The physiological changes and the impact of rapid cold hardening on the survival ability of Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) under cold stress

Dastarcus helophoroides (Fairmaire) serves as an ideal biological control agent for forest beetles. However, its survival ability at low temperatures is a critical factor for its use in colder regions. This study investigates the survival ability, supercooling point (SCP), impact of rapid cold hardening (RCH) and physiological changes of D. helophoroides under cold stress. SCPs of adults that underwent RCH were lower than those of adults cultured at room temperature, with SCPs of −25.1°C and −16.9°C, respectively. As the cold stress temperature decreased in the test, the survival ability of D. helophoroides adults also diminished, reaching the lowest survival rates at −20°C across all observation time points in the test. However, adults induced by RCH exhibited higher survival rates than those cultured at room temperature, suggesting that RCH enhances the cold resistance of D. helophoroides. The activities of superoxide dismutase (SOD) and catalase (CAT) in the adults increased as the stress temperature decreased. With prolonged cold stress, the activity of lactate dehydrogenase (LDH) initially decreased and then increased. Both fat and water content decreased with the lowering of stress temperature. These results provide insights into the cold resistance strategies of D. helophoroides.