Phylum: Charophyta   Family: Desmidiaceae

Cosmarium perdifficile F.A.C. Kouwets 2025

A recently described species in an effort by Kouwets (2025) to break down the C. difficile complex. It displays the same amount of variability as that species but is smaller, without overlap.
Single cell dimensions: L: 18.8 µm, B: 11.6 µm, Is: 3.1 µm; Th: 8.2 µm, L/B: 1.62.
Found in acidic moorland pools and Sphagnum bogs. Distribution and status unknown in the Outer Hebrides due to possible misidentifications.

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