[The orienting reaction in invertebrates].

There are described the changes in movement and autonomous activity of the freshwater crayfish upon the sudden changes of the environment. The judging the reaction was based on: 1) the observation of all available behavioral manifestations in the crayfish Procambarus cubensis which has been in its "natural" habitat; 2) the recording of the electrical activity of the heart (ECG) and of the ventilatory appendages (scaphognathites; SGG) in freely moving Astacus astacus and Procambarus cubensis; 3) the non-invasive recording of Procambarus cubensis background locomotion in the conditions close to natural ones. It was concluded that even being immobile crayfish is continuously watching its surrounding and is revealing its very slight changes. It is suggested that crayfish response to "neutral" stimulus arising in the environment is rather similar to the orienting response of higher mammals. It is possible to suggest too the appearance in this situation of the emotional reaction in the crayfish.