Phase locking and phase avoidance behavior in eleven Nilotic mormyrid species (Mormyridae, Mormyriformes) in response to external electric stimuli

Abstract

Latency-dependent responses to artificial electric stimuli in 11 species of the Nilotic mormyrids were studied. In total, more than 350 poststimulus time histograms from 132 individuals were analyzed. All species studied exhibited the latency-dependent responses. Both main types of responses – phase locking and phase avoidance behavior or the preferred latency response (PLR) and preferred latency avoidance (PLA) – were found in eight species (Brevimyrus niger, Hippopotamyrus pictus, Marcusenius cyprinoides, Mormyrus kannume, M. hasselquistii, Petrocephalus bane, P. bovei and ‘Pollimyrus’ petherici), while only PLR were recorded from the remaining three species (Hyperopisus bebe, Mormyrops anguilloides and Mormyrus caschive). In eight species both types of behavior were found in fish of the same sex. In four species both types of behavior were found both in females and males. Finally, in four species both types of behavior were revealed in the same individual (in total, there were eight such individuals). In some individuals of different species the atypical responses with substantially increased latencies (compared to the typical PLR and PLA) were observed. The possible role of the phase locking and phase avoidance behavior in the mormyrid electrolocation and communication is discussed.