Phylum: Charophyta Family: Desmidiaceae
Staurastrum boreale W. & G.S. West 1905
First described and illustrated by West & West (1905: 27, pl. 2: 25). A widespread species but easily confused with the very similar Staurastrum gracile, both morphologically and in ecological preference. The zygospore is rarely recorded and has 6–7 projections in face-view, with 3-4 apical appendages. S. gracile has 8-9 (-10). (This is based on a record by Homfeld in 1929 - see the entry for S. gracile.)
Cell dimensions: L: 25-35 µm; B: 29-41 µm; Is: 9.0-10.5 µm.
Zygospore: minus projections: 22-30 µm; overall: 38-50 µm.
A common species found in slightly acidic, mesotrophic, waters such as shallow vegetated pools and loch-margins.
References:
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
West, W. & West, G.S. (1905). Freshwater algae from the Orkneys and Shetlands.