Desmid of the month
April 2004

Cosmarium holmiense

Cosmarium holmiense belongs to a group of desmid species characterized by a predominantly arctic-alpine distribution. Remarkably enough, part of those species may also be encountered in European lowland regions, particularly in hemi-atmophytic, pH circumneutral habitats. Such environmental conditions are, e. g., met with in shallow dune pools which dry out periodically. In the Dutch Dune District Cosmarium holmiense, in particular var. integrum, is far from rare; especially sampling of wet moss cushions may be lucrative.

Cosmarium holmiense var. integrum may be recognized readily by its broad isthmus and especially by semicells which are abruptly constricted just below the apex.

Cosmarium holmiense
Image ©Henk Schulp

Cosmarium holmiense var. integrum (in between a cell of the diatom Synedra and part of a filament of the green alga Zygnema) as encountered in a Dutch dune pool.

Cell dimensions (L x B): ca 55 x 30 ┬Ám.