Neurotransmitter and Gut–Brain Metabolic Signatures Underlying Individual Differences in Sociability in Large Yellow Croaker (Larimichthys crocea)

Teleost social behavior plays an important role in foraging, reproduction, and aquaculture management, yet its physiological basis remains poorly understood. This study investigated individual differences in sociability in the large yellow croaker (Larimichthys crocea) using behavioral assays and metabolomic profiling in the brain–intestine axis. Behavioral tests revealed that high-sociability (HS) fish spent significantly more time near conspecifics than low-sociability (LS) fish, indicating clear behavioral divergence between groups. Targeted metabolomics of brain tissue showed distinct neurotransmitter signatures between HS and LS individuals, including significant differences in acetylcholine, DOPAC, xanthurenic acid, and glutamine. Untargeted intestinal metabolomics identified 65 differential metabolites between groups. Intestinal metabolites such as LEA and CEA exhibited significant group-specific variation and were functionally associated with CB1 and CB2 cannabinoid receptors, suggesting a potential endocannabinoid-mediated contribution to sociability differences. Differential metabolites enriched in amino–sugar and nucleotide–sugar metabolic pathways. Integration of behavioral and metabolomic data suggests that neurotransmitter regulation and gut–brain metabolic signaling jointly contribute to sociability differences in large yellow croaker. These findings provide mechanistic insights into social behavior and offer potential biomarkers for welfare assessment and selective breeding in aquaculture.