# Structural Rearrangement of the Olfactory Epithelium in Male Baikal Yellowfin Sculpins Across the Reproductive Period

## TL;DR

Male yellowfin sculpins undergo structural changes in their olfactory system during spawning to better detect female pheromones.

## Contribution

The study reveals structural rearrangements in the olfactory epithelium of male yellowfin sculpins linked to reproductive behavior.

## Key findings

- Structural changes in olfactory epithelium cells occur during spawning to enhance pheromone reception.
- Fish shift sensitivity from food signals to sex pheromones during reproductive periods.
- Peripheral olfactory system plasticity contributes to complex animal behavior.

## Abstract

The molecular mechanisms of animal behavior directed with smell signals is one of the most enigmatic subjects in modern neurobiology. The most convenient model for research is the reproductive motivation of spawning different fishes when they lose the capability to react on the feed signals, stop feeding, and simultaneously acquire high sensitivity to the sex pheromones. The results of the present work show that, in the spawning period, in the olfactory epithelium cells of Baikal endemic male fish yellowfin sculpin, the ultrastructural rearrangements for adaptation to the reception of sex pheromones of females occur. This is essential for the effective attraction of spawning partners and for successful egg fertilization. The obtained data reveal that the complex behavior of animals is directed not only by central nervous system activity, but also by structural adjustments of the peripheral part of the olfactory analyzer.

The morphological peculiarities of receptor neurons and support cells in the olfactory epithelium of male yellowfin sculpin (Cottocomephorus grewingkii; Dybowski, 1874) were studied during the pre-spawning, spawning (when males do not feed and have a higher sensitivity to female pheromones), and guarding (the fertilized eggs) periods. This study was performed using electron transmission and laser confocal microscopy. Structural changes in the fish olfactory epithelium are associated with the shift in olfactory signals from alimentary to pheromonal. These results expand our knowledge of the odorant-dependent plasticity of the periphery of the fish olfactory system.