Heat hardening enhances the energy metabolism activity and oxidative defense ability of Manila clam Ruditapes philippinarum under different thermal stress

Abstract

Heat-hardening treatment can improve the thermal tolerance of aquatic organisms, likely due to enhanced antioxidant capacity and energy metabolism. In this study, the Heat-hardened Manila clam exhibited an increase in survival rate ranging from 15.5% to 80% compared to Non-hardened Manila clam under acute heat stress. Under chronic heat stress, following sub-lethal heat shock treatment, the activities of antioxidant enzymes-Catalase (CAT), Glutathione peroxidase (GSH-PX), Superoxide dismutase (SOD) in Heat-hardened Manila clam was significantly elevated in comparison to the control group (P < 0.05). Compared with the non-hardened Manila clam, the activity of energy metabolism enzymes - Na+/K+-ATPase (NKA), Ca2+/Mg2+-ATPase (CMA) of heat-hardened Manila clam decreased after the first sublethal heat shock treatment, and increased during recovery treatment, and the total ATPase activity significantly increased. Within 7 days of chronic heat stress, the activities of CAT and SOD in the Heat-hardened group higher than that in the non-hardened group. The balance between antioxidant ability and energy metabolism may be critical for the enhanced thermal tolerance observed in the Heat-hardened Manila clam. These findings indicated that Heat-hardening treatment is likely to enhance the resistance of Manila clam to high temperature in the natural environment. Such insights could be advantageous in aquaculture to protect Manila clam from the detrimental effects of heat stress.