Phylum: Charophyta   Family: Closteriaceae

Closterium idiosporum var. punctatum (H. Skuja) W. Krieger 1935

First described and illustrated by Skuja (1928: 135; pl. 2: 13-16) as Closterium punctatum. It was later made a variety by Krieger (1935: 272). This and the nominate variety can only be reliably separated when found with the zygospores; rectangular in var. punctatum, elliptical in the nominate.
Cell dimensions: L: 170-248 µm; B: 4.8-7.7 µm; Ap: 1.5-2.4 µm; L/B: 28-34.
Zygospore dimensions: 44-45 x 21-22 µm.
Common in acidic moorland pools and loch-margins, also with Sphagnum.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Krieger, W. (1935). Die Desmidiaceen Europas mit Berücksichtigung der aussereuropäischen Arten.
Skuja, H. (1928). Vorarbeiten zur einer Algenflora von Lettland. IV.
Van Westen, M. (2024). Sieralgen in Drenthe.