Image © Henk Schulp
Cell of Euastrum bidentatum var. bidentatum. Note the lateral lobes in between the apical lobes and the basal lobes (the latter, in their turn, are slightly bilobed).
Cell dimensions (L x B): 52 x 35 µm
Eu. bidentatum belongs to the group of Euastra that are characterized by a deep apical incision of the semicell. It somewhat resembles Eu. elegans but differs in the occurrence of lateral semicell lobes in between the basal lobes and the apical lobes. The lateral lobes are placed about half-way the height of the semicell. Whereas, in the Netherlands, the nominate variety of Euastrum bidentatum is rather common in various kinds of slightly acidic, mesotrophic water bodies the variety speciosum, marked by a more pronounced cell wall sculturing, is pretty rare.
Image © Marien van Westen
Cell of Euastrum bidentatum var. speciosum. As compared to var. bidentatum, cell wall sculpturing is much more pronounced resulting in markedly papillate/dentate lobes.
SEM image © Jan Šťastný
SEM picture of Euastrum bidentatum var. speciosum