Effect of hypoxia-reoxygenation on the survival and antioxidant factors of Macrobrachium rosenbergii juvenile

Abstract:

To investigate the effects of hypoxia-reoxygenation stress on the survival and antioxidant factors of Macrobrachium rosenbergii larvae， this study subjected them to stress in water with dissolved oxygen concentrations of 1.0， 1.2， and 1.4 mg/L. The survival rates and half lethal concentrations （LC₅₀） at 4， 8， 12， 24， 48， and 72 hours after the onset of stress were measured and estimated； Subsequently， the juvenile M.rosenbergii was replaced in water with a dissolved oxygen concentration of 2.2 mg/L for 72 hours of hypoxia stress. The dissolved oxygen concentration was restored to 6.0 mg/L within 4 hours and 8.4 mg/L within 12 hours. The activity of antioxidant enzymes （SOD， CAT， GSH-PX）， phosphate hydrolases （AKP， ACP）， and malondialdehyde （MDA） content in gills， hepatopancreas， and muscle tissues were measured at 0， 4， 8， 12， 24， 48， and 72 hours of hypoxia stress， as well as at 4 and 12 hours after reoxygenation stress. The results showed that the mortality rate and LC₅₀ value of juvenile M.rosenbergii under three types of hypoxia concentration stress gradually increased with the prolongation of stress time， and the mortality rate was significantly higher at the 12th and 24th hours after hypoxia stress than that at the 4th and 8th hours （P<0.05）. Within 0-72 hours of hypoxia stress， the activities of SOD， CAT， and GSH-PX in the gills， hepatopancreas， and muscle tissues of M.rosenbergii larvae showed a trend of first increasing and then significantly decreasing （P<0.05）， and then significantly increasing again after reoxygenation stress （P<0.05）； After 72 hours of hypoxia stress followed by reoxygenation stress， the activities of AKP and ACP in the liver and pancreas were significantly higher than those in gill and muscle tissues， and the activities of AKP and ACP showed a trend of first significant increase （P<0.05） and then gradually decreasing， and then decreasing and then increasing after reoxygenation； The MDA content in the tissues of gills， hepatopancreas， and muscles showed an initial increase followed by a continuous decrease until it rebounded after reoxygenation； At 12-24 hours of hypoxia stress， significant changes were observed in the activities of SOD， CAT， and GSH-PX in gills， hepatopancreas， and muscle tissues （P<0.05）. In summary， this study preliminarily indicates that both hypoxia and hypoxia reoxygenation stress affect the survival and antioxidant capacity of M.rosenbergii larvae. It was found that the 12-24 hours after hypoxia stress are the key time points for the stress response of M.rosenbergii larvae.The research results will provide a basic theoretical reference for revealing the physiological and biochemical response mechanisms of M.rosenbergii under hypoxia-reoxygenation stress.