Electric pulse characteristics can enable species recognition in African weakly electric fish species

Rebecca Nagel,Frank Kirschbaum,Volker Hofmann,Jacob Engelmann,Ralph Tiedemann

doi:10.1038/s41598-018-29132-z

Abstract

Communication is key to a wide variety of animal behaviours and multiple modalities are often involved in this exchange of information from sender to receiver. The communication of African weakly electric fish, however, is thought to be predominantly unimodal and is mediated by their electric sense, in which species-specific electric organ discharges (EODs) are generated in a context-dependent and thus variable sequence of pulse intervals (SPI). While the primary function of the electric sense is considered to be electrolocation, both of its components likely carry information regarding identity of the sender. However, a clear understanding of their contribution to species recognition is incomplete. We therefore analysed these two electrocommunication components (EOD waveform and SPI statistics) in two sympatric mormyrid Campylomormyrus species. In a set of five playback conditions, we further investigated which components may drive interspecific recognition and discrimination. While we found that both electrocommunication components are species-specific, the cues necessary for species recognition differ between the two species studied. While the EOD waveform and SPI were both necessary and sufficient for species recognition in C. compressirostris males, C. tamandua males apparently utilize other, non-electric modalities. Mapped onto a recent phylogeny, our results suggest that discrimination by electric cues alone may be an apomorphic trait evolved during a recent radiation in this taxon.

Highlights

Communication signals that convey sex and species identity from a sender to a receiver are vital to intraand interspecific recognition and discrimination, often driving reproductive and behavioural isolation[1,2,3]
Hopkins and Bass established that species recognition can be mediated by the electric organ discharge (EOD) and sequence pulse interval (SPI), the two major components of electrocommunication in mormyrid fish
We suggest that while they may be relevant for species recognition and discrimination, the cues mediating recognition may vary depending on species

Summary

Introduction

Communication signals that convey sex and species identity from a sender to a receiver are vital to intraand interspecific recognition and discrimination, often driving reproductive and behavioural isolation[1,2,3]. A wide range of SPI patterns observed at short timescales (e.g., bursts, cessations, and/or regularizations of approximately 20 inter-pulse-intervals) have been defined and linked to specific behavioural contexts[14,27]. Notwithstanding this large body of research addressing numerous aspects of mormyrid electrocommunication, a clear understanding of the contribution of the two major electrocommunication components (EOD waveform and SPI) for species recognition has not yet been achieved (but see ref.[23] for experiments with the sound producing mormyrid Pollimyrus isidori). We investigate the contributions of these components in two African weakly electric fish species, Campylomormyrus compressirostris and Campylomormyrus tamandua

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