Rhabdomonas intermedia Christen, 1962
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Rhabdomonas intermedia
Diagnosis:
- cell cylindrical, not flattened, rigid
- pellicle longitudinal ridged, slighty clockwise
- anterior end slightly obliquely truncated, posterior end rounded
- length 20–24 µm
- canal opening apical
- one flagellum, almost body length
- spherical nucleus below middle
- larger paramylon granules often in anterior half
No drawings from previous authors available.
So far I have only found a few specimens of Rhabdomonas intermedia in an old sample from May 2024 from the Simmelried. It was a sample from the top layer of the bottom mud. After about two weeks, a brown-green fringe rich in small flagellates and euglenids formed on the vessel wall just below the water surface.
I was able to recognize Rhabdomonas intermedia mainly by its cylindrical and compact body with distinct longitudinal furrows. This distinguishes the species from Rhabdomonas costata, whose body is always slightly curved and more slender. The longitudinal furrows of Rhabdomonas intermedia run almost straight to the posterior end. I could only detect a very slight clockwise rotation. In addition, the furrows seem to widen slightly towards the posterior end (s. figs. 1 c and 2 d). The nucleus was always below the middle of the body (s. fig. 1 a) and most of the paramylon grains were found in the front half of the body (s. figs. 1 a and 1 b). The specimens in my population had a fairly constant length of 20–22 µm.
Fig. 1 a-d: Rhabdomonas intermedia. L = 21 µm. Different focal planes of a freely swimming specimen. F = flagellum, Nu = nucleus, PG = paramylon grains. Obj. 100 X.
Fig. 2 a-d: Rhabdomonas intermedia. L = 20 µm. Different focal planes of second a freely swimming specimen. CV ? = probably the contractile vacuole. Obj. 100 X.