Micrasterias ralfsii
(Brébisson ex Ralfs) Škaloud, Nemjova, Vesela, Černá & Neustupa, 2011
Most likely ID: n.a.
Synonym: Cosmarium ralfsii
Sampling location: Lauchsee Moor (Austria)
Phylogenetic tree: Micrasterias ralfsii
Diagnosis:
- cells almost circular, slightly longer than wide
- length 90–120 µm, width 80–110 µm
- semi-cells almost semi-circular, rounded basal angles
- apices flat, slightly convex
- cell wall finely punctate with scattered pores
- sinus deep, linear, laterally strongly widened
- chloroplasts with several, scattered pyenoids
The original name Cosmarium ralfsii was set invalid by Škaloud et al. in 2011 on the basis of genetic studies and the species was transferred to the genus Micrasterias.
I have only found Micrasterias ralfsii in the Lauchsee Moor in June 2024. The alga was quite common there. It is similar in shape to Cosmarium circulare, but has flattened apices and has several, scattered pyrenoids, while Cosmarium circulare has only 2 pyrenoids per semi-cell.
Fig. 1 a-b: Micrasterias ralfsii. L = 116 µm. Focal planes on the isthmus (a) and the finely punctate cells wall (b). Obj. 100 X.
Fig. 2: Micrasterias ralfsii. L = 116 µm. The specimen as shown in fig. 1 a-b at higher magnification. Obj. 100 X.
Fig. 3 a-b: Micrasterias ralfsii. L = 116 µm. The specimen as shown in fig. 1 a-b in brightfield illumination. Obj. 100 X.