Cyclic AMP-regulated opposing and parallel effects of serotonin and dopamine on phototaxis in the Marmorkrebs (marbled crayfish).

Phototactic behaviours are observed from prokaryotes to amphibians and are a basic form of orientation. We showed that the marbled crayfish displays phototaxis in which the behavioural response reversed from negative to positive depending on external light conditions. Animals reared in a 12-L/12-D light cycle showed negative phototaxis during daytime and positive phototaxis during night-time.