image ‘normal’ cells: @ Frans Roefs
Cell size (L x B): ca. 50 x 50 µm
Staurodesmus convergens (in some traditional floras to be found under the name of Arthrodesmus convergens) is characterized by flattened, ellipsoid semicells, with at each pole a stout spine. The species in question has a worldwide distribution and in the Netherlands it is rather common in its appropriate habitat, i.e., shallow, slightly acid, mesotrophic water bodies. If cells are well developed, S. convergens hardly can be confused with any other species. However, for some reason, formation of spines fails to turn up sometimes. In that case Staurodesmus convergens closely resembles Cosmarium depressum. Being aware of the possibility of confusion, a right identification may be helped along by considering other morphological characteristics, such as cell dimensions (which in S.convergens usually are larger than in C. depressum).
image © Henk Schulp