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 with a short projection at one end; terminus of the projection slightly swelled; daughter cells attached at opposite end of their mother cell (Illustrations of Japanese fresh-water algae, 1977).

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O. arbuscula up to 80 x 4.7 μm Toneri Park Tokyo, 2001	O. arbuscula 70 x 4.5 μm Akigase Park Saitama, 2002	O. arbuscula stock Sua-2 10-52 x 4.5 μm Akigase Park Saitama, 2002	O. arbuscula stock Sua-2 10-80 x 4.5 μm Akigase Park Saitama, 2002
O. arbuscula or O. gracilipes ? 10-80 x 4.5 μm Shimo-muneoka Shiki Saitama, 2004	O. arbuscula or O. gracilipes ? stock Sssm-1 Shimo-muneoka Shiki Saitama, 2004	O. arbuscula ? 110 x 7 μm near Town Hall near Town Hall Saitama, 2004

Similar genus -->> Centritractus

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