Comasiella arcuata var. platydisca
(G.M. Smith) Hegewald & Wolf, 2010
Most likely ID: n.a.
Synonyms: Scenedesmus platydiscus , Scenedesmus arcuatus var. platydiscus, Scenedesmus obtusus f. obtusus
Sampling location: Bussenried, Simmelried
Phylogenetic tree: Comasiella arcuata var. platydisca
Diagnosis:
- coenobia of 4–8–16 cells, arranged in 2 rows
cells 7–18 µm long, width 3–9.9 µm - cell surface smooth
- cells ovoid to cylindrical or curved (bean-shaped) with rounded apices
- cells touch each other at their apices and longitudinal sides
- with perforations between the apical contact points of the cells
- one pyrenoid per cell
I have found Comasiella arcuata var. platydisca so far in the Bussenried as well as in the Simmelried. For identification it is important that the cells are staggered in two rows by half a cell width and that there is a small space between the contact points in the midline of the colony (s. fig. 1 a), where the cells are not in contact. In my population, the cells of the coenobia were almost always bean-shaped.
Fig. 1 a-b: Comasiella arcuata var. platydisca. L = 24 µm (of coenobium). Two focal planes of a coenobium of 8 cells. The cells are bean-shaped and 10–12 µm long (width 5 µm). The surface of the cells is smooth (b). Note the pore between the contact points of the apices of the cells (arrowheads). Obj. 100 X.