This study investigated the pattern of the electrical field potentials recorded near the prebranchial chamber of the native crayfish Astacus leptodactylus. Inside the prebranchial chamber, the electrical waves had maximal amplitude and showed 2–4 peaks per cycle. Potentials with the same frequency but smaller amplitude and simpler shape were also recorded outside the chamber, near the edge of the carapace, and at some distance towards the caudal direction. Correlation of these electrical potentials with movements of the scaphognathite in intact Procambarus cubensis with a transparent external wall of the prebranchial chamber has shown a high coincidence both in rate and phase of the two processes. The electrical activity picked up by an electrode located in the prebranchial chamber or near it represents the cumulative electrical field generated by the muscles moving the scaphognathite, and may be termed as the electroscaphognathitegram (ESG). The correlation of the mechanoscaphognatitegram determined optically from the magnified image of the scaphognathite and the ESG allowed us to suggest that the ascending phase of single electrical wave corresponds to the activation of the muscles responsible for downward movement of the scaphognathite, whereas its descending phase reflects its upwards movement.