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Gamophyceae: Zygnematales: Desmidiaceae

 Cosmarium quadrum
Lundell var. quadrum

Cosmarium quadrum 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 rectangular, 53-90 μm long, 47.6-85 μm wide; isthmus 19-30 μm wide; semicells subrectangular, with rounded corners; side view nearly circular; apical view elongated ellipsoidal; marginal granules 34-37 in number (Illustrations of the Japanese fresh-water algae, 1977).

Cosmarium quadrum Lundell var. quadrum (or Cosmarium margaritatum (Lundell) Roy et Bisset var. margaritatum ?), outline shape similar to Cosmarium latifrons Lundell but larger, cell body 85 μm long, 64 μm wide, L/W=1.3, isthmus 23 μm wide, x 640, Ushiku-numa-Mizube-koen (Ushiku-numa pondside park), Ryugasaki city, Ibaraki Pref., Japan, March 27, 2007 by Y. Tsukii
scale 31 μm scale 63 μm scale 94 μm; x 640
Cosmarium quadrum Cosmarium quadrum
Cell body 100 μm long, 71 μm wide, L/W=1.4, isthmus 27 μm wide, x 640
Cosmarium quadrum Cosmarium quadrum Cosmarium quadrum
Cell body 88 μm long, 63 μm wide, L/W=1.4, isthmus 23 μm wide, x 640
Cosmarium quadrum Cosmarium quadrum Cosmarium quadrum Cosmarium quadrum

Images of collecting locality: Ushiku-numa-Mizube-koen (Ushiku-numa pondside park), Ryugasaki city, Ibaraki Pref., Japan, March 27, 2007 by Y. Tsukii

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