# Potential Physiological and Molecular Mechanisms Underlying Low Viability of Gynogenetic WW-Type Super-Female Sterlet (Acipenser ruthenus)

## TL;DR

This study explores why WW-type super-female sterlet sturgeon have low survival rates, finding issues with oxidative stress and gene expression linked to metabolism and cell death.

## Contribution

The study provides integrative physiological and transcriptomic evidence for the poor viability of WW-type super-female sterlet.

## Key findings

- WW-type super-female sterlet had a significantly lower survival rate (64.2%) compared to ZZ and ZW types (94.2%).
- WW-type fish showed higher MDA and GSH-Px levels, indicating increased lipid peroxidation and inadequate antioxidant response.
- Transcriptomic analysis revealed 747 differentially expressed genes in WW-type fish, with disrupted arachidonic acid metabolism and ferroptosis activation.

## Abstract

WW-type super-female broodstock are essential for all-female breeding in sturgeons under the ZZ/ZW sex-determination system, but their practical use is constrained by high mortality. This study investigates the underlying physiological and molecular mechanisms contributing to the reduced viability of WW-type super-female sterlet (Acipenser ruthenus) by comparing three genotypes (ZZ, ZW and WW) in terms of survival rates, oxidative stress levels, and gonadal gene expression. F2 gynogenetic diploid juvenile sterlet with three genotypes were reared for 100 days under controlled conditions. Survival rates were recorded, and oxidative stress markers, including SOD, CAT, MDA and GSH-Px, were measured using commercially available assay kits. Gonadal gene expression profiles were analyzed using transcriptomic analysis. The results revealed that WW-type juveniles exhibited a significantly lower survival rate (64.2%) compared to ZZ-type and ZW-type fish (both 94.2%, p < 0.0001). While hepatic SOD and CAT activities did not differ among genotypes, MDA and GSH-Px levels were significantly higher in WW-type fish, suggesting enhanced lipid peroxidation and an insufficient compensatory antioxidant response. Transcriptome analysis revealed 747 significantly differentially expressed genes between WW-type super-females and normal ZZ/ZW individuals (p < 0.05), with significant enrichment in pathways related to immune regulation, receptor activity, lipid metabolism, and ferroptosis. Notably, downregulation of arachidonic acid metabolism genes (PTGS2, PTGES, PTGDS) was observed, while ferroptosis-related genes GPX4 and SLC3A2 were upregulated, suggesting that disturbed arachidonic acid metabolism, along with lipid peroxidation and ferroptosis activation, contribute to the reduced survival of WW-type super-females. These findings provide integrative physiological and transcriptomic evidence for the mechanistic basis of poor fitness in gynogenetic WW-type super-females and offer foundational data for improving the feasibility of all-female breeding in sturgeon.