Ontogenetic development of hearing sensitivity to airborne sound in the female red-eared slider, Trachemys scripta elegans.

Ontogenetic development of hearing sensitivity has been verified in many groups of vertebrates, but not turtles. Turtles exhibit sexual dimorphism in hearing. To examine the development of hearing in female turtles, auditory brainstem responses (ABR) were compared by assessing the hearing-sensitivity bandwidth, ABR threshold, and latency of female Trachemys scripta elegans aged 1 week, 1 month, 1 yr, and 5 yr. The hearing-sensitivity bandwidths were 0.2–1.1, 0.2–1.1, 0.2–1.3, and 0.2–1.4 kHz in each age group, respectively. Below 0.6 kHz, the ABR threshold decreased from the 1-week to 1-yr age group, with a significant difference between age groups. No significant difference was detected between the 1- and 5-yr age groups (within a stimulus frequency of 0.2–0.6 kHz). Above 0.6 kHz, ABR thresholds decreased significantly from the 1-yr to 5-yr age group (within a stimulus frequency of 0.7–1.0 kHz). There was no significant difference between the 1-month and 1-yr age groups (within a stimulus frequency of 0.7–1.0 kHz), or between the 1-week and 1-month age groups (within a stimulus frequency of 0.7–1.0 kHz, except 0.9 kHz). Thus, female turtle hearing shows frequency-segmented development.