Keywords: 
• Litopenaeus vannamei /
• hypoxia-reoxygenation /
• alkaline phosphates /
• acid phosphatase /
• phenoloxidase

Abstract: Litopenaeus vannamei was treated with dissolved oxygen（ DO） at respective concentrations of 1. 5,3. 0,6. 5 mg·L^-1 to study the stress effects of hypoxia on the gill,hepatopancreas and haemolymph of L. vannamei. The results showed that L. vannamei was tissue specific in distribution of activities of alkaline phosphates（ AKP） and acid phosphatase（ ACP） and was obviously different in the AKP and ACP activities among the three tissues（ P ＜ 0. 05）. Of the threes tissues the hepatopancreas contained the highest AKP and ACP activities,while the three tissues contained very low phenoloxidase（ PO） activities without any obvious difference. Under the stress of hypoxia-reoxygenation,the three tissues showed a similar rise-and-decline change in the activities of the three immune-related enzymes which generally recovered to the normal level at 24 h of reoxygenation. When the DO was 3. 0 mg·L^-1 ,the gill contained the maximum activities of the three enzymes at 3 h. This indicated that the gill was first to respond to the hypoxic stress and can hence be used as a tissue indicator for hypoxic stress,and that 3 h was a critical time point for hypoxic stress in L. vannamei.