Proteomic Characterization of the Salivary Microenvironment Associated with Mouthbrooding in Nile Tilapia (Oreochromis niloticus)

Mouthbrooding is a specialized parental care strategy that enhances offspring survival in many cichlid fishes; however, the molecular characteristics of the maternal buccal environment remain poorly understood. In this study, we compared embryonic performance between artificial incubation and natural mouthbrooding in Nile tilapia (Oreochromis niloticus) and characterized the buccal fluid proteome associated with mouthbrooding using LC–MS/MS-based proteomics. Naturally mouthbrooded embryos exhibited significantly higher survival rates and lower morphological abnormality rates than artificially incubated embryos. Proteomic analysis revealed extensive remodeling of buccal fluid protein composition during mouthbrooding and identified numerous differentially abundant proteins among mouthbrooding females, pre-mouthbrooding females, and males. Functional enrichment analyses showed that mouthbrooding-associated proteins were predominantly involved in immune regulation, epithelial organization, and host–pathogen interaction pathways. Proteins enriched during mouthbrooding were mainly associated with epithelial barrier maintenance and immune defense functions. These findings suggest that mouthbrooding females establish a distinct buccal microenvironment that may contribute to embryonic survival and developmental success. This study provides new insights into the molecular basis of parental care in mouthbrooding fishes and offers potential targets for improving artificial incubation strategies in tilapia aquaculture.