Plagiocampa rouxi Kahl, 1926
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried, Mindelsee
Phylogenetic tree: Plagiocampa rouxi
Diagnosis:
- body obovate to ellipsoid
- length 35–50 µm
- oral apparatus apical with 8 finger-shaped flaps
- spherical macronucleus (8 µm) central with several nucleoli
- spherical micronucleus (2 µm) adjacent to macronucleus
- cytoplasm filled with granula (often ring-shaped)
- contractile vacuole almost terminal
- one caudal cilium, about 18 µm long
I find Plagiocampa rouxi only very rarely and so far only in the Simmelried and in the reedbeds of the Mindelsee. The specimens have always been found in samples with decomposing plant material.
At low magnification Plagiocampa rouxi can easily be confused with oval ciliates of comparable size such as Urotricha ovata. The special structure of the mouth opening only becomes apparent at high magnification. This lies apically, is slit-shaped and surrounded by 8 finger-shaped flaps in a semicircle (s. figs. 1 c and 1 d). These flaps continuously fan out towards the mouth opening.
The specimens in my population were quite small at around 35 µm, but show all the characteristics of Plagiocampa rouxi. The ring-shaped granula, which was mainly located in the anterior half of my specimens, was neither mentioned by Kahl (1926) nor by Foissner, Berger and Kohmann (1994). Only Omar & Jung (2023) describe the ring-shaped granules in a description of a population of Plagiocampa rouxi from South Korea. Kahl mentions ring-shaped granula only for the related species Plagiocampa metabolica. However, this species is said to have no caudalcilium.
Fig. 1 a-d: Plagiocampa rouxi. L = 35 µm. Different focal planes of a freely swimming specimen. Note the finger-shaped flaps (FF) surrounding the slit-shaped mouth. CC = caudal cilium, CV = contractile vacuole, Ma = macronucleus, Mi? = probably the micronucleus, RG = ring-shaped granules. Obj. 100 X.
Fig. 2 a-b: Plagiocampa rouxi. L = 36 µm. A second specimen. CC = caudal cilium. Obj. 100 X.
Fig. 3: Plagiocampa rouxi. A strongly squashed specimen L = 35 µm. Different focal planes of a freely swimming specimen. In the macronucleus (Ma) parietal nucleoli (Nuc) are visible. Obj. 100 X.