Why the brown ghost chirps at night

Abstract

AbstractSince the pioneering work by Moeller, Szabo and Bullock, weakly electric fish have been widely used as a model to approach the study of both spatial and social cognitive abilities in a vertebrate taxon typically less approachable than mammals or other terrestrial vertebrates. Through their electric organ, weakly electric fish generate low-intensity electric fields around their bodies with which they scan the environment to orient themselves and interact with conspecifics even in complete darkness. The brown ghost knifefish is probably the most intensely studied species due to the large repertoire of individually variable and sex-specific electric signals it produces. Their rich electric vocabulary is composed of brief frequency modulations - orchirps- of the oscillating dipole moment emitted continuously by their electric organ. Chirps of different types are thought to convey very specific and behaviorally salient information, and are thus used as references to specific internal states during recordings - of either the brain or the electric organ - or during behavioral observations. However, while this notion undoubtedly contributed to the success of this model in neuroethology during the past seven decades, the logic underlying this electric communication still remains unclear.This study re-evaluates this view in the attempt to provide an alternative, and perhaps complementary, explanation for why these freshwater bottom dwellers emit electric chirps. By revealing correlations between chirping, electric field geometry and detectability in enriched environments, we provide evidence for a previously unexplored role of chirps as specialized self-directed signals used to expand conspecific electrolocation ranges during social encounters.