OSTRACOD RESEARCH

at the Lake Biwa Museum, Japan


Robin James Smith

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Genus Ilyocypris Brady & Norman, 1889

Superfamily: Cypridoidea Baird, 1845
Family: Ilyocyprididae Kaufmann, 1900
Subfamily: Ilyocypridinae Kaufmann, 1900

Five species have been reported from Japan:

1. Ilyocypris angulata Sars, 1903

Figures in: Sars 1903 (carapace); Okubo 1974 (carapace and appendages); Victor & Fernando 1981 (carapace and parts of appendages); Zhai & Zhao 2014 (carapace and appendages).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Sexual in Japan (Okubo 1974). Asexual in China (Sars 1903).
Known distribution: Chiba Prefecture (Ikeya & Hanai 1982); Hiroshima Prefecture (Broodbakker 1988); Okayama Prefecture (Okubo 1974); Yamaguchi Prefecture (Broodbakker 1988). Elsewhere, China (Sars 1903; Yu et al. 2005; Zhai & Zhao 2014); Far-East Russia (Zenina & Schornikov, 2008).
Notes: See below for Ilyocypris dentifera.

References:
Broodbakker, N. W. 1988. Ecology and distribution of groundwater Crustacea and freshwater Ostracoda in SW Honshu and the Nansei Islands, Japan. Verlagen en Technische Gegevens Institute voor Taxonomische Zoologie, 53, 1-21.

Ikeya, N. & Hanai, T. 1982. Ecology of Recent ostracods in the Hamana-ko region, the Pacific coast of Japan. University Museum of the University of Tokyo, Bulletin 20, 15-59.

Okubo, I. 1974b. Freshwater Ostracoda from Japan, XI. Ilyocypris angulata Sars, 1903. The Research Bulletin of Okayama Shujitsu Junior College, 4, 46-50.

Sars, G.O. 1903. Fresh-water Entomostraca from China and Sumatra. Archiv for Mathematik og Naturvidenskab, 25, 3-44.

Victor, R. and Fernando, C. H. 1981. Ilyocypris dentifera Sars, 1903 versus Ilyocypris angulata Sars, 1903. A taxonomic study of two species of Ilyocypris Brady and Norman, 1889 (Crustacea, Ostracoda) described from China. Canadian Journal of Zoology, 59, 1103-1110.

Yu, N., Zhao, Q., Schornikov, E.L., & Chen, L. 2005. Recent Ostracods from the Taihu Lake. Acta Micropalaeontologica Sinica, 22, 143-151. [Chinese with English abstract].

Zenina, M. A., and E. I. Schornikov. 2008. Ostracod assemblages of the freshened part of Amursky Bay and lower reaches of Razdolnaya River (Sea of Japan), pp. 156-185. In, K. A. Lutaenko and M. A. Vaschenko (eds.), Ecological Studies and the State of the Razdolnaya River (Sea of Japan). Vol. 1. DalĠnauka, Vladivostok.

Zhai, D. & Zhao, W. 2014. On some recent non-marine ostracods from northern China, with description of one new species. Crustaceana, 87, 985-1026.


2. Ilyocypris dentifera Sars, 1903

Figures in: Sars 1903 (carapace and caudal ramus); Victor & Fernando 1981 (carapace and and parts of appendages); Okubo 2004 (carapace, sixth limb, Zenker organ, male sexual organ, but see notes).
Habitat: Generally considered a freshwater form, typical of rice fields, but Nakao & Tsukagoshi (2002) reported this species from a brackish estuary with a salinity of 21o/oo.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Sexual.
Known distribution: Chiba Prefecture (Nakao & Tsukagoshi 2002); Fukuoka Prefecture (Okubo 1990); Kagoshima Prefecture (Broodbakker 1988); Ryukyu Islands (Broodbakker 1988; Okubo 1990); Tokushima Prefecture (Okubo 1990); Shizuoka Prefecture (Tanaka et al 2015). Elsewhere, Korea (Kim & Min 1991); China (Sars 1903); Taiwan (Yu et al. 2009, citing grey literature); Philippines (Victor & Fernando 1980).
Notes: Ilyocypris dentifera and Ilyocypris angulata were both originally described by Sars (1903). Later, Victor & Fernando (1981) considered these species to be synonyms, an opinion that was followed by some authors (e.g. Martens 1991; Okubo 2004; Sari et al. 2012), but not others (e.g. Okubo 1990; Martens & Savatenalinton 2011; Karanovic & Lee 2013). It is not clear if figures in Okubo 2004 relate to I. dentifera or I. angulata.

References:
Broodbakker, N. W. 1988. Ecology and distribution of groundwater Crustacea and freshwater Ostracoda in SW Honshu and the Nansei Islands, Japan. Verlagen en Technische Gegevens Institute voor Taxonomische Zoologie, 53, 1-21.

Karanovic, I. & Lee, W. 2013. On the genus Ilyocypris, with a description of one new species from Korea and the first report of males of I. bradyi (Crustacea: Ostracoda: Podocopida). Proceedings of the Biological Society of Washington, 126, 39-71.

Kim, W. & Min, G.S. 1991. Redescription of four Recent freshwater ostracods (Crustacea: Ostracoda) from Korea. Korean Journal of Zoology, 34, 307-322.

Martens, K. 1991. On a small collection of non-marine ostracods from Mongolia, with the description of a new species (Crustacea, Ostracoda). Miscellanea Zoologica Hungarica, 6, 53-60.

Martens, K. & Savatenalinton, S. 2011. A subjective checklist of the Recent, free-living, non-marine Ostracoda (Crustacea). Zootaxa, 2855, 1-79.

Nakao, Y. & Tsukagoshi, A. 2002. Brackish-water Ostracoda (Crustacea) from the Obtsu River Estuary, Central Japan. Species Diversity, 7, 67-115.

Okubo, I. 1990. Sixteen species of freshwater Ostracoda from Japan. Bulletin of the Biogeographical Society of Japan, 45, 39-50.

Okubo, I. 2004. Nihon tansui san kaimijinko rui ni tsuite. Kabushikigaisha Sanmon Insatsusho, Okayama, Japan, 72pp. [In Japanese, privately published].

Sari, N., Külköylüoglu, O. & Akdemir, D. 2012. First record and detailed description of the male of Ilyocypris inermis Kaufmann, 1900 (Crustacea, Ostracoda). Turkish Journal of Zoology, 36, 484-495.

Sars, G.O. 1903. Fresh-water Entomostraca from China and Sumatra. Archiv for Mathematik og Naturvidenskab, 25, 3-44.

Tanaka, H., Kotorii, H., Yokozawa, K., Wakabayashi, F., Kimoto, K. & Sano, K. 2015. Distribution and occurrence of freshwater Ostracoda (Crustacea) from southwest region of Mt. Fuji. TAXA, Proceedings of the Japanese Society of Systematic Zoology, 38, 26-41. [In Japanese with English abstract.]

Victor, R. and Fernando, C. H. 1980. Freshwater Ostracoda from the ricefields of South East Asia. Tropical Ecology & Development, 1980, 957-970.

Victor, R. and Fernando, C. H. 1981. Ilyocypris dentifera Sars, 1903 versus Ilyocypris angulata Sars, 1903. A taxonomic study of two species of Ilyocypris Brady and Norman, 1889 (Crustacea, Ostracoda) described from China. Canadian Journal of Zoology, 59, 1103-1110.

Yu, N., Zhao, Q., Li, E., Chen, S. & Chen, L. 2009. An updated and annotated checklist of recent nonmarine ostracods from China. Zootaxa, 2067, 29-50.


3. Ilyocypris japonica Okubo, 1990


Right side view of a female Ilyocypris japonica, length about 0.95 mm.



External view of male left valve of Ilyocypris japonica, length 784 microns.



External view of male right valve of Ilyocypris japonica, length 769 microns.



The male sexual organ of Ilyocypris japonica, length 204 microns.


Additional figures in: Okubo 1990 (carapace, male fifth limb palp, caudal ramus, male sexual organ), Okubo 2004 (carapace, sixth limb, Zenker organ, male sexual organ).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Sexual.
Known distribution: Shiga Prefecture, Gumma Prefecture, Japan (Okubo 1990).

References:
Okubo, I. 1990. Sixteen species of freshwater Ostracoda from Japan. Bulletin of the Biogeographical Society of Japan, 45, 39-50.

Okubo, I. 2004. Nihon tansui san kaimijinko rui ni tsuite. Kabushikigaisha Sanmon Insatsusho, Okayama, Japan, 72pp. [In Japanese, privately published].



4. Ilyocypris nipponica Okubo, 2004 nomen nudum


Right side view of a female Ilyocypris nipponica, length about 0.85 mm.



External view of female left valve of Ilyocypris nipponica, length 875 microns.



External view of female right valve of Ilyocypris nipponica, length 847 microns.



The male sexual organ of Ilyocypris nipponica, length 226 microns.


Additional figures in: Okubo 2004 (carapace, sixth limb, Zenker organ, male sexual organ).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Sexual.
Known distribution: Shiga Prefecture (Okubo 2004).
Notes: As there was no designation of type material, and no information as to where the specimens are deposited (contravening sections 16.4.1 and 16.4.2 of the ICZN code), this is not a valid species. Only known from Japan.

References:
Okubo, I. 2004. Nihon tansui san kaimijinko rui ni tsuite. Kabushikigaisha Sanmon Insatsusho, Okayama, Japan, 72pp. [In Japanese, privately published].



5. Ilyocypris salebrosa Stepanaitys, 1960


Right side view of a female Ilyocypris salebrosa, length about 0.95 mm.



External view of female left valve of Ilyocypris salebrosa, length 964 microns.



External view of female right valve of Ilyocypris salebrosa, length 962 microns.



The male sexual organ of Ilyocypris salebrosa, length 209 microns.


Additional figures in: Smith et al 2011 (carapace and appendages).
Habitat: Lake Biwa, recorded from 5.5 to 16 m depth (Smith et al. 2011).
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Sexual in Lake Biwa. Males have not be reported from other areas.
Known distribution: Shiga Prefecture (Smith et al. 2011), Okinawa (Schornikov 2004). Outside of Japan reported from China (Mischke 2001), Turkey (Özulug 2005), Italy (Rossetti 2006), and Canada (Delorme 1970 as Pelocypris alatobulbosa).

References:
Delorme, L.D. 1970. Freshwater ostracodes of Canada. Part IV. Families Ilyocyprididae, Notodromadidae, Darwinulidae, Cytherideidae, and Entocytheridae. Canadian Journal of Zoology, 48, 1251-1259.

Mischke, S. 2001. Mid and Late Holocene palaeoenvironment of the lakes Eastern Juyanze and Sogo Nur in NW China, based on ostracod species assemblages and shell chemistry. Berliner Geowissenschaftliche Abhandlungen E 35, 1-131.

Özulug, O. 2005. Living specimens of Ilyocypris salebrosa Stepanaitys, 1959 (Crustacea: Ostaracoda) from Thrace, Turkey. Zoology in the Middle East, 34, 114-116.

Rossetti, G., Martens, K., Meisch, C., Tavernelli, S. & Pieri, V. 2006. Small is beautiful: diversity of freshwater ostracods (Crustacea, Ostracoda) in marginal habitats of the province of Parma (Northern Italy). Journal of Limnology, 65, 121-131.

Schornikov, E. 2004. Crustacea: Ostracoda. In: Tyurin, A.N. & Drozdov, A.L. (Eds), Far-Eastern Marine Biospherical Reserve. Biota. V. 2, Vladivostok, pp. 458-465. [In Russian].

Smith, R. J., Janz, H. & Okubo, I. 2011. Recent Cyprididae and Ilyocyprididae (Crustacea: Ostracoda) from Lake Biwa, Japan, including a summary of the lake's ostracod fauna. Zootaxa, 2874, 1-37.


Key charactersIlyocypris angulataIlyocypris dentiferaIlyocypris japonica Ilyocypris nipponica Ilyocypris salebrosa
Carapace - ventral valve overlapLeft valve overlaps right along ventral margin
Carapace - margin structure - septaNo septa present
Carapace - margin structure - ridges on inner calcified lamellaNo ridges
Carapace - dorsal view - female with brood pouchBrood pouch not visible
Carapace - lateral view - ventral marginVentral margin approximately straight to concave
Carapace - lateral view - valve heightLeft and right valves similar height
Carapace - internal viewAnterior calcified inner lamella wider than posterior one
Carapace - ornamentation - denticlesSmall denticles near ventral margin of valves No denticles near ventral marginSmall denticles near ventral margin of valves
Carapace - ornamentation - sulcusSulcus present near dorsal margin
Carapace - ornamentation - surfaceSurface pitted
Carapace - width/length ratio (w/l)Less than 0.4 (slender species)
Antennule - segmentsSeven moveable segments
Antennule - Rome organNo Rome organ
Antenna - exopoditeExopodite reduced to small segment
Antenna - swimming setaeSwimming setae very long, reaching well beyond end of claws Swimming setae long, reaching to about end of claws
Fifth limb - morphologyMaxilliped; Male palps with moveable terminal hooks
Sixth limb - segmentsFour segments Five segmentsFour segments Five segments
Sixth limb - setae on first segmentOne seta
Sixth limb - h3 seta on final segmentH3 seta short; much shorter than half length of claw
Seventh LimbCleaning limb, with three setae at end
Seventh Limb - segmentsFour segments
Seventh Limb - first segmentOne setae
Caudal ramusElongate ramus with two claws and two setae
Caudal ramus - attachmentWith no loops