Desmid of the month
September 2011
Cosmarium nymannianum
Like Cosmarium venustum (desmid of March 2010) C. nymannianum is a distinctly oligotrophic bog species, morphologically marked by a coarsely scrobiculate cell wall (with an extra large pit in the centre of the semicell). As compared to C. venustum, cells of C. nymannianum are larger sized and less undulate at the lateral sides (2-undulate versus 3-undulate). In the Netherlands, C. nymannianum is a rather rare species.
mouse over image Hanny Kooijman – van Blokland, © IBED
SEM picture of C. nymannianum. Notice large central pit in the cell wall surrounded by scattered scrobicles and cell wall pores (not per se connected with scrobicles).
Mouse over: Close-up of central cell wall pit linked up with a central pore.
Cosmarium nymannianum. Semicells are trapeziform in outline with concave lateral sides and apex.
Cell dimensions (L x B): ca 50 x 40 µm
Image © Marien van Westen
Another cell of C. nymannianum showing a large central pyrenoid in each semicell.
