Effect of temperature acclimation in the crayfish Astacus astacus L. on the locomotor activity during a cyclic temperature change

1. 1.|The thermal dependence of the locomotor activity of 5°C- and 20°C-acclimated crayfish ( Astacus astacus L.) was studied using a cyclic temperature change (0.3°C/min) at 4-23-4°C. 2. 2.|The thermal dependence of the locomotor activity rate of the 5°C-acclimated crayfish showed hysteresis between 5 and 14°C; activity being higher during cooling than during warming. In the 20°C-acclimated animals, no hysteresis in the thermal dependence of locomotor activity was observed. 3. 3.|In both acclimation groups the locomotor activity rate was inversely related to temperature between 7 and 23°C, irrespective of the direction of the temperature change. 4. 4.|During warming from 9 to 19°C, the 20°C-acclimated crayfish were more active than the 5°C-acclimated ones. 5. 5.|At the lowest temperatures (4–6°C), inactivity related to chill coma was observed in the warm-acclimated crayfish.