Auditory sensitivity changes with diurnal temperature variation in little torrent frogs (Amolops torrentis)

Temperature fluctuation affects physiology and behaviour in ectotherms. Previous studies revealed that the phonotactic preference of female frogs was affected by temperature fluctuations; however, the corresponding plasticity of peripheral auditory sensitivity is unclear. In the present study, the auditory sensitivity of little torrent frogs (Amolops torrentis) was tested by auditory brainstem responses (ABRs) in both natural warm and cold conditions. The threshold and latency of the ABRs evoked by tone pips ranging from 1.0–7.0 kHz and clicks were compared between these two conditions. The results showed that ABR thresholds were higher and latencies were longer at cold compared to those at warm temperatures for relatively low frequencies (1.8–2.6 kHz), while no significant differences existed at relatively high frequencies (3.0–7.0 kHz). Our previous study showed that the best hearing frequency range of the little torrent frog is 1.6–2.0 kHz, whereas females behaviourally prefer higher frequencies (4.3 kHz). These results indicate that temperature fluctuations in natural habitats can change auditory sensitivity around the best hearing range (1.6–2.0 kHz), while they do not affect the female-preferred frequency range (4.3 kHz). Our results demonstrate that auditory frequency sensitivity exhibits diurnal temperature-dependent plastic changes, which may be adaptive for diurnal reproductive behaviour in this species.