at the Lake Biwa Museum, Japan

Robin James Smith

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Genus Cypridopsis Brady, 1867

Superfamily: Cypridoidea Baird, 1845
Family: Cyprididae Baird, 1845
Subfamily: Cypridopsinae Kaufmann, 1900

Three species have been reported from Japan:

1. Cypridopsis nigrovittata Okubo, 1990

Figures in: Okubo 1990 (carapace and caudal ramus); Okubo 2004 (carapace).
Habitat: Irrigations ponds and rice fields (Okubo 2004).
Mode of life: Nektobenthic (swimmer).
Reproductive mode: Asexual.
Known distribution: Okayama Prefecture (Okubo 1990).

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].

2. Cypridopsis uenoi Brehm, 1933

Figures in: Ueno 1965 (carapace, antenna, sixth limb and caudal ramus).
Habitat: Pools and rice fields.
Mode of Life: Nektobenthic (swimmer).
Reproductive Mode: Asexual?
Distribution: Nagano Prefecture (Brehm 1933), throughout Honshu (Ueno 1965).
Remarks: This species was last reported by Ueno (in Ueno & Hanai 1965), who stated it was found in rice fields and pools throughout Honshu, the main island of Japan. The type specimens are lost (McKenzie, 1972).

Brehm, V. 1933. Einige japanische Ostracoden. Transactions of the Natural History Society of Formosa, 23, 297-298.

McKenzie, K. G. 1972. Results of the speleological survey in South Korea 1966. XXII. Subterranean Ostracoda from South Korea. Bulletin of the National Science Museum, Tokyo, 15, 155-166.

Ueno, M. & T. Hanai. 1965. Ostracoda. In K. Okada et al. New illustrated encyclopedia of the fauna of Japan (Vol. 11). Hokuryukan, Tokyo, p. 453-456, figs. 416-427 (in Japanese).

3. Cypridopsis vidua (O. F. Müller, 1776)

Dorsal view of a female Cypridopsis vidua, length 0.6 mm. Anterior to the right. The patches of colouration are very variable, ranging from dark purple/black through to light green. Specimens with no colouration are also known.

External view of female left valve of Cypridopsis vidua, length 645 microns. The surface of the valves are often pitted (punctate) and covered with stiff setae.

External view of female right valve of Cypridopsis vidua, length 640 microns.

Additional figures in: Meisch 2000 (carapace and appendages); Okubo 2004 (carapace); Smith et al. 2011 (carapace).
Habitat: Found in a wide variety of habitats. In Japan found in lakes, ponds, and rice fields.
Mode of Life: Nektobenthic (swimmer).
Reproductive Mode: Asexual, males unknown (although see Meisch 2000, p. 377).
Distribution: Shiga Prefecture (Smith et al. 2011), Shizuoka Prefecture (Tanaka et al. 2015). Elsewhere found globally, a cosmopolitan species (Meisch 2000).

Meisch, C. 2000. Freshwater Ostracoda of Western and Central Europe. In: Schwoerbel, J., Zwick, P., (Eds.), Süßwasserfauna von Mitteleuropa 8/3. Spektrum Akademischer Verlag, Heidelberg, Berlin 522 pp.

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

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.

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.]

Key characters Cypridopsis species
Carapace - ventral valve overlapLeft valve overlaps right along ventral margin
Carapace - margin structure - septaNo septa present
Carapace - margin structure - ridges on inner calcified lamellaOn left valve*
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 - denticlesNo denticles near ventral margin
Carapace - ornamentation - sulcusNo sulcus
Carapace - ornamentation - surfaceSurface pitted
Carapace - width/length ratio (w/l)Greater than 0.7 (rounded species)
Antennule - segmentsSeven moveable segments
Antennule - Rome organRome organ present
Antenna - exopoditeExopodite reduced to small segment
Antenna - swimming setaeSwimming setae long, reaching to about end of claws
Fifth limb - morphologyMaxilliped
Sixth limb - segmentsFive 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 a pincer at end
Seventh Limb - segmentsThree segments
Seventh Limb - first segmentThree setae
Caudal ramusReduced ramus with two setae
Caudal ramus - attachmentWith no caudal ramus attachment

* The left valve has a double folded inner list on the posterior calcified inner lamella.