Genus: Unicellular; planktonic; cell body elongated cylindroid, curved or twisted; both ends rounded, with spiny projections; cell wall not separated into two parts (compare to Centritractus); several chloroplasts plate-like, without pyrenoids (Guide book to the "Photomicrographs of the Freshwater Algae", 1998).
Species: Cell body 14-21 wide,
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Similar genus -->> Centritractus
O. bicuspidatum
or O. captatum ?
80 x 8 μm
Tane-ike
Togakushi highland
Nagano, 2005
O. bicuspidatum
or O. captatum ?
65 x 6 μm
Suiren-numa
Hakkoda mountain
Aomori, 2005
O. bicuspidatum
or O. captatum ?
220 x 9 μm
Kashibaru marsh 5
Karatsu
Saga, 2006
