Cell of Cosmarium dickii. Notice subsemicircular, crenate outline of semicells.
Cell dimensions (L x B): ca 24 x 20 µm

Empty cell of C. dickii. Notice couple of granules close to the isthmus.


Desmid of the month
February 2024

Cosmarium dickii

Cosmarium dickii is a rather small-sized, granulate Cosmarium species. Semicells are subsemicircular in outline with some 14 marginal crenations in line with some intramarginal, concentric series of granules. In the semicell centre usually a tubercular inflation may be distinguished. Most characteristic feature, however, is the presence of two marked granules just above the isthmus. Zygospores are globose and furnished with short, mamillate protuberances. In the Netherlands, C. dickii is of occasional occurrence in various mesotrophic water bodies. Zygospores are only known from a single site in Belgian Flanders.

SEM picture of C. dickii showing ornamentation in detail. Image © Marien van Westen.

Zygospore of C. dickii. Notice mamillate protuberances.