Closterium closterioides var. intermedium
(J.Roy & Bisset) Ruzicka, 1973
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Schwemm Moor (Austria)
Phylogenetic tree: Closterium closterioides var. intermedium
Diagnosis:
- cells broadly spindle-shaped. apices broadly rounded
- length 90–140 µm, width 19–30 µm
- two chloroplasts, sometimes with a constriction or bibartite
- chloroplasts with 4 longitudinal ridges
- 2–5 pyrenoids per chloroplast
- pyrenoids spherically or elongated
- cell wall smooth and colorless
- girdle bands absent
- terminal vacuoles filled with 2–3 crystals
So far I have only found Closterium closterioides var. intermedium in the Schwemm Moor in Austria. However, only isolated specimens were found in the samples.
Compared to the parent form Closterium closterioides, the variety Closterium closterioides var. intermedium is only half the size. The stem form can grow up to 450 µm long. The chloroplast of Closterium closterioides var. intermedium often has a constriction in the middle or can even be in two parts (s. fig. 1 a). In such specimens there are then 4 chloroplasts. The pyrenoids can be either round or elongated ellipsoid. In my population, the specimens of Closterium closterioides var. intermedium each had two round pyrenoids per chloroplast (s. fig. 1 a).
The similar species Closterium navicula has a more stocky shape and is only half the size of Closterium closterioides var. intermedium, usually around 50 µm. Closterium navicula usually has only one pyrenoid per chloroplast and only rarely two.
Fig. 1 a-c: Closterium closterioides var. intermedium. L = 106 µm. Three focal planes of a specimen with a slight constrictions of the chloroplasts (arrows). The cell wall is smooth and colorless (c). Obj. 100 X.