Cosmarium neodepressum
Ramos & Moura, 2020
Most likely ID: n.a.
Synonym: Cosmarium depressum
Sampling location: Simmelried
Phylogenetic tree: Cosmarium neodepressum
Diagnosis:
- semi-cells elliptic, slightly depressed
- length 36–56 µm, width 36–60 µm
- sinus narrow, linear
- isthmus narrow
- cell wall covered with fine pores
- one pyrenoid per semi-cell
So far I have only found Cosmarium neodepressum in the Simmelried, where this desmid alga can be found regularly, but never frequently.
Cosmarium neodepressum has unfolded, flat chloroplasts, which makes the specimens appear very transparent and bright. The semi-cells are broadly elliptical with a typical shape. The cell wall is granulated. These are pores through which the often visible gelatinuous sheath is excreted. Bacteria often colonize the surface of this sheath.
Fig. 1 a-b: Cosmarium neodepressum. L = 40 µm. Two focal planes of a young specimen. Note the granulated surface of the cell wall (b). Obj. 100 X.
Fig. 2: Cosmarium neodepressum. L = 38 µm. A specimen in brightfield illumination. Obj. 100 X.
Fig. 3: Cosmarium neodepressum. L = 44 µm. A specimen with a clearly visible gelatinuous sheath (GS). Obj. 40 X.
Fig. 4: Cosmarium neodepressum. A specimen in cell division. Nu = nucleus. Obj. 100 X.