Cosmarium difficile
Image © Alfred van Geest

Cosmarium difficile. Notice rather small cell dimensions and hexagonal outline of the semicells.

Cell dimensons (L x B): 24 x 16 µm

 

 

Desmid of the month
May 2019

Cosmarium difficile

C. difficile is a rather small-sized, smooth-walled Cosmarium species with (in frontal view) more or less hexagonal semicells. Its most important diagnostic feature is in the distribution of cell wall pores, viz in three transversal rows: one at the apex, one in the middle part and one at the base of each semicell.
High magnification of empty cells reveals a scrobiculate character of the cell wall.
Zygospores are globose and furnished with broadly rounded, conical protuberances. In the Netherlands, C. difficile is a rather common species in slightly acidic, mesotropic habitats. Zygospores are only known from a single site.


Imege © Alfred van Geest

Another cell of C. difficile showing a central pyrenoid in each semicell.


Image © Alfred van Geest

Empty cell of C. difficile showing transversal series of cell wall pores.

Image Hanny Kooijman née Van Blokland © IBED

SEM picture of C. difficile showing a scrobiculate cell wall and in each semicell an apical, a median and a basal series of cell wall pores.

Image Hanny Kooijman née Van Blokland © IBED
Another SEM picture of a C. difficile cell showing that the cell wall pores in the median series are much closer to each other than in the apical and the basal series.

 


Image © Matthijs Koek

Zygospore of C. difficile. Notice stout, broadly rounded, conical protuberances.