Phylum: Charophyta   Family: Closteriaceae

Closterium setaceum J. Ralfs 1848

First described by Brébisson in Ralfs (1848: 176, pl. 30: 4) and illustrated by Jenner.
Cell dimensions: L: 220-450 µm; B: 8-13 µm; Ap: 1.8-2.1 µm; L/B: (10-)25-37.
Zygospore: c.30 x 32 µm.
West & West (1904: p. 190, pl. 26: 9-13) describe it as widespread but much rarer than C. kuetzingii. It is slenderer and has fewer pyrenoids (usually 3 per chloroplast). Found in nutrient-poor lochs in the marginal vegetation.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Ralfs, J. (1848). The British Desmidieae.
Van Westen, M. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1904). A Monograph of the British Desmidiaceae, Volume 1.