Phylum: Charophyta   Family: Desmidiaceae

Cosmarium crenatoides P.F.M. Coesel & A. van Geest 2022

One of several confusing species but recent progress has been made in sorting them out. A noted feature of this taxon is the broad inflation above the isthmus with about eight longitudinal parallel series of 3-4 granules. These are best seen in empty cells. Consult the references for more details.
Cell dimensions: L: 34-35 µm, B: 21.3-23.9 µm, Is: 14.4-15.6 µm, Th: 18.4-19.1 µm. L/B: 1.47-1.64.
A rare taxon which probably has an Arctic-alpine distribution. Found in ephemeral pools and shallow depressions.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.
Van Westen, M.C. (2024). Sieralgen in Drenthe.