ゾウリムシの走熱性

抄録

When paramecium cells are placed in a temperature-gradient, they come to the temperature where they have been cultured. In the gradient, those swimming toward the culture temperature show a lower frequency of turning than those swimming away from the culture temperature. Distributions of paramecium cells in the temperature gradient can be explained from the difference in the turning frequency between those ascending and descending the gradient.
Swimming cells sense the temperature gradient as a temporal change of temperature. When the temperature is suddenly dropped from the culture temperature to a lower one, the turning frequency transiently increases and when it is recovered to the culture temperature, the frequency transiently decreases. Following the temperature drop from the culture temperature or recovery to the culture one, the membrane potential transiently depolarizes or hyperpolarizes, respectively. Steep depolarizing spikes are generated at the initial phase of the above depolarization, corresponding to the turning of swimming direction.
Temperature sensitivity is closely related to the adaptation to environmental temperature.