Effects of nitrogen-controlled atmospheres at different concentrations on the physiological and biochemical responses of Lasioderma serricorne (Fabricius) (Coleoptera: Ptinidae) larvae

To determine the physiological and biochemical responses of Lasioderma serricorne (Fabricius) (Coleoptera: Ptinidae) larvae to nitrogen-controlled atmospheres at different concentrations, L. serricorne larvae were exposed to nitrogen-controlled atmospheres containing 78% nitrogen (ambient air, control), 90% nitrogen, 95% nitrogen, or 98% nitrogen for 2, 4, 6, or 8 d at 29 ± 1 °C and 65 ± 5% relative humidity, respectively. Catalase (CAT) activity, superoxide dismutase (SOD) activity, soluble protein (SP) content, and ether extract (EE; crude fat) content were subsequently determined. CAT and SOD activities varied among nitrogen concentrations after shorter exposure durations, but generally decreased with prolonged exposure. SP content exhibited a concentration- and duration-dependent response, whereas EE content generally decreased with increased nitrogen concentration and exposure duration. CAT activity was significantly reduced after exposure to 90% nitrogen for 8 d and 98% nitrogen for 4, 6, and 8 d, whereas SOD activity was significantly reduced under 90%, 95%, and 98% nitrogen after 8 d of exposure. All L. serricorne larvae died after exposure to 98% nitrogen for 8 d; CAT and SOD activities, SP and EE contents were not detected using the corresponding assay methods. These findings characterize the antioxidant and energy-metabolic responses of L. serricorne larvae to nitrogen-controlled atmospheres and provide physiological evidence for the application of nitrogen-controlled atmospheres in stored-product pest management.