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 30-68 μm long, 26-34(-38) μm wide; conjugation tubes formed by both gametangial cells; fertile cells cylindrical or inflated on the conjugating side; zygospores broad ellipsoidal, 32-38 μm in diam., 32-43 μm long; medial spore wall golden yellow, with small pores 4-5 μm in diam. 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