Electric discharges and electrogenesis peculiarity in two African upside-down catfishes, Synodontis caudovittatus and S. eupterus (Mochokidae, Siluriformes)

Abstract

The paper reports spontaneous generation of weak electric discharges with an amplitude of 0.4–1.0 mV and a frequency of 3–9 min^–1 by solitary Synodontis caudovittatus fish. When fish individuals were tested in pairs, their aggressive–defense interactions were associated with an increase in the amplitude of the discharges (up to 30–45 mV) compared to the discharges of individual fish, while the duration of the pulses increased up to 20–25 ms due to the prolongation of the second phase. In S. eupterus, electric activity was recorded only in the course of aggression–defense interactions, while spontaneous generation of discharges was not observed at all. The paper discusses the different aspects of electrocummunication between the catfish including the role of the reversion of polarity of the merged summated discharges with increased duration.