Crucigenia fenestrata
(Schmidle) Schmidle, 1900
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Pond of the convent Hegne
Phylogenetic tree: Crucigenia fenestrata
Diagnosis:
- coenobia of 4 cells, rhomboidal or rectangular
- forming composite syncoenobia without gelatinous sheath
- cells trapezoid, 5–12 X 2–6 µm
- chloroplast small, fills cell only partly
- pyrenoid absent
- planktonic lifestyle
So far, I have only found Crucigenia fenestrata in the pond of the convent Hegne, where this small green alga is very rare.
The cenobia in my population were all approximately square and always consisted of four cells. I have not yet found any larger associations of several coenobia forming syncoenobia.
The trapezoidal cells have only one chloroplast without a pyrenoid, which is always attached to the outer cell wall. In the center, the chloroplast has a small notch where the cell nucleus is located.
Fig. 1: Crucigenia fenestrata. D = L = 12.6–12.8 µm (of coenobia). Three rectangular coenobia embedded in an agglomerate of bacteria. The cells have a length of 7.7–8.7 µm. Obj. 100 X.
Fig. 2 a-b: Crucigenia fenestrata. D = 13.6 µm (of coenobium). Two focal planes of a single coenobium. Note the small nucleus (Nu) located in a notch of the chloroplast. Obj. 100 X.