I find Asterococcus limneticus very frequently but only in the Simmelried. The colonies are quite conspicuous because the cells are comparatively large (about 20 µm) and they are clearly separated from each other in the mucilage.

The cells have two distinct contractile vacuoles in the periphery, which are always closely adjacent (s. fig. 3 b). They usually pulsate alternately. The chloroplast is star-shaped and columnar arms arise from the center and extend to the cell wall. If the focal plane is on the periphery of the cells, these “columns” become visible in apical view (s. fig. 2 a and 3 a). In the center of the chloroplast there is a clearly visible pyrenoid, which is often covered by starch grains (s. fig. 4).

The very similar species Asterococcus superbus differs from Asterococcus limneticus only by the clearly layered mucilage. The mucilage layers build up concentrically. In Asterococcus limneticus, only young colonies show a hint of layering, which disappears in older colonies.