Cell of Cosmarium pseudopyramidatum. Notice pyramidal shape of semicells, relatively small dimensions and chloroplasts with a single, central pyrenoid.

Cell dimensions (L x B): 51 x 30 µm

Another cell of C. pseudopyramidatum in frontal view containing many starch granules.



Desmid of the month
June 2021

Cosmarium pseudopyramidatum

Cosmarium pseudopyramidatum much resembles Cosmarium pyramidatum . The only difference is in cell dimensions and — linked to that — the number of pyrenoids in the chloroplast. Whereas in C. pyramidatum cell length usually is at least 70 µm and chloroplasts have two or more pyrenoids, cells of C. pseudopyramidatum are less than 60 µm long and their chloroplasts contain but a single pyrenoid. In the Netherlands, C. pseudopyramidatum is widely distributed in acidic, oligotrophic bogs and moorland pools.

Cell of C. pseudopyramidatum in lateral view showing pyrenoids in the centre of radiating chloroplast ribbons.

Empty cell of C. pseudopyramidatum showing cell wall punctation.