The heat-resistant capability analysis of two populations of Sinonovacula constricta under thermal stress

Extreme summer weather driven by global warming is a primary environmental factor leading to the high mortality rate of the razor clam (Sinonovacula constricta). In order to screen high resistance of the razor clam facing high temperature, a comparative study of two populations (Shenzhe population, SZ; Zhejiang population, ZJ) under thermal stress was conducted. These two populations were cultured in the same sea area, but with different parental origins. The survival rate, antioxidant enzyme activity and tissue damage were determined in razor clam under thermal stress. The results indicated that upper incipient lethal temperature (UILT) of SZ was significantly higher than that of ZJ by 0.66 °C. Under identical initial water temperature, the critical and lethal thermal maximum (CTM<M) of SZ were also significantly higher than those of ZJ. The oxidation indicators of razor clams from the two populations showed different responses to thermal stress, including superoxide dismutase (SOD), catalase (CAT), reactive oxygen species (ROS), and glutathione peroxidase (GPX). Additionally, the two populations exhibited disparate levels of tissue damage under thermal stress conditions. Comparisons revealed that SZ exhibited higher antioxidant enzyme activity, more efficient ROS removal, and less tissue damage compared to ZJ under the same conditions. In summary, the Shenzhe population exhibits better tolerance to high temperatures, making it a potential candidate for breeding new heat-resistant strains of razor clam.