Cell of Cosmarium portianum. Notice reniform semicells and elongate isthmus.
Cell dimensions (L x B): 38 x 31 µm

Cell of C. portianum in lateral view.



Desmid of the month
April 2014

Cosmarium portianum

C. portianum is a medium-sized granulate Cosmarium that may be readily identified by its reniform semicells and a distinctly elongate isthmus. Cell wall granules are arranged in regular transverse and longitudinal series. The globose zygospore is furnished with obtuse-conical protuberances. In the Netherlands, C. portianum is of occasional occurrence in mesotrophic fen hollows and moorland pools. Zygospores have only been encountered a few times.

Another cell of C. portianum showing regular arrangement of cell wall granules.

SEM picture of C. portianum. Notice regular longitudinal and transverse series of cell wall granules.

Cell of C. portianum in apical view displaying a broadly elliptic semicell outline.

Zygospore of C. portianum. Notice stout, obtuse-conical protuberances.