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Journal of Experimental Biology 164,39-53 (1992)
Published by Company of Biologists 1992

MEMBRANE POTENTIAL RESPONSES TO THERMAL STIMULATION AND THE CONTROL OF THERMOACCUMULATION IN PARAMECIUM CAUDATUM

TAKASHI TOMINAGA 1 and YUTAKA NAITOH 2

1 Institute of Biological Sciences, University of Tsukuba Tsukuba 305, Japan
2 Institute of Biological Sciences, University of Tsukuba Tsukuba 305, Japan; Present address: JSPS Bonn Liaison Office, ‘Bonn-Center’, H 1104, Bundeskanzelerplatz 2-10, 5300 Bonn 1, FRG

1. The overall membrane potential response of the ciliate Paramecium caudatum to a rise in the temperature of its environment was depolarizing when the ambient temperature before stimulation (Te) was equal to or higher than the culture temperature (Tc), but hyperpolarizing when Te was lower than Tc.

2. The anterior region of the cell responded to a rise in temperature with a localized membrane depolarization. The posterior region was depolarized when Te was equal to or higher than Tc but hyperpolarized when Te was lower than Tc. The Te-dependent polarity reversal of the posterior response was responsible for the comparable reversal of the overall response.

3. The temperature at which the polarity reversal of the posterior response took place shifted according to Tc. This shift caused a comparable shift in the temperature at which polarity reversal occurred for the overall response.

4. The Te-dependent polarity reversal of the posterior response and its Tc-dependence are major causes of thermoaccumulation mediated by ciliary activity of Paramecium in regions with temperatures close to Tc

Key words: thermoreceptor potential, thermoaccumulation, Paramecium caudatum

Accepted on November 26, 1991






© The Company of Biologists Ltd 1992