Dietary optimal arginine content of juvenile mud crab Scylla paramamosain and its roles in growth promotion and immune defense
摘要
Determining the appropriate dietary arginine (Arg) requirement and elucidating its roles in growth performance and immune defense are essential for the mud crab (Scylla paramamosain). In this study, we evaluated the effects of dietary Arg supplementation on crab growth and resistance to Vibrio. Feeding trials established 1.45% Arg of dry diet as optimal, enhancing growth, molting, and muscle-related gene expression, while both deficiency and excess were detrimental. Dietary Arg modulated the gut microbiota by enriching beneficial taxa (primarily Carboxylicivirga) and enhancing the network role of Rhodobacteraceae, and increased its immune-related functional potential including Fc gamma R-mediated phagocytosis and endocytosis. Transcriptomic analyses revealed that dietary Arg prompted immune functions of the gut and associated bacteria following Vibrio parahaemolyticus challenge, enriched immune-related pathways such as NOD-like receptor, Toll-like receptor, C-type lectin receptor, and Toll and Imd signaling. Moreover, it increased hepatopancreatic inducible nitric oxide synthase activity and nitric oxide levels. These findings demonstrate that the optimal dietary Arg enhances mud crab growth and immunity through synergistic host–microbiota interactions, providing valuable insights for formulating amino acid-balanced diets for mud crabs and novel perspectives on the functional mechanisms of Arg in crustaceans.