Evidence for a Category of Electroreceptors in the Lateral Line of Gymnotid Fishes
A glass capillary ultramicroelectrode was inserted into the exposed lateral line nerve of otherwise intact Gymnotus and Hypopomus. Spike activity of single fibers was recorded while the fish maintained the normal continuous discharge of the weak electric organs. The only activity in the fibers here reported is a short burst of spikes at 200 to 500 per second, following each discharge (3 to 30 per second) of the electric organ. The number of spikes in a burst changed systematically as conductive objects came near. A small conductive object right over the receptor decreased the number; when the object was just in front of or behind the receptor, it increased the number. Moderate water currents or stroking the skin with a soft brush caused no spikes. It is concluded that these fibers serve as true electroreceptors.