Developmental plasticity of hearing sensitivity in red-eared slider Trachemys scripta elegans

Developmental plasticity of hearing sensitivity (DPHS) has been verified in some groups of vertebrates. Turtles face a trade-off between terrestrial and aquatic hearing in different acoustic environments throughout ontogeny. However, how chelonian hearing sensitivity changes throughout ontogeny is still unclear. To verify DPHS in turtles, auditory brainstem responses (ABR) were compared using hearing thresholds and latencies in female red-eared slider (Trachemys scripta elegans) aged 1 week, 1 month, 1 year, and 5 years, and the results showed hearing sensitivity bandwidths of approximately 200-1100, 200-1100, 200-1300, and 200-1400 Hz, respectively. The lowest threshold sensitivity was approximately 600{square}Hz. Below 600 Hz, ABR threshold decreased rapidly with increasing age (1 week to 1 year), with significant differences between age groups, but no significant difference between the 1- and 5-year age groups (stimulus frequency, 200-600 Hz). Above 600 Hz, ABR threshold was the lowest in the 5-year age group. These findings show that aging was accompanied by hearing sensitivity changes, suggesting rapid, frequency-segmented development during ontogeny. This variability in hearing sensitivity differs from that reported in other vertebrates, and allows adaptation to acoustically distinct environments throughout ontogeny. Our findings further elucidate the developmental patterns of the vertebrate auditory system.