Cells single. Most taxa slightly compressed, therefore elliptical in vertical view. Median incision is usually pronounced but unlike in Euastrum or Micrasterias cells are not lobed. Wall ornamentation varies greatly, ranging from smooth to punctate, scrobiculate or granulate. Large genus, probably in need of splitting.
Ecological preferences vary greatly, but unlike Euastrum or Micrasterias, many Cosmarium taxa occur in alkaline waters of higher trophic rank. Generally in the benthos and metaphyton, but some taxa are true plankters.
Estimated number of taxa in this genus: approx. 2,000
Cosmarium obtusatum |
Cosmarium botrytis |
Cosmarium depressum |
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