# Reproductive state-dependent cell turnover in the inner ear of the plainfin midshipman fish (Porichthys notatus)

## TL;DR

This study explores how the inner ear of plainfin midshipman fish changes during breeding seasons, revealing differences in cell turnover between males and females.

## Contribution

The study identifies reproductive state-dependent cell turnover in the inner ear of plainfin midshipman fish, highlighting sex-specific and region-specific mechanisms.

## Key findings

- Reproductive type I males show reduced saccular cell proliferation without increased cell death during breeding.
- Summer females exhibit increased saccular cell proliferation with no seasonal changes in other inner ear regions.
- Cellular plasticity in the midshipman inner ear is linked to seasonal auditory sensitivity changes.

## Abstract

Plainfin midshipman fish (Porichthys notatus) exhibit seasonal auditory plasticity that enhances their reproductive success. During the summer, type I male midshipman acoustically court females and both the males and females exhibit increased auditory sensitivity during this period. The enhanced auditory sensitivity is associated with increased density of sensory hair cells in the saccule but not the utricle, suggesting that different mechanisms underlie physiological plasticity in distinct inner ear regions. To better understand how shifts in hair cell number occur within auditory tissues, we examined cell turnover across breeding states and sexes in midshipman fish. We found that reproductive type I males exhibited less saccular cell proliferation than non-reproductive males without a change in cell death, indicating a net loss of saccular cells during the breeding season. By contrast, saccular cell proliferation increased in summer females, with no seasonal changes in other inner ear epithelia. Collectively, our data reveal that multiple mechanisms are likely to contribute to seasonal auditory plasticity within a single species, potentially within the ear of an individual animal.

Summary: Quantification of cell division and cell death in the inner ears of type I male and female midshipman fish reveals cellular plasticity in the midshipman inner ear.