Phylum: Charophyta   Family: Closteriaceae

Closterium acutum var. variabile  (E. Lemmermann) W. Krieger 1935

First described and illustrated by Lemmermann (1896: 118, figs 12-14) as Closterium pseudospirotaenium var. variabile. It was later renamed by Krieger (1935: 262, pl. 13: 18-22). It differs in being either helical or strongly curved.
Cell dimensions: L: 100-150 µm; B: 2.5-5 µm; Ap: 1.3-2 µm; L/B: 15-40.
A strange but relatively common taxon found in moorland pool and vegetated loch-margins.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Krieger, W. (1935). Die Desmidiaceen Europas mit Berücksichtigung der aussereuropäischen Arten.
Lemmermann E. (1896). Zur Algenflora des Riesengebirges.