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Gamophyceae: Zygnematales: Desmidiaceae

Cosmarium pseudarctoum
Nordstedt var. var. perminutum (G.S. West) Ström
= Actinotaenium pseudarctoum Nordstedt var. var. perminutum (G.S. West) Ström

Cosmarium pseudarctoum Genus: Unicellular; variable in shape; a constriction at the center of the cell body; mostly longer than wide; flattened; each semicell hemispherical, spherical, ellipsoidal, rectangular, pyramidal or kidney-shaped; no apical indentation (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: Cell body small, 16-(17-26.5) μm long, (10.5-14)-18 μm wide, isthmus 10-(10.5-14)-17 μm, L/W=1.25-1.5; semicells nearly spherical or inverted broad ovoidal; both ends broader than the center; apex slightly flat; cell wall smooth;
var. perminutum: 9-13.5 μm long, 5.6-8.5 μm wide, isthmus 6-7 μm, L/W=2; semicells inverted ovoidal; apex rounded (Illustrations of The Japanese Fresh-water Algae, 1977).


Cosmarium pseudarctoum Nordstedt var. perminutum (G.S. West) Ström, cell body 16 μm long, 8.5 μm wide, x 640, Sendabori, Matsudo city, Chiba Pref., Japan, January 2002 by Y. Tsukii
scale 31 μm scale 63 μm scale 94 μm; x 640
Cosmarium pseudarctoum Cosmarium pseudarctoum Cosmarium pseudarctoum Cosmarium pseudarctoum

Cosmarium pseudarctoum, cell body μm long, μm wide, x 640, Sendabori, Matsudo city, Chiba Pref., Japan, January 2002 by Y. Tsukii
scale 31 μm scale 63 μm scale 94 μm; x 640
Cosmarium pseudarctoum Cosmarium pseudarctoum Cosmarium pseudarctoum


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