Phylum: Charophyta   Family: Desmidiaceae

Staurastrum pentasterias Grönblad 1963

Grönblad (1963, p. 30, pl. 5: 35) gives very precise measurements suggesting just one cell was found: L: 30, B: 36.8, Is: 9.2 µm (the isthmus is particularly narrow). Lenzenweger (1997, p. 113, pl. 33: 15) gives: L: 30-33, B: 32-38, Is: 12-13 µm. The population from North Uist is slightly larger at: L: 34.8-35.5, B: 38.6-41.3, Is: 14.5-15.7 µm. There is possible confusion with other 5-radiate taxa but well observed populations are well defined. Found in oligo-mesotrophic waters including with Sphagnum, but would seem rarely recorded.

References: 
Grönblad, R. (1963) Desmids from Jämtland, Sweden and adjacent Norway.
Lenzenweger, R. (1997) Desmidiaceenflora von Österreich, Teil 2.
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus.