Metabolic and Immune Response of Juvenile <i>Babylonia areolate</i> to Hypoxia Stress

As an important aquaculture species, the marine snail Babylonia areolate is frequently subjected to fluctuation in dissolved oxygen concentration during farming and transportation processes. In the present study, we measured the oxygen consumption rate, ammonia excretion rate, metabolic enzyme activities, immune enzyme activities, as well as changes in gene expression of these enzymes under long-term stress (144 hours) on B. areolate at two hypoxia levels (2.0 and 0.5 mg O2/L). The findings indicated that the mortality rate of juvenile B. areolate was higher in the 0.5 mg O2/L group compared to the 2 mg O2/L group. During the hypoxic stress period, both oxygen consumption and ammonia excretion rates were observed to be lower in juvenile B. areolate than those in the control group. The group exposed to 0.5 mg O2/L exhibited lower oxygen consumption and ammonia excretion rates compared to the group exposed to 2 mg O2/L at most measurement time points. As stress duration prolonged, juvenile B. areolate demonstrated significantly elevated activities of PK and ACP, alongside reduced activities of LDH, ACP, and SOD. The expression levels of PK and LDH genes in juvenile B. areolate were significantly reduced during the early stages of hypoxic stress; however, a significant increase was observed in the later stages. The expression levels of ACP and AKP genes were significantly downregulated, while juvenile B. areolate exhibited elevated SOD gene expression levels under 0.5 mg O2/L. The results indicated that B. areolate may respond to hypoxic stress by reducing its metabolic rate and modulating the expression of metabolism-related enzymes. Furthermore, hypoxic stress was found to significantly impact the antioxidant capacity and immune function of B. areolate. Notably, the mortality rate of B. areolate can be substantially decreased by ensuring that transportation time does not exceed 48 hours.