# Peripheral hearing sensitivity is similar between the sexes in a benthic turtle species despite the larger body size of males

## TL;DR

This study found that male and female Chinese softshell turtles have similar hearing sensitivity despite males being larger, challenging the idea that larger body size always correlates with better hearing.

## Contribution

The study provides new data on hearing sensitivity in a benthic turtle species, showing no sexual dimorphism despite male size advantage.

## Key findings

- Both sexes of Chinese softshell turtles have a hearing sensitivity bandwidth of 0.2–0.9 kHz.
- No significant differences in auditory brainstem response thresholds or latencies were found between male and female turtles.
- Sexually dimorphic hearing sensitivity is not present in Pelodiscus sinensis, suggesting unique physiological or environmental adaptations.

## Abstract

Sexually dimorphic hearing sensitivity has evolved in many vertebrate species, and the sex with a larger body size typically shows more sensitive hearing. However, generalizing this association is controversial. Research on sexually dimorphic hearing sensitivity contributes to an understanding of auditory sense functions, adaptations, and evolution among species. Therefore, the hypothesized association between body size and hearing needs further validation, especially in specific animal groups. In this study, we assessed hearing sensitivity by measuring auditory brainstem responses (ABRs) in both sexes of 3‐year‐old Chinese softshell turtles (Pelodiscus sinensis). In this species, male bodies are larger than those of female, and individuals spend most of their lives in the mud at the bottom of freshwater habitats. We found that for both sexes, the hearing sensitivity bandwidth was 0.2–0.9 kHz. Although males were significantly larger than females, no significant differences in ABR thresholds or latencies were found between males and females at the same stimulus frequency. These results indicate that P. sinensis hearing is only sensitive to low‐frequency (typically <0.9 kHz) sound signals and that sexually dimorphic hearing sensitivity is not a trait that has evolved in P. sinensis. Physiological and environmental reasons may account for P. sinensis acoustic communication via low‐frequency sound signals and the lack of sexually dimorphic hearing sensitivity in these benthic turtles. The results of this study refine our understanding of the adaptation and evolution of the vertebrate auditory system.

In this study, we assessed sex‐based differences in body size and hearing sensitivity in Chinese softshell turtles (Pelodiscus sinensis). Studies on chelonian hearing are limited. We believe that our study makes a significant contribution to the literature because, although an association because body size and sexually dimorphic differences in auditory sensitivity of vertebrates has been reported, we found no such association in this study. Our results provide additional data to better understand the evolution and adaptation of vertebrate auditory systems.