Experimental Evidence of Geomagnetic Orientation in Elasmobranch Fishes

Abstract

Marine sharks, skates, and rays are endowed with an electric sense that enables them to detect voltage gradients as low as 0.01 ~V/cm within the frequency range of direct current (DC) up to about 8 Hz. Their electroreceptor system comprises the ampullae of Lorenzini, which are delicate sensory structures in the snouts of these elasmo-branch fishes. Sharks, skates, and rays use their electric sense in predation, sharply cueing in on the DC and low-frequency bioelectric fields of their prey. Swimming through the earth's magnetic field, they also induce electric fields that may provide them with the physi-cal basis of an electromagnetic compass sense. Their ability to orient magnetically has in fact been demonstrated in recent training ex-periments.