Cosmarium quadratum
Image © Alfred van Geest


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



Cosmarium quadratum
Image © Hanny Kooijman née Van Blokland © IBED

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.


Cosmarium quadratum
Image © Hanny Kooijman née Van Blokland © IBED

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.


Cosmarium quadratum
Image © Alfred van Geest

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

Cosmarium quadratum
Image © Alfred van Geest

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


Cosmarium quadratum
Image © André Vanhoof

Zygospore of C. quadratum.