OSTRACOD RESEARCH

at the Lake Biwa Museum, Japan


Robin James Smith

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Subfamily Entocytherinae Hoff, 1942

Superfamily: Cytheroidea Baird, 1850
Family: Entocytheridae Hoff, 1942

Two species have been reported from Japan:

1. Ankylocythere sinuosa (Rioja, 1942)

Figures in: Hart & Hart 1974 (carapace and male sexual organ)
Habitat: Rivers
Mode of life: Commensal on the red swamp crayfish Procambarus clarkii, typically found on the gills.
Reproduction mode: Sexual.
Known distribution: Tokyo (Ohtaka et al. 2017). Elsewhere, western USA, Spain, England and the Czech Republic (see references in Ohtaka et al. 2017).
Notes: This is an invasive species in Japan, originating from the USA (Ohtaka et al. 2017).

2. Uncinocythere occidentalis (Kozloff & Whitman, 1954)


Right side view of a male (top) and female of Uncinocythere occidentalis, length 0.4 mm.

Additional figures in: Hart & Hart 1974 (carapace and male sexual organ); Smith & Kamiya 2001 (carapace and appendages).
Habitat: Lakes and rivers.
Mode of life: Commensal on the signal crayfish Pacifastacus leniusculus trowbridgii, typically found on the gills.
Reproduction mode: Sexual.
Known distribution: Hokkaido (Smith & Kamiya 2001). Elsewhere, western USA (Hart & Hart 1974), UK, Spain, France, the Netherlands and Germany (see references in Ohtaka et al. 2017).
Notes: This is an invasive species in Japan, originating from the USA (Smith & Kamiya 2001).

References:
Hart, D. G. & Hart, Jr., C. W. 1974. The ostracod family Entocytheridae. The Academy of Natural Sciences of Philadelphia, Monograph 18, 1-239.

Smith, R. J. & Kamiya, T. 2001. The first record of an entocytherid ostracod (Crustacea: Cytheroidea) from Japan. Benthos Research, 56 (2), 57-61.


Key characters Uncinocythere occidentalis
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 viewNo calcified inner lamella
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 absent
Antenna - exopoditeExopodite a spinneret seta
Antenna - swimming setaeNo swimming setae present
Fifth limb - morphologyWalking leg
Sixth limb - segmentsFour segments
Sixth limb - setae on first segmentOne seta
Sixth limb - h3 seta on final segmentNo h3 seta
Seventh LimbWalking leg, larger than sixth limb
Seventh Limb - segmentsFour segments
Seventh Limb - first segmentOne seta
Caudal ramusReduced to only one or two setae or absent
Caudal ramus - attachmentWith no caudal ramus attachment