So far I have only been able to find Synura spinosa in the Simmelried, where the species is very rare. The species usually occurs mainly in spring.

The shape of the cells and colonies of Synura spinosa is very variable. Mostly I find oval colonies with slender, slightly club-shaped cells. Very rarely I find ribbon-shaped colonies with almost triangular cells (s. figs 1 a-b and 3 a-b). The latter variant was named Chlorodesmus hispidus by Philipps (1882). In 1994, however, Calado and Rino were able to show that it is also Synura spinosa, due to the identical scale shape.

For a reliable identification of Synura spinosa it is necessary to evaluate the exact shape of the silica scales covering the body of the cells. In Synura spinosa these are oval with a thickened margin and a straight spine (s. figs. 2 and 4). The spine is about as long as the scale. The scales of Synura spinosa in my population were 6.3-6.7 µm long.

Since I found both oval colonies with club-shaped cells and the ribbon-shaped colonies with triangular cells, which Philipps described as Chlorodesmus hispidus, I was able to compare the scales of both shape variants directly. They are absolutely identical (s. figs. 2 and 4) and I can therefore confirm the synonymization with Synura spinosa by Calado and Rino.

More images and information on Synura spinosa: Michael Plewka-Freshwater life-Synura spinosa