Integrated morphological, histological, physiological, and metabolomic analyses reveal the role of photoperiod in regulating the growth and molting of juvenile Macrobrachium rosenbergii

Photoperiod is a key environmental factor influencing the growth of crustaceans; however, its specific effects and underlying mechanisms on the early growth and molting of juvenile Macrobrachium rosenbergii remain poorly understood. In this study, we investigated the effects of different photoperiods on early growth, molting, and hepatopancreatic metabolism. The results showed that survival rate, weight gain rate, and specific growth rate were significantly higher in the L24:D0 group compared with the L12:D12 and L0:D24 groups. Furthermore, as the duration of light exposure increased, hemolymph levels of 20-hydroxyecdysone (20E) and crustacean hyperglycemic hormone (CHH) also increased significantly (P < 0.05). The expression levels of genes including CHH, ECR, HSP70, MIH, and KRLF were significantly higher in the L24:D0 group than in the other two groups (P < 0.05). Under this condition, 20E content showed a significant positive correlation with RXR and CAN expression levels. Non-targeted metabolomic analysis revealed differential enrichment of ABC transporters, nucleotide metabolism, and the FoxO signaling pathway among treatments. Lipid molecules such as phosphatidylcholine and phosphatidylethanolamine—key metabolites in the glycerophospholipid metabolic pathway—exhibited enhanced metabolism under long photoperiods. These metabolites interacted with one another while simultaneously participating in cellular autophagy, sugar metabolism, and other processes. Mantel test results indicated that juvenile shrimp growth performance and photoperiod were significantly positively correlated with phosphatidylinositol metabolite levels (P < 0.05). These findings provide a solid foundation for elucidating the photoperiod-regulated molting mechanism and for improving the management efficiency of factory-scale aquaculture of M. rosenbergii.