Molting, tissue calcium‑phosphorus deposition and immunity of juvenile Chinese mitten crab (Eriocheir sinensis) fed different levels of calcium and vitamin D₃

Molting activity and innate immunity play a pivotal role in the development and growth of crustaceans and are related to mortality and body abnormality. To evaluate the synergistic effect of vitamin D₃ (vit-D₃) and Ca in molting and immunity in Chinese mitten crab (Eriocheir sinensis), the crabs (3.20 ± 0.01 g) were fed six diets formulated with two Ca levels (0% and 1.5%, abbreviated D and N) and three vit-D₃ levels (0, 9,000 and 27,000 IU/kg, abbreviated LVD, MVD and HVD) level for 56 days. Crabs fed 1.5% Ca and 9,000 IU/kg vit-D₃ (N + MVD) had the highest growth performance, hematic-1,25-dihydroxy vit-D₃, hematic‑calcium, hepatic‑phosphorus and antioxidant capacity among all groups. On the contrary, crabs fed diets without Ca reduced growth performance, tissue calcium‑phosphorus deposition, antioxidant capacity, and the expression of molting-related and immune-related genes. Compared to crab fed N + HVD (1.5% Ca + 27,000 IU/kg vit-D₃), those fed D + HVD (0% Ca +27,000 IU/kg vit-D₃) had significantly low growth performance and the gene expressions of molting and antibacterial immunity. This study demonstrates that adequate dietary calcium and vit-D₃ can enhance growth, molting activity, antioxidant capacity and innate immunity in E. sinensis. Moreover, it provides an in-depth understanding of the molecular mechanism of molting activity and antibacterial immunity in Chinese mitten crab