Cutaneous electrical oscillation in a weakly electric fish, Gymnarchus niloticus.

An African electric fish, Gymnarchus niloticus. ceases its electric organ discharge for a prolonged time in response to external electrical signals. During the cessation of electric organ discharges from the electric organ, a weak sinusoidal signal (approximately 0.1 mV cm(-1)) near the fish's previous discharge frequency was recorded near the body. The oscillatory potentials at all points on the body surface were synchronized and had a complex spatial distribution. The source of the potential was determined to be within the dermal tissue. Electroreceptive central neurons that responded to a moving target near the fish with normal electric organ discharges also responded to the same target when the electric organ discharge was interrupted and the potential from the skin existed. This result suggests that the fish may be able to electrolocate objects without the discharge from the electric organ.