[Magnetic field perception by the electroreceptor system of fish]

Responses of 40 neurons in the acoustic-lateral area to electrical stimuli and changing magnetic induction were studied in the Black Sea skates Dasyates (Trigon) pastinaca. The smallest magnetic induction change which caused a response was 0.8 Gs/s, proving the possibility of perception of the geomagnetic field by electroreceptors of a slow-moving fish. Opposite reactions to magnetic stimulation were observed in neurons responding to electrical stimuli in the same way but connected with receptors of the right and left sides of the fish. Short-circuiting between the inner medium of the fish and the sea water showed that the induction current circuit is isolated from the inner medium and, apparently, formed by the ampullary canals.