Further analysis of sensory coding in electroreceptors of electric fish.

A new category of sensory transducers, electroreceptors, was to be inferred from the work of Lissmannl and Lissmann and Machine2,3 and was directly demonstrated by Hagiwara et al.,4−8 Szabo and Fessard,9,10 and Szaboll in electric fish. Three fresh-water families, the Gymnotidae from tropical America and the Gymnarchidae and Mormyridae from tropical Africa, with many species, all discharge low-voltage pulses from small electric organs more or less continuously into the water, apparently useful in detecting objects, cavities, other fish, and as social signals to each other. The diversity of form of discharge is important. Some gymnotids and perhaps all mormyrids discharge at low (ca. 0–5/sec), irregular frequencies, rising (to 30–100/sec) with excitement. Other gymnotids and the only known gymnarchid discharge at high (300–>1000/sec), regular, species-characteristic, and nearly invariant frequencies. Several gymnotids are intermediate, including the subject of this communication.