Cosmarium tumidum Lundell, 1871
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Schwemm Moor (Austria)
Phylogenetic tree: Cosmarium tumidum
Diagnosis:
- semi-cells broadly ellipsoidal
- length 30–40 µm, width 25–30 µm
- cell wall scattered pores
- central areas of semi-cells with flat protuberances
- one chloroplast with one pyrenoid per semi-cell
So far, I have only found Cosmarium tumidum in the Schwemm Moor in Austria. Only a few specimens were found in the samples.
Cosmarium tumidum is a rather inconspicuous and small species. Its main characteristics are its cell wall with scattered small pores and a central protuberance on the sides of the semi-cells. These protuberances can only be seen when focusing carefully (s. fig. 1 b).
Cosmarium tumidum can easily be confused with Cosmarium subtumidum. However, this species has slightly trapezoidal semi-cells, while the semi-cells of Cosmarium tumidum are clearly broad elliptical.
Fig. 1 a-b: Cosmarium tumidum. L = 32. Two focal planes of a specimen in DIC. The cell wall is covered with small pores and in the central areas of each semi-cell the protuberances (CP) are visible. Obj. 100 X.
Fig. 2 a-b: Cosmarium tumidum. L = 32. The same specimen as shown in fig. 1 a-b in brightfield illumination. Obj. 100 X.