OSTRACOD RESEARCH

at the Lake Biwa Museum, Japan


Robin James Smith

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Genus Chrissia Hartmann, 1957

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

Two species have been reported from Japan:

1. Chrissia formosa (Klie, 1938)


Left side view of a female Chrissia formosa, length about 1.5 mm.



External view of a female left valve of Chrissia formosa, length 1566 microns.


External view of a female right valve of Chrissia formosa, length 1553 microns.

Additional figures in: Klie 1938 (carapace and caudal ramus); Victor & Fernando 1981 (carapace and appendages); Okubo 2004 (carapace and caudal ramus); Smith et al. 2011 (carapace).
Habitat: Paddy fields (Okubo 2004), Lake Biwa (Smith et al. 2011). Elsewhere reported from a freshwater lagoon (Victor & Fernando 1981).
Mode of life: Nektobenthic (swimmer)
Reproductive mode: Asexual, males unknown.
Known distribution: Shiga Prefecture (Smith et al. 2011), Shizouka Prefecture (Kato 1944). Elsewhere known from Taiwan (Klie 1938), and the Philippines (Victor & Fernando 1981).

References:
Kato, K. 1944. Stenocypris from Izu. Zoology Magazine, 56, 57.

Klie, W. 1938. Ostracoden aus Formosa. Bulletin of the Biogeographical Society of Japan, 8, 21-33.

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.

Victor, R. & Fernando, C.H. 1981. Freshwater Ostracoda of the genera Chrissia Hartmann, 1957 and Stenocypris Sars, 1889 from Malaysia, Indonesia and the Philippines. Mitteilungen aus dem Hamburgischen Zoologischen Museum und Institut, 78, 151-168.


2. Chrissia vittata Okubo, 1974

Figures in: Okubo 1974 (carapace and appendages); Okubo 2004 (carapace).
Habitat: Rice fields (Okubo 1974); pond, field (Broodbakker 1988).
Mode of life: Nektobenthic (swimmer)
Reproductive mode: Asexual, males unknown.
Known distribution: Kagoshima Prefecture (Okubo 1974; 2004; Broodbakker 1988); Okinawa (Broodbakker 1988). Currently only known from Japan.

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. 1974. Chrissia vittata sp. nov. from Japan (Ostracoda, Cyprididae). Proceedings of the Japanese Society of Systematic Zoology, 10, 1-9.

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


Key characters Chrissia formosa & Chrissia vittata
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 - denticlesNo denticles near ventral margin
Carapace - ornamentation - sulcusNo sulcus
Carapace - ornamentation - surfaceSurface smooth
Carapace - width/length ratio (w/l)Less than 0.4 (slender 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 segmentTwo setae
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 ramusElongate ramus with two claws and one seta
Caudal ramus - attachmentTriangular loop at ventral end