Desmid of the month
July 2016

Cosmarium tetrachondrum

Cosmarium tetrachondrum, although small-sized and but little remarkable in shape, may be readily identified by its four distinct granules at the base of each semicell. Semicells are depressed semicircular in outline with smooth to weakly undulate lateral margins. The basal granules characteristic of the species are placed on either side of the isthmus. Next to this relatively large isthmial granules often some addtional, but much smaller intramarginal granules may be observed near the basal angles. In Europe, C. tetrachondrum is a rare species with a distinct atlantic distribution. In the Netherlands, at present, it is only known from a single mesotrophic fen area in the province of Friesland.