Lake Biwa Museum

**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; Zhai & Zhao 2014 ; Smith et al. 2019.; Habitat: Rivers, lakes, pools and puddles.; Mode of life: Nektobenthic (swimmer).; Reproduction mode: Sexual.; Known distribution: Japan (?) (Broodbakker 1988; Ikeya & Hanai 1982; Hayashi et al. 2009), China (Sars 1903; Yu et al. 2005; Zhai & Zhao 2014).; Notes: There are unconfirmed reports of this species from Japan, but they could be misidentifications of tuberculated forms of I. 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.; ⚬ Hayashi, N., Ohuchi, T. & Miyata, N. 2009. Planktonic biota occurring in rice fields in Japan. Journal of Natural History Museum and Institute, Chiba, 10, 71-79. [In Japanese, with English abstract]; ⚬ 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.; ⚬ Sars, G.O. 1903. Fresh-water Entomostraca from China and Sumatra. Archiv for Mathematik og Naturvidenskab, 25, 3-44.; ⚬ Smith, R. J., Zhai, D. & Chang, C. Y. 2019. Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields; description of one new species, and redescriptions of Ilyocypris dentifera Sars, 1903 and Ilyocypris japonica Okubo, 1990. Zootaxa, 4652, 56-92.; ⚬ 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].; ⚬ 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; Victor & Fernando 1981; Smith et al. 2019.; Habitat: Often found in ricefields, but also in temporary pools.; Mode of life: Nektobenthic (swimmer).; Reproduction mode: Sexual.; Known distribution: 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 (Smith et al. 2019); China (Sars 1903; Yu 2014); Taiwan (Yu et al. 2009, citing grey literature); Philippines (Victor & Fernando 1980).
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.; ⚬ Okubo, I. 1990. Sixteen species of freshwater Ostracoda from Japan. Bulletin of the Biogeographical Society of Japan, 45, 39-50.; ⚬ Sars, G.O. 1903. Fresh-water Entomostraca from China and Sumatra. Archiv for Mathematik og Naturvidenskab, 25, 3-44.; ⚬ Smith, R. J., Zhai, D. & Chang, C. Y. 2019. Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields; description of one new species, and redescriptions of Ilyocypris dentifera Sars, 1903 and Ilyocypris japonica Okubo, 1990. Zootaxa, 4652, 56-92.; ⚬ 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.; ⚬ Yu, N. 2014. Non-marine Ostracoda from China. Shanghai Educational Publishing House, Shanghai, 283 pp. [in Chinese].; ⚬ 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 incus Smith et al., 2019

Figures in: Smith et al. 2019.; Habitat: Ricefields; Mode of life: Nektobenthic (swimmer).; Reproduction mode: Sexual.; Known distribution: Okayama Prefecture, Japan. Elsewhere Korea (Smith et al. 2019).
References:: ⚬ Smith, R. J., Zhai, D. & Chang, C. Y. 2019. Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields; description of one new species, and redescriptions of Ilyocypris dentifera Sars, 1903 and Ilyocypris japonica Okubo, 1990. Zootaxa, 4652, 56-92.

4. Ilyocypris japonica Okubo, 1990

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, Okubo 2004; Smith et al. 2019.; Habitat: Rice fields.; Mode of life: Nektobenthic (swimmer).; Reproduction mode: Sexual.; Known distribution: Shiga Prefecture, Gumma Prefecture, Japan (Okubo 1990). Elsewhere, Korea (Smith et al. 2019).
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].; ⚬ Smith, R. J., Zhai, D. & Chang, C. Y. 2019. Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields; description of one new species, and redescriptions of Ilyocypris dentifera Sars, 1903 and Ilyocypris japonica Okubo, 1990. Zootaxa, 4652, 56-92.

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.

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.