Cosmarium impressulum. Notice semi-oblong semicells with some eight, rather faint, marginal undulations.
Cell dimensions (L x B): 20 x 14 µm

SEM image of C. impressulum. Notice asymmetrical cell shape (and faintly scrobiculate wall).


Desmid of the month
March 2023

Cosmarium impressulum

Cosmarium impressulum belongs to the problematic group of small-sized Cosmaria with a smooth cell wall. Semicells are semi-oblong in outline marked by some eight, rather faint undulations. Often, cell outline is not very symmetrical: undulations may differ in an irregular way in size and expression. In the Netherlands, C. impressulum is a fairly common species in various meso-eutrophic water bodies.

Two other cells of C. impressulum showing an irregular undulation of the cell outline.