Cell of Cosmarium quadratum in frontal view. Notice oblong outline, rather shallow sinus and semicells with concave lateral sides.
Cell dimensions (L x B): 60 x 35 µm

SEM picture of C. quadratum showing a finely punctate cell wall with a transversal series of minute ‘granules’ (actually, plugs of mucous) at the isthmus.

SEM picture of C. quadratum showing cell wall sculpture at the isthmus in more detail.


Desmid of the Month
July 2024

Cosmarium quadratum

C. quadratum is a medium-sized, largely smooth-walled Cosmarium species. Cells are about oblong in outline with a rather shallow sinus. Usually, lateral sides of the semicells are a bit concave rendering the cell a characteristic appearance. Zygospores are globose and smooth-walled as well. In the Netherlands, C. quadratum is of occasional occurrence in various mesotrophic water bodies. Zygospores are only known from 'Buitengoor' at Mol.

Same cell of C. quadratum in lateral view showing an elliptical outline of its semicells.

Another cell of C. quadratum (in frontal view) showing two pyrenoids in each semicell.

Zygospore of C. quadratum.