Biochemical and molecular responses of Babylonia areolata to cadmium stress

The ivory shell (Babylonia areolata)-a key species in tropical aquaculture-faces challenges from oceanic metal pollution. In the present study, the effects of different cadmium (Cd) concentrations (0, 0.375, 0.750, and 1.500 mg/L) on antioxidant capacity, immunity, and molecular response mechanisms of B. areolata were examined over a 48 h period. The results showed that in response to high Cd concentrations, the activities of superoxide dismutase and total antioxidant capacity first increased and then decreased. Compared to the control group (0 mg/L), glutathione peroxidase activity was significantly lower at 6 h and significantly higher at 24 h. However, compared to controls, malonaldehyde and protein carbonyl contents increased significantly over time. With prolonged exposure, acid phosphatase and alkaline phosphatase activities were significantly inhibited in the high-concentration group. After 24 h of Cd exposure, transcriptome sequencing identified 126,492 unigenes, of which 8792 were predicted to encode transcription factors. Notably, 464 genes exhibited differential expression in the hepatopancreas after exposure to 0.750 mg/L Cd for 24 h; 148 genes were upregulated and 316 genes were downregulated, implicating pathways associated with metabolism and immunity. Additionally, signal transduction and immune system pathways were identified as potential key pathways in the response to Cd stress. A subset of key genes (ZC3H13, CYP20A, KRAB, UAP56, PhyH, Slc6a5_9, and Ank) underwent qRT-PCR validation and showed consistency with the RNA-Seq results. This comprehensive analysis elucidates the intricate response of B. areolata to Cd stress and emphasizes the importance of understanding such stress responses for effective aquaculture management.