Phylum: Charophyta   Family: Desmidiaceae

Cosmarium isthmochondrum C.F.O. Nordstedt 1873

Significant features include a smooth outline, faintly undulate, two prominent subapical granules, a papilla on the basal angles, a large supraisthmial granule and two pyrenoids per semicell.
Single cell dimensions: L: 34.8 µm; B: 31.3 µm; Is: 10 µm; L/B: -1.12.
A rare cell with an Arctic-alpine distribution. Found in mesotrophic, slightly acidic, moorland pools and shallow vegetated lochs.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.