Acineta tuberosa
(Pallas, 1766) Ehrenberg, 1833
Most likely ID: n.a.
Synonyms: Brachionus tuberosas, Acineta fluviatilis
Sampling location: Mühlhalden pond
Phylogenetic tree: Acineta tuberosa
Diagnosis:
- lorica 25-200 µm long, 25-80 µm wide
- cell slender or broadly triangular, compressed, fills the lorica
- stalk 2-4 µm in diameter, few µm to 800 µm long
- two spherical protruding ends with 3 – 30 tentacles each (usually 10 – 20)
- tentacles up to 80 µm long
- macronucleus globose or ellipsoidal in mid-body
- some attached micronuclei
- one contractile vacuole in anterior half
- swarmer ellipsoidal, 30 – 35 µm long, with oblique rows of cilia
I find the suctor Acineta tuberosa exclusively in the Mühlhalden pond near the village Dettingen. This pond has an overflow in a concrete basin, where the water flows off with high velocity. In this fast flowing water long tufts of algae (e.g. Oedogonium) grow, which are densely colonized by Acineta tuberosa in huge quantities (s. fig. 1). The algal filaments from this location are colonized exclusively by this suctor. I have not found any other species on it. Acineta tuberosa can be recognized quite easily by the triangular or Y shape with the two bundles of tentacles. There is only one contractile vacuole and the cell completely fills the lorica. A completely reliable identification is possible by the swarmer (s. fig. 7 a-d). Due to the amount of individuals available I have found very many swarmers. The swarmers of Acineta tuberosa have no reduced tentacles (like the swarmers of many other species) but oblique rows of cilia.
Fig. 1: Acineta tuberosa. A mass development on algae filaments. Obj. 20 X.
Fig. 2: Acineta tuberosa. A group of individuals on an alga filment. Obj. 40 X.
Fig. 3: Acineta tuberosa. A group of specimens on an algae filament. Obj. 60 X.
Fig. 4 a-c: Acineta tuberosa. L = 82 µm (without stalk). Three focal planes of an unsquashed specimen with extended tentacles (TE). CV = contractile vacuole, Ma = macronucleus, Mi = micronuclei, ST = stalk. Obj. 60 X.
Fig. 5: Acineta tuberosa. L = 55 µm (without stalk). A second unsquashed specimen in detail. Obj. 100 X.
Fig. 6: Acineta tuberosa. Apical view of the extended tentacles of a specimen. Obj. 100 X.
Fig. 7 a-d: Acineta tuberosa. Four focal planes of a freely swimming swarmer. The swarmer is 31 µm long. Note the obliquely running ciliary rows (a, b). arrow = swimming direction, CV = contractile vacuole, Ma = macronucleus. Obj. 100 X.