Effects of noise exposure on hearing and sound production in Trichopsis vittata (Pisces; Anabantoidei) [abstract]

Nicola Novarini, Tomonari Akamatsu & Hong Y. Yan (2002). Effects of noise exposure on hearing and sound production in Trichopsis vittata (Pisces; Anabantoidei) [abstract]. Bioacoustics, Volume 13 (2): 203 -204

Little information exists about how noise exposure may modulate agonistic behaviour of some sonic fish in which perception of sounds produced by conspecifics is crucial in interpreting the message conveyed by the opponents. Recently, it has been demonstrated that temporary hearing impairment can be induced by exposing fish to certain periods of white noise. Experiments were designed to test the hypothesis that elevation of hearing thresholds my means of exposure to noise) of a sonic fish, the croaking gourami Trichopsis vittata, could alter the quality of sound produced because of the altered feedback route in sound perception and production loop. This experiment also tested the hypothesis that altered characteristics of the sound produced would subsequently modulate the outcome of the behavioural contest. Test subjects were exposed to 300 - 4000 Hz white noise (142 dB; re: 1 mPa) for 12 and 24 hours, respectively. The hearing threshold shifts were evaluated at the end of noise exposure as well as one day and five days after exposure with the use of the auditory brainstem response recording protocol. The frequency range tested (600 - 2500 Hz) corresponded to the fish best hearing range as well as to the range of the croaking sounds emitted by the fish. Hearing threshold was found significantly elevated after noise exposure. Recovery, however, appeared faster in 12-hr noise exposed fish than those from the 24-hr exposure group. The croaking sounds produced by noise-exposed fish were also recorded through staged contests. The results were used to compare with the sounds produced prior to the exposure. Details of differences in sound spectra as well as changes of agonistic behaviour are presented and discussed (supported by National Organization for Hearing Research, NIMH-58198, Institute of Museum and Library Service-LL90187).