Based on studies of a few specialist species (otophysans), the gasbladder is believed to aid in fish audition by transferring pressure components of incoming sound to the ears. We examined the gasbladder's auditory role in goldfish Carassius auratus, an otophysan, and two generalists: the blue gourami Trichogaster trichopterus and oyster toadfish Opsanus tau. Audiograms were obtained with the acoustically evoked potential protocol. X-rays were used to locate the gasbladder, air was withdrawn with a syringe, and tuning curves were obtained from gas-filled and then deflated fish. In goldfish, with Weberian ossicles linking the gas bladder and inner ears, thresholds increased by 33-55 dB (frequency dependent) after deflation. In blue gourami and toadfish, however, thresholds and evoked potential waveforms did not change. These results indicate a variable role for the gasbladder in fish audition and suggest that it may not serve an auditory function in typical teleosts
Abstract: