Efficient high-voltage protection in the electric catfish

Abstract

Starting with the remarkably detailed accounts of the ancient Egyptians (Gamer-Wallert, 1970; Westendorf, 1999), the African electric catfish (Malapteruridae) has been renowned for its ability to generate powerful electric shocks. These are emitted by a specialised electric organ which is composed of a thin layer of electrocytes located directly below the skin that covers nearly the whole body (Fig. 1A,B) (Johnels, 1956). Each electric organ discharge produces a strong monophasic pulse with a duration of 2-3 ms and an amplitude of up to 300 V (Bauer, 1968; Remmler, 1929). Similar to other strongly electric fish, such as the electric eel, electric catfish use their high-voltage pulses as a defensive and offensive weapon (Bennett, 1971). During prey capture, electric catfish emit volleys of electric organ discharges (Fig. 1C) with an initial high-frequency phase (up to 500 Hz) and up to 500 pulses (Bauer, 1968; Belbenoit et al., 1979) that paralyse the muscles of prey fish. These volleys can last for several seconds and stop when the immobilised prey is snapped up and swallowed (Bauer, 1968). Electric catfish are also able to produce brief discharges composed of several high-voltage pulses (Fig. 1D-F) (Ballowitz, 1899; Bauer, 1968) that are thought to be emitted during defensive behaviour