Image ©Henk Schulp
Tetmemorus brebissonii. Note the cylindric cell shape and the apical invagination which are characteristic of the genus Tetmemorus.
Cell dimensions (L x B): ca 130 x 25 µm.
Just like in Euastrum oblongum (our desmid of the last month) cells of the genus Tetmemorus are marked by a deep, closed apical invagination. In contrast to the genus Euastrum, however, Tetmemorus cells are not flattened but cylindric or fusiform (so in transversal section almost circular, not elliptic-rhomboid as in Euastrum). World-wide, the genus Tetmemorus numbers only a few species. T. brebissonii differs from the other species in that the cell wall pores are arranged in longitudinal series. In the Netherlands, T. brebissonii in its occurrence is strictly confined to acidic, oligotrophic bog pools.
Image © Henk Schulp
Empty cell of Tetmemorus brebissonii showing the longitudinal series of cell wall pores characteristic of this species.