Phylum: Charophyta   Family: Closteriaceae

Closterium venus  J. Ralfs 1848

A small cell with a variable amount of arc. It also supports a tiny end-pore but not always visible. In needs to be compared with the similar Cl. parvulum C. Nägeli 1849, but that species tends to be slenderer and have more pyrenoids per chloroplast. However, parameters do overlap.
Single cell dimensions: L: 77 µm; B: 10.7 µm; Ap: 1.6 µm; Arc: 165°; L/B: 7.
It has been found in acidic and slightly alkaline waters but is proving to be rare in the Outer Hebrides

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Van Westen, M.C. (2024). Sieralgen in Drenthe.