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 a -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.