[The behavioral reactions of fresh-water crayfish to sensory exposures: the motor components].

Responses to some distant stimuli which acted on the mechanosensory and visual systems and were close to natural ones were investigated in native crayfish Astacus astacus and reared in aquaria American crayfish Procambarus cubensis. The stimuli did not evoke immediate animal movements, however they induced short-latency EMG reactions in walking leg and abdominal muscles as well as long-term changes in the background locomotor activity. Considerable non-specificity of the so-called indifferent stimuli was mentioned as well as dependence of the behavioural reactions on the animal functional state. The results taken together with the previous ones concerning crayfish autonomous responses to the same stimuli allow us to suggest a considerable similarity of the responses to relatively neutral sensory stimuli in higher crustaceans and higher vertebrates.