Electrical Recording from the Contractile Ciliate Zoothamnium Geniculatum Ayrton

The spherical body (200 μm in diameter) of this ciliate protozoan was easily immobilized on a suction pipette and penetrated with glass microelectrodes. No recordings could be made from the contractile stalk, but in the body a negative potential of 30· 3 ± 12· 5 mV was observed. Approximately 9 ms after the onset of a mechanical stimulus, a rapid depolarization was observed. This was apparently simultaneous throughout the body surface. The amplitude was 38· 9 ±13· 7 mV. Recordings with a photomultiplier showed that contraction of the stalk began 10 ms later. A slower depolarization of complex form was observed during systole of the contractile vacuole.