Genus: Colonies, 3-dimensional; cell body cylindrical or long spindle in shape, radially arranged by attaching at one end to each other (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Colonies of 8, 16, 32 cells; tapered at both ends; 20-25 μm long, 2-3 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

50 μm 100 μm 150 μm; x 400 : 31 μm 63 μm 94 μm; x 640

Actinastrum hantzschii Lagerheim var. hantzschii: Colonies of 4 or 8 cells; body spindle-shaped, truncated at both ends; 10-25 μm long, 3-6 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

* Actinastrum hantzschii Lagerheim var. fluviatile Shroeder: Colonies of 8, 16, 32 cells; tapered at both ends; 20-25 μm long, 2-3 μm wide (Illustrations of The Japanese Fresh-water Algae, 1977).

Actinastrum hantzschii Lagerheim var. curvatum Hortobagyi: Colonies of 8, 16, 32 cells; cellscrescent in shape with rounded ends; 18-25 μm long, 2.5-4 μm wide (Photomicrographs of the Freshwater Algae, 1996).

Actinastrum gracillimum G. M. Smith var. gracillimum: Colonies fo 8 or 16 cells; cells cylindrical, truncately rounded at both ends; 8-20 μm long, 1.5-3 μm wide (Photomicrographs of the Freshwater Algae, 1996).

Actinastrum raphidioides (Reinsch) Brunnthaler: Colonies fo 8 or 16 cells; cells long cylindrical, with tapered outer end and rounded basal end; 10-30 μm long, 2-5 μm wide, similar to A. hantzschii var. fluviatile (Photomicrographs of the Freshwater Algae, 1996).