Brachonella pulchra
(Kahl, 1927) Bourland et al., 2018
Most likely ID: n.a.
Synonym: Metopus pulcher
Sampling location: Simmelried
Phylogenetic tree: Brachonella pulchra
Diagnosis:
- body broadly ellipsoidal or obovoidal
- length 80–110 µm
- adoral zone running almost a full turn around longitudinal axis
- on ventral side adoral zone runs diagonally bevor it bends to continue in parallel to longitudinal axis
- mouth opening in posterior fourth of body
- macronucleus globular
- fringe of inconspicuous extrusomes beneath pellicle
- contractile vacuole terminal
- posterior end broadly rounded
- slightly elongated caudal cilia
I have found Brachonella pulchra so far exclusively in the uppermost mud layer in Simmelried. The species is not very common. In the last 20 years I could observe only a few specimens. I recognize Brachonella pulchra by the very posteriorly located mouth opening (s. fig. 1 b) and the course of the adoral zone, which runs almost around the entire body and suddenly turns posteriorly on the ventral side, almost in parallel to the longitudinal axis. At the broadly rounded posterior end a few, slightly elongated caudal cilia arise, which can be easily overlooked. As already described by Kahl, the species is quite variable. So I could observe a smaller form in December 1998, which was only 84 µm long (s. fig. 2 a-d).
Fig. 1 a-f: Brachonella pulchra. L = 108 µm. A freely swimming specimen from ventral (a, b), from right (c, d) and from dorsal (e, f). AZM = adoral zone of membranelles, CC = caudal cilia, CV = contractile vacuole, Ma = macronucleus, MO = mouth opening, PC = perizonal cilia. Obj. 60 X
Fig. 2 a-d: Brachonella pulchra. L = 84 µm. A second, freely swimming specimen from ventral. Obj. 40 X