Cosmarium anceps. Notice shallow cell sinus and trapeziform semicells with concave sides.

Cell dimensions (L x B): 30 x 16 µm

Cosmarium anceps var. borgei. Notice semicells with undulate lateral sides.

Image © Alfred van Geest

Empty cell of Cosmarium anceps (var. anceps) showing an unornamented cell wall.



Desmid of the month
March 2022

Cosmarium anceps

C. anceps is a rather small-sized, smooth-walled Cosmarium species to be recognized by its shallow cell sinus in combination with highly trapeziform semicells. Both apical and lateral sides of the semicell tend to be concave. However, in var. borgei the lateral semicell sides are undulate to a greater or lesser extent. In the Netherlands, Cosmarium anceps is of occasional occurrence on wet substrates and in ephemeral puddles.

Image Hanny Kooijman née Van Blokland © IBED

SEM picture of C. anceps showing that the cell wall is not perfectly smooth but faintly scrobiculate.