Effects of selenium on the growth and immune gene functions of red swamp crayfish (Procambarus clakii)

Selenium is a widely used essential micronutrients in aquaculture, but its excessive effects on crayfish growth parameters and immune system are still unclear. This study was aimed to investigate the effects of selenium concentration in the soil, muscle, fatty acid profile, and gene expression of crayfish cultured in rice co-culture (CRC) model fed with commercial feed for 3 months in three locations of Guangxi Province. For this purpose, the soil samples of the three locations were collected and analyzed with the muscles of crayfish harvested were analyzed for selenium concentration. The Agilent Technology (7800 ICP-MS) was used to analyze selenium levels in soil, as well as muscle and fatty acid profiles. Additionally, gene expression profiling was conducted using qPCR, along with transcriptome analysis. On the one hand, we observed increased selenium concentrations in soil and muscle samples with significant differences (P < 0.05). Significant increases in AKP and T-AOC were observed in Guiping (P < 0.05), with Gangnan exhibiting the lowest T-AOC levels and Qintang the lowest AKP levels. On the other hand, the boosted antioxidant defenses (SOD and CAT) and reduced lipid peroxidation (MDA) in Gangnan might indicate a more favorable oxidative environment in this area. The results demonstrated that selenium exerted a targeted effect on specific growth-related genes while overall growth remained largely unaffected. Furthermore, it was observed that selenium had a positive effect on the expression of immune-related genes in crayfish, which may have resulted in an enhanced immune response. In conclusion, the notable elevation in selenium levels in the soil, coupled with pronounced discrepancies(P < 0.05), may exert considerable influence on the muscle and fatty acid profile of crayfish. Furthermore, this increase in selenium levels may also have implications for the growth and immune functions of crayfish.