Triradiate cell of Staurodesmus omearae in frontal view. Notice cup-shaped semicells with apical angles that gradually pass into rather long, divergent spines.
Cell dimensions (L x B, including spines): 27 x 35 µm
Cells of Staurodesmus omearae are relatively small and may be 2-radiate or 3-radiate. Often, within one and the same population, both radiation facies may be present. Not seldom, also Janus forms are encountered: one semicell being 2-radiate, the other one 3-radiate. Cell shape in Std. omearae is not very specific. Semicells are cup-shaped with divergent spines at the apical angles. Zygospores, as in most Staurodesmus species, are globose and provided with rather long spines. Std. omearae is particularly encountered in acidic, oligotrophic habitats. In the Netherlands it is a common inhabitant of bogs and moorland pools. Zygospores are but seldom found.
Image © Alfred van Geest
Biradiate cell of Std. omearae.
Image © Marien van Westen
Dichotypic cell of Std. omearae (so-called Janus form), the upper semicell being triradiate, the lower semicell biradiate.
Image (stacked) © Marien van Westen
Globose, spiny zygospore of Std. omearae.