ELECTRIC CONTROL OF CILIARY BEAT DIRECTION AND CURVATURE OF GLIDING IN LOXODES (CILIATA)

The gliding locomotion of Lokodes on solid surfaces is commonly curved in the counterclockwise direction. Experiments using K+-dependent mod ulation of the membrane potential showed that depolarization induced g liding tracks of clockwise curvature, whereas hyperpolarization induce d an increase of track curvature in the counterclockwise direction. Ga lvanotaxis of Lox-odes in a linear DC-field is unorthodox in that cell s become oriented parallel to the isopotentials with their oral sides facing the cathode. The experimental data were combined with a novel g eometric model which predicts locomotion from differential ciliary act ivity. The model accounts for the body shape, distribution and density of ciliation, and beat direction of the cilia. Ciliary beat direction shifts in the counterclockwise direction (cilia seen tip-to-base) fro m posteriad to anteriad upon membrane depolarization. During hyperpola rization, beat direction is reoriented in the clockwise direction rewa rd the posterior cell end. The characteristics of electromotor couplin g with respect to the beat: direction are in accordance with those whi ch were previously documented in Paramecium.