Phylum: Charophyta   Family: Desmidiaceae

Cosmarium reniforme (J. Ralfs) W. Archer 1874

It has become clear in recent years that Cosmarium reniforme is a complex. This nominate variety is common in the Outer Hebrides but still need to be carefully compared with similar taxa. The first image depicted below displays characteristics of C. reniforme and the recently described C. pseudoreniforme M.C. van Westen 2015.
Cell dimensions: L: 43-59 µm; B: 42-54 µm; Is: 14.7-20 µm; Th: 23-26 µm; L/B: 1.0-1.12.
Found in slightly acidic habitats such as vegetated loch-margins, moorland pools and abandoned peat-cuttings.

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