Antioxidant and Microbiota Characteristics Across Different Mucosal Sites of Rice Flower Carp (Procypris merus)

Antioxidant and microbiota in different mucosal sites of fish play important roles. However, relevant research is lacking for rice flower carp (Procypris merus). This study investigated antioxidant and microbiota characteristics across different mucosal sites (gill, skin, and intestine) of this fish. Antioxidant analysis revealed the following: catalase activity followed gill > intestine > skin (p < 0.05); total superoxide dismutase activity showed intestine > gill > skin (p < 0.05); malondialdehyde level in the gill significantly exceeded the skin and intestine (p < 0.05); and, superoxide anion level ranked gill > intestine > skin (p < 0.05). The intestinal microbiota had the significantly lowest α-diversity (p < 0.05). Across different mucosal sites, LEfSe analysis revealed differentially abundant genera, and microbial functional prediction (BugBase) showed significant differences in Forms Biofilms, Potentially Pathogenic, Stress Tolerant, and Gram-Positive (p < 0.05). Correlation analysis between differentially abundant genera and antioxidant indicators revealed multiple significant positive correlations (p < 0.05) but no significant negative correlations (p > 0.05) in the gill; only two significant negative correlations (p < 0.05) and no significant positive correlations (p > 0.05) in the skin; and no significant correlations (p > 0.05) in the intestine. Collectively, these findings might contribute to the microecological regulation of rice flower carp.