Genus: Filament without branching; cell body cylindrical; two chloroplasts star-shaped;
tubes formed (or cell body fused) at conjugation; zygospore spherical or broad ellipsoidal formed within female gametangium
(Guide book to the "Photomicrographs of the Freshwater Algae", 1998).
Species: Cell body 30-73 μm long, 16-20 μm wide; conjugation tubes formed by both gametangial cells; fertile cells inflated on the conjugating side; zygospores spherical or nearly spherical, 36-46 μm in diam., 34-45 μm long; medial spore wall yellowish brown, with small pores 3-4 μm in diam. arranging at 2.5-4 μm intervals at maturity (Illustrations of The Japanese Fresh-water Algae, 1977).
Zygnema excompressum Transeau: vegetative cells 32-80 μm long, 23-26 μm diam., 2 chloroplasts in each cell