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Gamophyceae: Zygnematales: Desmidiaceae

 Cosmarium depressum
var. planctonicum Reverdin

Cosmarium depressum Species [ var. depressum ]: Cell body small in size, wider than length, 33-50 μm long, (36.5-47.5)-50 μm wide, isthmus 10-15 μm wide; semicells depressed ellipsoid, with slightly flattened apex, side view circular, apical view elliptical, with a single pyrenoid.
[ var. minor W. et G.S. West ]: Cell body smaller than var. depressum, 21-28 μm long, 21-25.3 μm wide, isthmus 4.3-8.4 μm wide; semicells elliptical diamond-shaped.
[ var. achondrum (Boldt) W. et G.S. West ]: Cell body 36-51 μm long, 40-52 μm wide, L/W=1.0; isthmus 11-17 μm wide; semicells hexagonal ellipsoid, apex broad, flattened (Illustrations of The Japanese Fresh-water Algae, 1977).
Similar species -- >> C. bioculatum; C. contractum;

Cosmarium depressum var. planctonicum Reverdin ?, cell body 22 μm long, 19 μm wide, L/W=1.2, isthmus 6 μm wide, x 640, No. 2, Iroha-numa (marsh/bog), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii
scale 31 μm scale 63 μm scale 94 μm; x 640
Cosmarium

Images of collecting locality: No. 2, Iroha-numa (marsh/bog), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii

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