Electrical and behavioral courtship displays in the mormyrid fish Brienomyrus brachyistius

Abstract

Mormyrid electric fish rely on the waveform of their electric organ discharges (EODs) for communicating species, sex, and social status, while they use the sequences of pulse intervals (SPIs) for communicating rapidly changing behavioral states and motivation. Little is known of electric signaling during courtship behavior because of two major difficulties: (1) the fish are not easily bred in captivity and (2) there is no reliable means of separating electric signals from several individuals in natural communication settings. Through simulating artificial rain conditions, we have successfully induced courtship and succeeded in breeding a mormyrid electric fish (Brienomyrus brachyistius) in the laboratory. We have also developed a system of video recording and editing combined with cross correlation analysis to precisely record and view behavior and separate EODs from two individuals in non-breeding and breeding contexts. Knowing the electrical and motor patterns during courtship allows for further exploration of topics such as mate choice and neural basis of pattern generation in these fish. Here we describe nine common motor displays and 11 SPIs. Analysis of frequency of occurrences suggests that some SPI patterns are sex and season specific. We also observed electrical duetting called ;rasp matching' during courtship signaling among pairs; males and females exchange ;rasps' and ;bursts', respectively, in alternation. Our study employs new techniques to separate and document SPIs in the context of courtship. We show that some SPIs correlate with specific behavioral acts around the time of spawning.