OSTRACOD RESEARCH

at the Lake Biwa Museum, Japan


Robin James Smith

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Genus Hemicypris Sars, 1903

Superfamily: Cypridoidea Baird, 1845
Family: Cyprididae Baird, 1845
Subfamily: Cyprinotinae Bronshtein, 1947

Seven species have been reported from Japan:

1. Hemicypris kaufmanni (Vávra, 1906)

Figures in: Vávra 1906 (carapace and caudal ramus, as Cyprinotus (Hemicypris Sars G. O) kaufmanni).
Habitat: A stoup in a temple.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Asexual, males unknown.
Known distribution: Nagasaki Prefecture (Vávra 1906).
Notes: Only one record of this species exists. This species needs to be redescribed.

References:
Vávra, W. 1906. Ostracoden von Sumatra, Java, Siam, den Sandwich-Inseln und Japan. Zoologische Jahrbuecher Systematik, 23, 413-438, Pls. 24-25.


2. Hemicypris kawagaensis Okubo, 2004 nomen nudum

Figures in: Okubo 2004 (carapace).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Asexual, males unknown.
Known distribution: Kagawa 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. It needs to be redescribed.

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


3. Hemicypris megalops Sars, 1903

Figures in: Sars 1903 (carapace and caudal ramus); McKenzie 1966 (carapace, parts of antennule, maxilulla and caudal ramus); Battish 1981 (carapace, fifth limb, parts of maxillula, seventh limb and caudal ramus); Victor & Fernando 1981 (carapace and parts of appendages); Okubo & Ida 1989 (carapace, as Hemicypris sp. B); Okubo 1990 (carapace and caudal ramus, as Hemicypris kibiensis); Okubo 2004 (carapace).
Habitat: Rice fields.
Mode of Life: Nektobenthic (swimmer).
Reproduction Mode: Asexual, males unknown.
Distribution: Okayama Prefecture; Gunma Prefecture (Okubo and Ida 1989, as Hemicypris sp. B; Okubo 1990, as Hemicypris kibiensis sp. nov.) and Shizuoka Prefecture (Tanaka et al. 2015). Elsewhere, Indonesia (Sars 1903; Victor & Fernando 1981); Taiwan (Klie 1938); Malaysia (Victor & Fernando 1981); India (Jain 1977; Battish 1981); North-western Australia (McKenzie 1966).
Notes: The Australian record of this species was based on juvenile specimens (McKenzie 1966).

References:
Battish, S. K. 1981. Freshwater Ostracoda of the subfamily Cyprinotinae from Punjab, India, with the description of eight new species. Journal of Natural History, 15, 645-669.

Jain, S. P. 1977. Recent freshwater ostracodes from Chilka Lake area. Journal of the Palaeontological Society of India, 20, 356-359.

McKenzie, K. G. 1966. Freshwater Ostracoda from North-western Australia. Australian Journal of Marine and Freshwater Research, 17, 259-279.

Okubo, I. 1990a. Seven new species of freshwater Ostracoda from Japan. Researches on Crustacea, 19, 1-12.

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

Okubo, I. & Ida, K. 1989. Freshwater Ostracoda from Gunma Prefecture, Japan (In Japanese). Bulletin of the Biogeographical Society of Japan, 44, 105-107.

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

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. & Fernando, C. H. 1981. Freshwater ostracods (Crustacea: Ostracoda) of the subfamily Cyprinotinae Bronstein, 1947 from Malaysia, Indonesia and the Philippines. Hydrobiologia, 83, 11-27.


4. Hemicypris mizunoi Okubo, 1990

Figures in: Okubo 1990 (carapace and caudal ramus); Okubo 2004 (carapace).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Asexual, males unknown.
Known distribution: Okayama Prefecture (Okubo 1990). Elsewhere, Thailand (Savatenalinton & Martens 2008).
Notes: Japanese specimens were first described as a new species, Hemicypris mizunoi Okubo, 1990, but were later considered to be a junior synonym of Hemicypris pyxidata (Moniez, 1892) by Okubo (2004). However, Savatenalinton & Martens (2008) considered H. mizunoi to differ from H. pyxidata, and re-described H. mizunoi using specimens collected from Thailand.

References:
Okubo, I. 1990. Seven new species of freshwater Ostracoda from Japan. Researches on Crustacea, 19, 1-12.

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

Savatenalinton, S. & Martens, K. 2008. Redescription of Hemicypris mizunoi Okubo, 1990 (Crustacea, Ostracoda) from Thailand, with a reassessment of the validity of the genera Hemicypris and Heterocypris. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Biologie, 78, 17-27.


5. Hemicypris okayamenesis Okubo, 2004 nomen nudum

Figures in: Okubo 2004 (carapace).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Asexual, males unknown.
Known distribution: Okayama 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. It needs to be redescribed.

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


6. Hemicypris ovata Sars, 1903

Figures in: Okubo 1990 (carapace and caudal ramus, as Hemicypris nipponica); Okubo 2004 (carapace).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Asexual, males unknown.
Known distribution: Okayama Prefecture and Gunma Prefecture (Okubo 1990, as Hemicypris nipponica).
Notes: See Hemicypris vulgaris below.

References:
Okubo, I. 1990. Seven new species of freshwater Ostracoda from Japan. Researches on Crustacea, 19, 1-12.

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


7. Hemicypris vulgaris Okubo, 1990


Left side view of a female Hemicpris sp., length 1.2 mm. Hemicypris is one of the few genera where the right valve overlaps the left ventrally (usually the opposite overlap occurs).



External view of a left valve of a female Hemicpris vulgaris. Length 1165 microns.



External view of a right valve of a female Hemicpris vulgaris. Length 1189 microns.


Additional figures in: Okubo 1990 (carapace and caudal ramus); Okubo 2004 (carapace).
Habitat: Rice fields.
Mode of life: Nektobenthic (swimmer).
Reproduction mode: Asexual, males unknown.
Known distribution: Okayama Prefecture and Gunma Prefecture (Okubo 1990).
Notes: Hemicypris vulgaris and Hemicypris ovata figured by Okubo 1990, 2004 are very similar. There are very small differences in colouration and size of the carapaces and relative lengths of the claws and setae on the caudal ramus. Japanese specimens of both species need to be reinvestigated.

References:
Okubo, I. 1990. Seven new species of freshwater Ostracoda from Japan. Researches on Crustacea, 19, 1-12.

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


Key characters Hemicypris species
Carapace - ventral valve overlapRight valve overlaps left 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
Carapace - ornamentation - sulcusNo sulcus
Carapace - ornamentation - surface Surface smooth
Carapace - width/length ratio (w/l)Between 0.4 and 0.7 (medium 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 ramusElongate ramus with two claws and two setae
Caudal ramus - attachmentWith no loops