Euastrum ventricosum Lundell, 1871
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Schwemm Moor (Austria)
Phylogenetic tree: Euastrum ventricosum
Diagnosis:
- semi-cells slightly 5-lobed, almost trapezoidal
- length 100–120 µm, width 55–65 µm
- deeply constricted with a narrow, linear sinus
- lateral margins concave
- apical lobe separated by deep incision
- three basal protuberances near isthmus
- two central protuberances
- one central pore in each semi-cell
- cell wall punctate
- chromatophores with several, scattered pyrenoids
So far, I have only found Euastrum ventricosum in the Schwemm Moor (Austria). There, the species occurs in large numbers in some places.
The semi-cells of Euastrum ventricosum are slightly trapezoidal with 5 faint lobes. The apical lobes have a deep incision that is closed at the top. The lateral margins of the semi-cells are concave. This distinguishes Euastrum ventricosum from the similar species Euastrum crassum. In addition, the semi-cells of Euastrum ventricosum have three basal protuberances and two in the middle of the semi-cells (s. fig. 2 c). Euastrum crassum lacks these two middle protuberances. However, both species have a central pore in the middle of each semi-cell (s. fig. 2 d).
Fig. 1 a-b: Euastrum ventricosum. L = 118 µm. Two focal planes of a specimen in brightfield illumination. Obj. 100 X.
Fig. 2 a-d: Euastrum ventricosum. L = 118 µm. Different focal planes of the same specimen as shown in fig. 1 a-b in DIC. Note the 5 protuberances (*) and the central pores (CP) of the semi-cells. Obj. 100 X.