Nagel U, Machemer H, Bräucker R (1997) Electric control of ciliary beat direction and curvature of gliding inLoxodes (Ciliata). 


The gliding locomotion of Loxodes on solid surfaces is commonly curved in the counterclockwise direction. Experiments using K+-dependent modulation of the membrane potential showed that depolarization induced gliding tracks of clockwise curvature, whereas hyperpolarization induced an increase of track curvature in the counterclockwise direction. Galvanotaxis of Loxodes in a linear DC-field is unorthodox in that cells become oriented parallel to the isopotentials with their oral sides facing the cathode. The experimental data are in agreement with a novel geometric model which predicts locomotion from voltage-dependent ciliary activity. The model accounts for the body shape, distribution and density of ciliation, and beat direction of the cilia. According to the model, ciliary beat direction shifts in the counterclockwise direction (cilia seen tip-to-base) from posteriad to anteriad upon membrane depolarization. During hyperpolarization, beat direction is reoriented in the clockwise direction toward the posterior cell end. The characteristics of electromotor coupling with respect to the beat direction are in accordance with those which were previously documented in Paramecium.