Image © Henk Schulp
Cell dimensions (L x B): ca 110 x 20 µm
The genus Tortitaenia was rather recently split off from the genus Spirotaenia by Brook (1997, 1998) because of a different chloroplast configuration. Whereas in Spirotaenia the chloroplast is a parietal helical tape, in Tortitaenia the chloroplast consists of an axial core provided with a number of spiralling ridges. Pyrenoids (usually a few, big ones) are situated in the central core and only to be seen in optical section of the cell.
Tortitaenia obscura (synonym: Spirotaenia obscura) is the most common representative of the genus. In the Netherlands it is not rare in slightly acidic, mesotrophic habitats.
Brook, A.J., 1997. The proposed establishment of a new desmid genus Polytaenia, previously the sub-genus Polytaenia of the genus Spirotaenia, and a description of a new species, P. luetkemuelleri. — Quekett Journal of Microscopy 38: 7-14.
Brook, A.J., 1998. Tortitaenia nom.nov. pro Polytaenia Brook, a name of a genus of saccoderm desmids — Quekett Journal of Microscopy 38: 146.