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Gamophyceae: Zygnematales: Desmidiaceae

 Cosmarium depressum
(Nägeli) Lundell var. depressum

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 (Nägeli) Lundell var. depressum or C. contractum var. ellipsoideum ?, cell body 38 μm long, 30 μm wide, L/W=1.3, isthmus 8 μm wide, x 640, Aka-ike (pond), Madarao highland (Niigata & Nagano Pref.), Myoko city (formerly Myoko village), Niigata Pref., Japan, June 17, 2006 by Y. Tsukii
scale 31 μm scale 63 μm scale 94 μm; x 640
Cosmarium Cosmarium

Images of collecting locality: Aka-ike (pond), Madarao highland (Niigata & Nagano Pref.), Myoko city (formerly Myoko village), Niigata Pref., Japan, June 17, 2006 by Y. Tsukii

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