OSTRACOD RESEARCH

at the Lake Biwa Museum, Japan


Robin James Smith

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Genus Pseudocandona Kaufmann, 1900

Superfamily: Cypridoidea Baird, 1845
Family: Candonidae Kaufmann, 1900
Subfamily: Candoninae Kaufmann, 1900

Six species have been reported from Japan:

1. Pseudocandona abei Smith & Janz, 2008


Left side view of a female Pseudocandona abei, length about 0.7 mm.


External view of a female left valve of Pseudocandona abei, length 698 microns.


External view of a female right valve of Pseudocandona abei, length 673 microns.

Additional figures in: Smith & Janz 2008 (carapace and appendages).
Habitat: Shallow areas of Lake Biwa around willow tree root mats, streams, and marshy areas.
Mode of life: Benthic.
Reproductive mode: Asexual. Males unknown.
Known distribution: Shiga Prefecture and Ishikawa Prefecture, Japan (Smith & Janz 2008).

References:
Smith, R. J. & Janz, H. 2008. Recent species of the Family Candonidae (Ostracoda, Crustacea) from the ancient Lake Biwa, Central Japan. Journal of Natural History, 42, 2865-2922.


2. Pseudocandona atmeta Smith & Kamiya, 2015


Left side view of a female Pseudocandona atmeta, length about 1.2 mm.


External view of a male left valve of Pseudocandona atmeta, length 1227 microns.


External view of a male right valve of Pseudocandona atmeta, length 1202 microns.


Male sexual organ of Pseudocandona atmeta, length 439 microns.

Additional figures in: Smith & Kamiya 2015 (carapace and appendages).
Habitat: Boggy areas with reeds and grasses.
Mode of life: Benthic.
Reproductive mode: Sexual.
Known distribution: Aomori Prefecture, Japan.

Smith, R. J. & Kamiya, T. 2015. Four new species of the subfamily Candoninae (Crustacea, Ostracoda) from freshwater habitats in Japan. European Journal of Taxonomy, 136, 1-34.


3. Pseudocandona becca Smith & Kamiya, 2015


Left side view of a male Pseudocandona becca, length about 1.1 mm.


External view of a male left valve of Pseudocandona becca, length 1169 microns.


External view of a male right valve of Pseudocandona becca, length 1140 microns.


Male sexual organ Pseudocandona becca, length 376 microns.

Additional figures in: Smith & Kamiya 2015 (carapace and appendages).
Habitat: Interstitial in sand.
Mode of life: Benthic.
Reproductive mode: Sexual.
Known distribution: North-western part of Lake Biwa.

Smith, R. J. & Kamiya, T. 2015. Four new species of the subfamily Candoninae (Crustacea, Ostracoda) from freshwater habitats in Japan. European Journal of Taxonomy, 136, 1-34.


4. Pseudocandona falcula Smith & Kamiya, 2015


External view of a male left valve of Pseudocandona falcula, length 950 microns.


External view of a male right valve of Pseudocandona falcula, length 934 microns.


Male sexual organ Pseudocandona falcula, length 378 microns.

Additional figures in: Smith & Kamiya 2015 (carapace and appendages).
Habitat: Root mats of willow trees, and marshy areas.
Mode of life: Benthic.
Reproductive mode: Sexual.
Known distribution: Aomori Prefecture, and Lake Biwa, Shiga Prefecture.

Smith, R. J. & Kamiya, T. 2015. Four new species of the subfamily Candoninae (Crustacea, Ostracoda) from freshwater habitats in Japan. European Journal of Taxonomy, 136, 1-34.


5. Pseudocandona pratensis (Hartwig, 1901)

Figures in: Meisch 2000 (carapace and appendages), Karanovic 2013 (carapace and appendages, as Typhlocypris pratensis (Hartwig, 1901)), Tanaka et al. 2015 (carapace, male fifth limbs, seventh limb, hemipenis).
Habitat: In Japan reported from paddy fields (Tanaka et al. 2015). Elsewhere mainly found in temporary water bodies, but also ponds, lakes, rivers, brooks and springs (Meisch 2000).
Mode of life: Benthic.
Reproductive mode: Sexual.
Known distribution: Shizuoka Prefecture (Tanaka et al. 2015). Elsewhere known from Europe (Meisch 2000) and Korea (Karanovic 2013, as Typhlocypris pratensis ).

References:
Karanovic I. 2013. Earicandona, new genus and the first record of Typhlocypris pratensis (Crustacea, Ostracoda) from South Korea. Journal of Species Research, 2, 145-158.

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.

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.]


6. Pseudocandona tenuirostris Hiruta & Mawatari, 2013


Left side view of a male Pseudocandona tenuirostris, length about 1.1 mm.


Male sexual organ Pseudocandona tenuirostris, length 395 microns.

Additional figures in: Hiruta & Mawatari 2013 (carapace and appendages).
Habitat: Marshy areas.
Mode of life: Benthic.
Reproductive mode: Sexual.
Known distribution: Aomori Prefecture (Smith & Kamiya 2015), and Hokkaido (Matzke-Karasz et al. 2004 (as Pseudocandona rostrata); Hiruta & Mawatari 2013).

References:
Hiruta, S. F. & Mawatari, S. F. 2013. Ostracods (Crustacea) from Sarobetsu Marsh, northern Hokkaido, Japan: taxonomy and phenology with description of Pseudocandona tenuirostris sp. nov. Species Diversity, 18, 57-74.

Matzke-Karasz, R, Smith, R. J. & Homma, M. 2004. Cyclocypris diebeli Absolon, 1973 (Ostracoda, Crustacea), extinct in Europe, extant in Japan. Journal of Natural History, 38 (13), 1635 - 1663.

Smith, R. J. & Kamiya, T. 2015. Four new species of the subfamily Candoninae (Crustacea, Ostracoda) from freshwater habitats in Japan. European Journal of Taxonomy, 136, 1-34.


Key characters P. abei P. atmeta P. becca P. falcula P. pratensis P. tenuirostris
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)Between 0.4 and 0.7 (medium species)Less than 0.4 (slender species)Between 0.4 and 0.7 (medium species)
Antennule - segmentsSeven moveable segments
Antennule - Rome organNo Rome organ
Antenna - exopoditeExopodite reduced to small segment
Antenna - swimming setaeNo swimming setae present
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 Limb Cleaning limb, with three setae at end
Seventh Limb - segmentsFour segmentsFive segments
Seventh Limb - first segmentThree setae
Caudal ramusElongate ramus with two claws and two setae
Caudal ramus - attachmentWith no loops

* Pseudocandona atmeta has some very fine pits in the central area of the valves, which can be observed with scanning electron microscopy.