The relevance of temporal cues in a fish sound: a first experimental investigation using modified signals in cichlids

International audiencePlayback experiments have been a useful tool for studying the function of sounds and the relevance of different sound characteristics in signal recognition in many different species of vertebrates. However, successful playback experiments in sound-producing fish remain rare, and few studies have investigated the role of particular sound features in the encoding of information. In this study, we set-up an apparatus in order to test the relevance of acoustic signals in males of the cichlid Metriaclima zebra. We found that territorial males responded more to playbacks by increasing their territorial activity and approaching the loudspeaker during and after playbacks. If sounds are used to indicate the presence of a competitor, we modified two sound characteristics, that is, the pulse period and the number of pulses, in order to investigate whether the observed behavioural response was modulated by the temporal structure of sounds recorded during aggressive interactions. Modified sounds yielded little or no effect on the behavioural response they elicited in territorial males, suggesting a high tolerance for variations in pulse period and number of pulses. The biological function of sounds in M. zebra and the lack of responsiveness to our temporal modifications are discussed

Sounds of shallow water fishes pitch within the quiet window of the habitat ambient noise

The habitat ambient noise may exert an important selective pressure on frequencies used in acoustic communication by animals. A previous study demonstrated the presence of a match between the low-frequency quiet region of the stream ambient noise (termed 'quiet window') and the main frequencies used for sound production and hearing by two stream gobies (Padogobius bonelli, Gobius nigricans). The present study examines the spectral features of ambient noise in very shallow freshwater, brackish and marine habitats and correlates them to the range of dominant frequencies of sounds used by nine species of Mediterranean gobies reproducing in these environments. Ambient noise spectra of these habitats featured a low-frequency quiet window centered at 100 Hz (stream, sandy/rocky sea shore), or at 200 Hz (spring, brackish lagoon). The analysis of the ambient noise/sound spectrum relationships showed the sound frequencies matched the frequency band of the quiet window in the ambient noise typical of their own habitat. Analogous ambient noise/sound frequency relationships were observed in other shallow-water teleosts living in similar underwater environments. Conclusions may be relevant to the understanding of evolution of fish acoustic communication and hearing