Thermal acclimation without heat shock, and motor responses to a sudden temperature change in Asellus aquaticus

Abstract

1. In the fresh water isopod Asellus aquaticus the critical thermal maximum (CTMax) after 2 weeks was similar in animals transferred directly from 9°C to 22°C and in animals acclimated gradually (1°C/day). 2. A sudden change of ambient temperature caused immediate changes in the locomotor behaviour of Asellus that did not persist, and especially an increase of the frequency and angle of turning (klinokinesis). 3. Asellus, acclimated to 12°C, preferred temperatures of 11–15°C in a thermal gradient, and showed klinokinetic heat avoidance reactions at effective heat shock temperature (28°C).