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Staurastrum uhtuense Desmid Species Outer Hebrides

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Phylum: Charophyta   Family: Desmidiaceae

Staurastrum uhtuense Grönblad 1921

Cells about as long as broad to marginally longer than broad. Sinus V- or wedge-shaped and always open, cell body is rectangular with long processes set at about 45 degrees. They have about eleven evenly-spaced denticulations circulating the processes, tipped with two medium-sized spines. The semicell near the isthmus has a broad protuberance supporting three denticulations, the centre one being largest. There are paired denticulations at the basal angles. The Loch na Creige population was found at the stoney, shallow, exit-end of an otherwise deep loch, with a slightly alkaline reading of pH 7.2.
A very rare desmid first described by Grönblad (1921, p. 60, pl. 5: 30) from a single specimen found in Northern Russia. In 1938 he found another example in South-West Finland, which was slightly smaller. A tropical species found in Ceylon (now Sri Lanka): Staurastrum columbetoides West & West (1902, p. 186, pl. 22: 8-9) has been likened to St. uhtuense, but it is not a view shared here. They are morphologically quite different. From a German tropical expedition Krieger (1932, p. 195, pl. 15: 21) described Staurastrum columbetoides var. intermedium being intermediate between St. columbetoides and St. uhtuense. His rather sketchy drawing does seem to show features of both species. (Drawings of these four taxa can be seen below.)

Grönblad, R. (1921). New desmids from Finland and Northern Russia with critical remarks on some known species.
Grönblad, R. (1938). Neue und seltene Desmidiaceen.
Krieger, W. (1932). Die Desmidiaceen der Deutschen limnologischen Sunda-Expedition.
West, W. & West, G.S. (1902). A contribution to the freshwater algae of Ceylon.