CIRCADIAN LOCOMOTOR-ACTIVITY AND ITS ENTRAINMENT BY FOOD IN THE CRAYFISH PROCAMBARUS-CLARKI

The aim of our experiments has been to study the effect of light and f ood in the locomotor activity rhythm of the crayfish Procambarus clark i. Experiments were carried out under light:dark (LD) cycles of 12h:12 h, under continuous darkness (DD) and under continuous light (LL). Und er LD cycles, two peaks of activity were observed during the night pha se of the cycle, while resting was characteristic of the day phase. Un der DD or LL, it was possible to follow a free-running rhythm with a p eriodicity of 22.3+/-0.84 h in DD and 24.8+/-0.27 h in LL, typical of circadian rhythms of nocturnal species. A single delivery of food in t he day phase of the LD cycle resulted in an outburst of locomotor acti vity that lasted for several hours. In the ensuing days, an activity p eak appeared in phase with the time of food delivery. The food-related activity peak could be followed for up to 2 weeks without food reinfo rcement. Under DD and LL, food induced an activity rhythm in previousl y arrhythmic animals. Here the period was longer than 24 h in DD (26.2 +/-0.12 h) and shorter in LL (22.5+/-0.46 h). Together, these results strongly suggest that light and food may play a role entraining a loco motor activity rhythm in crayfish.