KINESIS IN EUPLOTES VANNUS - ETHOLOGICAL AND ELECTROPHYSIOLOGICAL CHARACTERISTICS OF CHEMOSENSORY BEHAVIOR

Equally dispersed Euplotes vannus cells accumulate inside a drop of su pernatant of a bacteria suspension that is surrounded by a reference s olution. In the drop, frequencies of stops and backward jerks are tenf old increased. The sequences of directional changes and translocations prevent cells from leaving the chemostimulant region, as if they were trapped. This behavior is quickly induced after casual arrival in the drop and nor by chemotactic influence over a larger distance. With in tracellular recordings, we have found a K+ conductance decrease in che mically stimulated cells that prolongs the duration of spontaneously o ccurring depolarizations to 600-1,700 ms by delaying repolarization. T he freely fluctuating membrane potential shifts to more depolarized le vels, although the total potential range is expanded in the positive a nd negative direction by 5.5 and 3.8 mV, respectively. Chemosensory be havior is explained and discussed with respect to these electrophysiol ogical events.