Cosmarium humile
mouse over mages © Alfred van Geest

Cosmarium humile. Notice semicells consisting of a broad, at the lateral margins somewhat undulate basal part and a smaller, rectangular apical part. Notice also the apical series of granules causing a regularly crenate outline of the apex.

Cell dimensions (L x B): 25 x 22 µm

 

 

Desmid of the month
February 2018

Cosmarium humile

C. humile is one of the many small-sized Cosmaria the cell wall of which is sculptured by both incurvations and granules. C. humile may be recognized in that the lateral sides of the semicells show a deep subapical incurvation dividing the semicell in a broad basal part and a smaller, rectangular apical part. Cell wall is provided with a central tubercle and a number of marginal and intramarginal granules the expression of which may widely vary. In particular the apical series of granules cause a regularly crenate appearance of the semicell outline. In the Netherlands, C. humile is a rather common species in various kinds of circumneutral, meso-eutrophic water bodies.

Image © Marien van Westen

Empty semicell of C. humile in top view showing the apical pattern of granulation.

 

 

Image: Hanny Kooijman née Van Blokland © IBED

SEM picture of Cosmarium humile. Notice (flattened) central tubercle as well as  series of (intra)marginal granules (white dots represent mucilaginous pore excretions).

Image: Hanny Kooijman née Van Blokland © IBED

SEM picture of another cell of C. humile marked by a more expressed cell wall sculpturing.