although the family Paradoxostomatid...

A new species of the cyclopinid genus Cyclopicina, C. toyoshioae sp. nov., was collected from the hyperbenthic layer off northern Kyushu Island, Japan; its description is based on two adult female specimens. This is the first record of the genus from the Indo-Pacific region. The new species can be distinguished from its two known congeners in: (1)...

The German-Russian expedition KuramBio II (Kurile-Kamchatka Biodiversity Studies II) with RV Sonne has been performed between 16.8.–26.9.2016 in the Kurile-Kamchatka Trench (KKT) region (SO-250). This expedition follows the Russian-German SoJaBio (Sea of Japan Biodiversity Studies) expedition to the Sea of Japan in 2010, the German-Russian KuramBio...

Deep-sea hydrothermal vent fields are among the most extreme habitats on Earth. Major research interests in these ecosystems have focused on the anomalous macrofauna, which are nourished by chemoautotrophic bacterial endosymbionts. In contrast, the meiofauna is largely overlooked in this chemosynthetic environment. The present study describes a new...

A new cladocopid ostracod species, Polycopissa okadai n. sp., is described from the marine interstitial environment of the Seto Inland Sea, western Japan. This is the second representative of this genus identified from the Indo-Pacific region. A detailed morphological observation of the carapace and appendage was performed using a scanning electron...

A new species of the priscomilitarid amphipod, Priscomilitaris heike, from the Seto Inland Sea, Japan, is named and described. This new species is the third species of Priscomilitaridae and the second species of Priscomilitaris. Additionally, nucleotide sequences of nuclear 28S rRNA and histone H3 as well as mitochondrial cytochrome c oxidase subun...

The oceanic calanoid copepod family Heterorhabdidae is unique in that it comprises both particle-feeding and carnivorous genera with some intermediate taxa. Both morphological and molecular (nuclear 18S and 28S rRNA) phylogenetic analyses of the family suggest that an evolutionary switch in feeding strategy, from transitions of typical particle-fee...

This study is a first report of an interstitial ostracod from Southeast Asia. The ostracod species, Paracobanocythere vietnamensis sp. n., was found in the marine interstitial environment of Phu Quoc Island, Vietnam. Thus far, three species of this genus have been described. The morphology of the carapace as well as the appendages of this new speci...

The ostracod genera Parapolycope Klie, 1939 and Kliecope Tanaka, Tsukagoshi & Karanovic, 2014 have a sexually dimorphic upper lip, and males use their lip during courtship. Here we study the male upper lip of 14 species in order to find homologous structures. For this purpose, the lip is divided into six homologous parts, determined by their relati...

During three cruises of TRV Toyoshiomaru, 4 families, 16 genera, and 36 species of Myodocopida (Ostracoda) were collected from the southern part of the Sea of Japan, Ariake Sea, and Seto Inland Sea. Because most (27/36) species are undescribed, current taxonomic studies are insufficient for these myodocopids. This paper supplies an illustrated guid...

A specimen of Hippa adactyla Fabricius, 1787, was collected from Blanche Bay, Papua New Guinea. Nuclear 18S and mitochondrial 16S ribosomal RNA gene sequences were examined for interspecies and intraspecies comparisons. The result suggests some genetic similarity and diversification of this species distributed widely in the Indo-Pacific. We also re...

Diverse aquatic organisms are living in the immediate freshwater environments such as the rice field, pond and ditch. This study reports a freshwater ostracod fauna of rice field and spring from Fuji and Fujinomiya, Japan. We found 14 species (13 genera), and Pseudocandona pratensis (Hartwig, 1901) is newly recorded from Japan. The morphological ch...

During a cruise of training and research vessel Toyoshiomaru in the Seto Inland Sea, western Japan, interstitial species belonging to seven genera in Myodocopa and Podocopa of Ostracoda (Crustacea) were found on sandy beds in shallow waters. Most of these interstitial ostracods have been considered to inhabit mainly the intertidal zone of sandy bea...

The morphology of non-genitalic structures in males is often associated with mating and courtship, and the evolution of those structures may cause speciation. In the present study, we describe a new species of marine interstitial ostracod from Japan. Morphological comparisons and molecular phylogenetic analysis based on ITS (internal transcribed sp...

Family Polycopidae is one of the more abundant and diverse taxa occurring in marine interstitial environments. Most of the interstitial polycopids are so far known from Japan and belong to the genus Parapolycope Klie, 1936. In this paper we describe another four new species from Japan. A new genus, Kliecope gen. nov. is erected to include one new s...

A new interstitial ostracod, Semicytherura uzushio sp. nov., is described from the southwest of Japan, and the details of the carapace characters of Semicytherura mukaishimensis Okubo, 1980 are redescribed. Semicytherura uzushio and S. mukaishimensis live interstitially in the intertidal and infralittoral zones, respectively. They have the smallest...

AbstractA new species of the genus Polycopetta Chavtur, 1981, Polycopetta quadrispinata sp. n. is described from the interstitial environment of Mihomasaki Beach in Japan. These observations showed some morphological peculiarities of Polycopetta quadrispinata sp. n. compared with its congeners; Polycopetta monneroni Chavtur, 1979, Polycopetta curva...

The male copulatory organ is recognized as a significant character for species taxonomy in the sexually reproducing Ostracoda. However, the genus Parapolycope has a simply shaped male copulatory organ consisting almost entirely of just the copulatory duct. In this study, two new species, Parapolycope psittacina sp. nov. and Parapolycope uncata sp....

A new species of ostracod, Semicytherura sagittiformis sp. nov., is described from a sandy beach in Shizuoka Prefecture, central Japan. It lives in pore-waters of marine sandy sediments and is ecologically associated with other interstitial ostracods (e.g., Parapolycope and Microloxoconcha). Semi-cytherura sagittiformis is one of the smallest speci...

Polycope japonica Hiruta, 1983 is transferred to the genus Parapolycope based on the morphology of the upper lip, antennula, antenna, mandibula, maxillula, and copulatory organ. In addition, a new species, Parapolycope digitolabrum sp. nov., is described and illustrated from a small sandy beach in Shimoda, Shizuoka Prefecture, central Japan.

Two new interstitial cladocopid ostracods are described from central Japan: Parapolycope oligohalina sp. nov, and Parapolycope spiralis sp. nov. These two species are the third and forth records of the genus Parapolycope Klie, 1936, respectively. Since P. oligohalina sp. nov. inhabits river mouth environments with low salinity at low tides, the wid...

Two new interstitial cladocopid ostracods are described from central Japan: Parapolycope oligohalina sp. nov, and Parapolycope spiralis sp. nov. These two species are the third and forth records of the genus Parapolycope Klie, 1936, respectively. Since P. oligohalina sp. nov. inhabits river mouth environments with low salinity at low tides, the wid...

Reproductive isolation and evolution of copulatory organ in eleven interstitial species of the genus Parapolycope (Ostracoda, Myodocopida) were discussed. The shapes of male ejaculatory duct are divided into the three types i.e., a helical tube type (Type H), a curved short tube type (Type S), and tapering long tube type (Type L). And the correlati...