Effects of Different Diets on Growth and Immunity in Juvenile Portunus trituberculatus

Portunus trituberculatus is an economically important marine crab species in China. Short-term nutritional conditioning during the juvenile stage may improve their physiological readiness before release. This study compared the effects of four dietary treatments on the growth, antioxidant capacity, immune function, and hepatopancreatic transcriptome of juvenile P. trituberculatus. A 4-week feeding trial compared a commercial pelleted diet (Treatment C) with three natural marine diets: Larimichthys crocea (Treatment Y), Litopenaeus vannamei (Treatment X), and Ruditapes philippinarum (Treatment B). The results demonstrated that Treatments X and B exhibited optimal growth performance, with significantly higher weight gain rate (WGR) and specific growth rate (SGR) than Treatments Y and C (p < 0.05). Regarding immune and antioxidant functions, Treatment X showed significantly enhanced parameters, including total antioxidant capacity (T-AOC) and activities of superoxide dismutase (SOD) and catalase (CAT), as well as contents of reduced glutathione (GSH) and lysozyme (LZM), all of which were markedly higher than those in Treatment C (p < 0.05). Transcriptomic analysis further revealed the molecular mechanisms underlying these physiological enhancements. Compared to the control, Treatment X exhibited significant enrichment in immune-related pathways, specifically the phagosome and gap junction signaling pathways. Notably, key cytoskeleton-related genes (tubulin alpha chain and tubulin beta chain) were significantly up-regulated, suggesting that the shrimp diet enhances cellular immunity by promoting cytoskeletal remodeling and phagocytosis efficiency. In contrast, Treatment B mainly showed enrichment in lysosome and amino sugar metabolism pathways.