AUDITORY THRESHOLD OF MARBLED SOLE PLEURO NECTES YOKOHAMAE

The auditory thresholds for 10 specimens of the marbled sole Pleuronec tes yokohamae were determined by heartbeat conditioning using pure ton e stimuli of 9 frequencies from 60 to 1,000 Hz, which. were coupled wi th an electric shock. The marbled sole could hear sound in the frequen cy range from 60 to 1,000 Hz, and the lowest threshold was 92.5 dB re 1 mu Pa at 100 Hz. Hearing ability declined rapidly with increasing fr equency above 300 Hz, but little difference occurred in hearing abilit y between 400 and 500 Hz. The results show that the auditory threshold s of marbled sole are higher and its sensitive frequency range is narr ower than that for fish that have swimbladder.