Cosmarium regnesi Reinsch, 1866
Most likely ID: n.a.
Synonym: Cosmarium regnesii
Sampling location: Simmelried
Phylogenetic tree: Cosmarium regnesi
Diagnosis:
- cell as wide as long
- semi-cells almost rectangular
- apices slightly concave
- each 6 warts per semi-cell
- warts often colored brown-orange (iron inclusions)
- length 6–11 µm
- sinus widely open, U-shaped
- one chloroplast with one pyrenoid per semi-cell
So far I have only found Cosmarium regnesi once in 2005 in the Simmelried. After that I have no more evidence.
Cosmarium regnesi is one of the smallest members of the genus and is easy to overlook in fresh samples. The main characteristics are the U-shaped, wide-open sinus and the few but conspicuous warts on the half-cells. In my population, these warts were colored brown-orange due to iron inclusions. The cell is about as long as it is wide and therefore somewhat square in outline.
The species Cosmarium regnesi shows a certain variability but the square cell outline and the U-shaped sinus are always preserved.
Fig. 1 a-b: Cosmarium regnesi. L = 8.4 µm. Two focal planes of a specimen found 2005 in the Simmelried. Obj. 100 X.