Hearing threshold and frequency discrimination in the purely aquatic frog Xenopus laevis (pipidae): Measurement by means of conditioning

Hearing threshold and frequency discrimination for underwater sound were me asured in the clawed frog Xenopus laevis by means of conditioning. A go/no go discrimination procedure was used in which the test tone was presented c oncurrently with a wave on the surface of the water. The tone signalled whe ther or not the frog should respond to the wave. The hearing range of X. la evis was 200-4000 Hz, Similar thresholds of 92-96 dB re 1 mu Pa were found at 600 Hz, 1400-1800 Hz and 3200-3600 Hz. A high threshold at 1000-1300 Hz suggested that this was the frequency range between the sensitivities of th e amphibian and basilar papillae, Relative frequency discrimination was app roximately 5 % at 400-800 Hz, 45 % at 1000 Hz and 2.4-6 % at 1600-2500 Hz. This last range encompasses the dominant frequencies of the advertisement c all of this species. High discrimination acuity at these frequencies may be used in distinguishing between calling males, The threshold for a one-thir d-octave bandpass noise centred at 600 Hz was 27.6 dB lower than that for a pure tone of 600 Hz, suggesting that sound intensity was integrated within this bandwidth, possibly by a critical-band mechanism.