Electrogenesis in Two African Upside-Down Catfishes, Synodontis sorex and S. batensoda (Mochokidae, Siluriformes).

Weak electric discharges generated by the two species of the African upside-down catfishes, Synodontis sorex and S. batensoda are described. In both species two types of discharges were recorded in the course of aggressive-defense interactions in the pairs of individuals: short simple biphasic and longer (duration >20 ms) discharges with more complex waveform. The discharges of the latter type seem to result from a temporal summation (with various latency) of simple discharges. It is suggested that formation of the long quasimonopolar discharges enhances the coincidence of frequency spectrum of the catfish discharges with maximum sensitivity range of their ampullary electroreceptors.