Micrasterias pinnatifida Ralfs, 1848
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Determoor (Austria)
Phylogenetic tree: Lepadella biloba
Diagnosis:
- outline broadly oval
- length 40–80 µm, width 37-90 µm
- apices flat or slightly convex
- semicells 3-lobed, with the 2 interlobular incisions
- lobes projecting horizontally
- walls minutely punctate
So far I have only found Micrasterias pinnatifida once in 1996 in the Determoor (Austria) in a few specimens. After that I have not found any more specimens, although this alga is described as adaptable and widespread.
Micrasteris pinnatifida stands out due to its small size and comparatively simple structure of the lobes. Each half-cell is three-lobed. The lobes each have a pair of short spines at their ends. The chloroplasts are described to contain “several” pyrenoids (Förster, 1982). In my population there were mostly 2–3 pyrenoids present.
Fig. 1 a-b: Micrasterias pinnatifida. L = 72 µm. A slightly squashed specimen found 1996 in DIC (a) and in darkfield illumination (b). Obj. 40 X.