Cosmarium pyramidatum
Brébisson ex Ralfs, 1848
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Lauchsee Moor (Austria), Sima Moor (Austria), Determoor (Austria)
Phylogenetic tree: Cosmarium pyramidatum
Diagnosis:
- cells elongate elliptical
- length 51–115 µm, width 39–70 µm
- semi-cell trapezoidal with flat convex apex
- lateral margin convex
- 1–6 pyrenoids per semi-cell, commonly 2–3 pyrenoids
- sinus deep, straight, internally dilated
- cell wall with punctate with distinct pores
So far I have only found Cosmarium pyramidatum in Austrian bogs, where the species is very common. The cells have a quite characteristic shape, as the semi-cells are pyramidal with a flat apex. The number of pyrenoids per semi-cell is very variable (1-6). In the populations I observed there were always 3 pyrenoids per semi-cell. The cell wall has no ornamentation and only shows pore openings.
Fig. 1 a-b: Cosmarium pyramidatum. L = 88 µm. Two focal planes on the pyrenoids (PY) and the granulated cell wall. Obj. 100 X.
Fig. 2 a-b: Cosmarium pyramidatum. L = 88 µm. The specimen as shown in fig. 1 a-b in brightfield illumination. Obj. 100 X.
Fig. 3 a-b: Cosmarium pyramidatum. L = 85 µm. Two focal planes of a second specimen. Obj. 100 X.
Fig. 4 a-b: Cosmarium pyramidatum. L = 78 µm. A third specimen found in July 2017 in the Sima Moor. Obj. 100 X.