Species [ var. dianae ]: Cell body slightly curved, tapered toward both ends, truncated with slanted edges, small pores present at outside of both termini, inner side at center slightly convex, 150-380 μm long, 15-40 μm wide, L/W = 10-12; cell wall smooth; chloroplasts with 5-8 pyrenoids in each chloroplast (Illustrations of The Japanese Fresh-water Algae, 1977). Cell body 160-323 μm long, 20-28 μm wide, L/W=8.3-12; chloroplasts with about 6 laminae; semicells with 4-8 pyrenoids (Photomicrographs of the Freshwater Algae, vol. 6, 1987). [var. minus]: Cell body 140-150 μm long, 15 μm wide; (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Closterium dianae var. minus (Wille) Schröder ?, cell body 122 μm long, 11 μm wide, L/W=11.1, x 640, Iroha-numa (marsh/bog), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii
31 μm 63 μm 94 μm; x 640

Cell body 132 μm long, 11 μm wide, L/W=12.0, x 640

Images of collecting locality: No. 1, Iroha-numa (marsh/bog), Zao mountain, Yamagata city, Yamagata Pref., Japan, August 2, 2006 by Y. Tsukii