Vorticella natans (Fauré-Fremiet, 1924)
Most likely ID: n.a.
Synonym: Vorticella convallaria var. natans
Sampling location: Hagstaffel pond
Phylogenetic tree: Vorticella natans
Diagnosis:
- length 70 – 100 µm, width 50 µm
- cells bell-shaped, posterior end curved in swimming direction
- contracted cells oviform
- plasm colorless
- one contracile vacuole
- macronucleus J-shaped
- pellicle finely striated
- stalk contracts in spirals
- solitary, planktonic, swims with the stalk in front
I found the planktonic Vorticella natans in the Hagstaffler pond in 1998. The stalk is not attached to a solid substrate, but tapers at the distal end. When swimming, the stalk is elongated and points in the swimming direction. The cell body is also bent in the swimming direction and provides propulsion with the cilia of the peristome. Upon contact with an obstacle, the anterior part of the stalk contracts in spirals, while the distal end does not spiral. Moreover, the stalk cannot perform any other movements, which is a simple feature safely distinguishing Vorticella natans from Vorticella mayeri, the second planktonic Vorticella species. In Vorticella mayeri, the stalk can whip to achieve faster propulsion.
Vorticella natans was transferred to Pelagovorticella by Jankowski in 1985, but this was not accepted.
Fig. 1: Vorticella natans. L = 77 µm (without stalk). A freely swimming specimen. Obj. 10 X.
Fig. 2 a – b: Vorticella natans. L = 77 µm (without stalk). An extended, freely swimming specimen (a) and a the same specimen contracted (b). Note that only the first half of the stalk is spiralized (arrow). The distal half of the stalk will not spiralized. Obj. 20 X.