Phylum: Charophyta   Family: Desmidiaceae

Cosmarium leursii F.A.C. Kouwets 2025

A recently described species named after its collector, Wil Leurs. A small cell with a narrow isthmus, basal angles rounded almost to the median point, upper half of sides convergent and concave, apices truncate and slightly retuse. Side and apical views show an obvious protuberance.
Cell dimensions: L. 10-11.2 µm; B. 9.6-10.7 µm; Is. 2.5-2.9 µm; Th. 6.8-7.9 µm; L/B. 1.05-1.11.
The original find was from plankton in a eutrophic lake among a bloom of Desmodesmus species. The Outer Hebrides sample came from an equally unique habitat: an artificial water tank containing aquatic algae and bladderwort (Utricularia vulgaris) with a pH of 7.6.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium. Part 1: Text. Part 2: Plates.