Effects of waterborne Cu²⁺ on the growth， development， survival， and antioxidant function of Macrobrachium rosenbergii zoea larvae

【Objective】 This study aimed to investigate effects of waterborne Cu²⁺ on the growth， development， survival， and antioxidant function of zoea larvae of Macrobrachium rosenbergii， so as to provide a theoretical reference for water quality safety management in the process of Macrobrachium rosenbergii aquaculture.【Method】 Using healthy Macrobrachium rosenbergii zoea larvae at stage I as tested subjects， the experiment set a control group （Cu²⁺≤0.001 mg/L） and six Cu²⁺ concentration gradient treatment groups （0.0025， 0.0100， 0.0500， 0.1000， 0.1500， and 0.2000 mg/L）， with the culture period of 25 d. The developmental stages of zoea larvae in each group was observed every 5 d using a microscope， and their body length and survival rate were recorded. The activities of copper-zinc superoxide dismutase （Cu/Zn-SOD）， catalase （CAT）， glutathione peroxidase （GPx）， and malondialdehyde （MDA） content were detected using kits. Total RNA was extracted， and the relative expressions of the antioxidant genes Cu/Zn-SOD， CAT， and GPx were detected.【Result】 As Cu²⁺ concentration increased， the daily body length growth rate and emergence rate of zoea larvae of Macrobrachium rosenbergii showed a trend of first increasing and then decreasing. In the 0.1000 mg/L group， the zoea larvae exhibited the highest daily body length growth rate and emergence rate， and their survival rate was higher than that in the 0.1500 mg/L and 0.2000 mg/L groups at all sampling time. Zoea larvae in the 0.0500 mg/L and 0.1000 mg/L groups underwent faster molting and metamorphosis； in the 0.1500 mg/L and 0.2000 mg/L groups， zoea larvae experienced inhibited development； in the 0.2000 mg/L group， zoea larvae could not fully metamorphose into shrimp larvae. The MDA contents in the control group， 0.0025 mg/L， 0.0100 mg/L， 0.0500 mg/L， and 0.1000 mg/L groups generally showed a trend of first increasing and then decreasing， with no significant differences among the groups treated with Cu²⁺ for the same time （P>0.05）. At the same Cu²⁺ treatment time， the relative expressions of Cu/Zn-SOD， CAT， and GPx genes generally showed a trend of first increasing and then decreasing as the Cu²⁺ concentration increased： on 5 d， 10 d， and 15 d， the relative expressions of Cu/Zn-SOD， CAT， and GPx genes in the 0.1000 mg/L group were higher than those in other groups； on 20 d and 25 d， the relative expressions of Cu/Zn-SOD， CAT， and GPx genes in the 0.1500 mg/L and 0.2000 mg/L groups were significantly lower than those in other groups （P<0.05）.【Conclusion】 The growth， development， survival， and antioxidant function of zoea larvae of Macrobrachium rosenbergii exhibit an obvious concentration-dependent effect on Cu²⁺concentration. When Cu²⁺≤0.1000 mg/L， it can induce a moderate antioxidant stress response， thus promoting the growth and development of zoea larvae of Macrobrachium rosenbergii and improving their survival rate. When Cu²⁺≥0.1500 mg/L， the domination of Cu²⁺ pro-oxidative effect of leads to a large （reactive oxygen species） ROS accumulation that exceeds the body’s clearance capacity， causing severe oxidative damage， thereby ultimately causing growth inhibition and causing developmental stagnation of zoea larvae of Macrobrachium rosenbergii.