Comparative Proteomic Analysis of Gonadal Tissue in <em>Solea senegalensis </em>Reveals Reproductive Deregulation Associated with F1 Individuals

Reproductive dysfunction in captive-bred Senegalese sole (Solea senegalensis) limits the consolidation of its aquaculture production, particularly due to reduced fertility and poor sperm quality in F1 males. To elucidate the molecular mechanisms underlying this problem, a quantitative proteomic analysis was conducted on gonadal tissues from wild and F1 males and females using LC–MS/MS. A total of 2,221 proteins were identified, of which 1,797 were retained after quality filtering. Comparative analyses revealed a clear segregation by origin (F1 (cultivated) and wild) and sex (male and female), and 86 proteins were differentially expressed between F1 and wild males. Functional enrichment showed a significant downregulation of key reproductive processes in F1 males, including sperm–egg recognition, binding of sperm to zona pellucida, and acrosome reaction, suggesting impaired gamete interaction and fertilization ability. Conversely, F1 males displayed enrichment of metabolic and proteolytic pathways, indicative of compensatory energy demands. Protein–protein interaction network analysis identified a reproductive subnetwork dominated by zona pellucida sperm-binding proteins, which exhibited reduced connectivity in F1 males. These results demonstrate a coordinated suppression of molecular components essential for sperm–egg communication and acrosomal exocytosis, providing proteomic evidence for a systemic deregulation of the reproductive machinery in F1 fish. This study identifies potential protein biomarkers linked to reproductive performance, offering molecular targets to improve broodstock management and fertilization success in S. senegalensis aquaculture.