毒死蜱胁迫下WSSV对凡纳滨对虾的致病性

Studies of the pathogenicity of WSSV to the cultured shrimp Litopenaeus vannamei under chlorpyrifos stress

为了评价养殖水环境中毒死蜱对凡纳滨对虾生存的危害性,开展了毒死蜱胁迫下白斑综合征病毒(WSSV)对凡纳滨对虾致死实验,分析了毒死蜱胁迫下凡纳滨对虾鳃组织WSSV含量和肌肉组织乙酰胆碱酯酶活性变化。通过急性毒性实验测定了毒死蜱对凡纳滨对虾的半致死浓度(LC50),随着暴露时间的延长,LC50值显著下降,存在着浓度-反应的正向关系,96 hLC50为0.758μg/L(0.521～0.987μg/L)。在此基础上,确定了毒死蜱胁迫实验浓度为0.2μg/L,此浓度下药浴4 d后对凡纳滨对虾注射WSSV,结果显示:毒死蜱胁迫下注射WSSV组的对虾死亡率(83.33%±4.7%)极显著高于乙醇-WSSV组(40.00%±0.9%);对虾鳃组织WSSV荧光定量PCR检测结果显示:感染72 h后,毒死蜱-WSSV组WSSV含量约是乙醇-WSSV组的4倍;感染96 h后,毒死蜱-WSSV组WSSV含量显著增加,约是72 h毒死蜱-WSSV组的4.9倍,是96 h乙醇-WSSV组的5.9倍。毒死蜱胁迫下,对虾肌肉组织乙酰胆碱酯酶(AchE)活性低于对照组20%左右。由此可见,毒死蜱胁迫下,WSSV增殖速率加快,导致对虾死亡率升高。

In order to evaluate the hazard of chlorpyrifos to the cultured shrimp Litopenaeus vannamei, the lethal effect of the shrimp infected with white spot syndrome virus（WSSV）under the chlorpyrifos stress was tested,while the quantity of WSSV in the gill tissue and acetylcholinesterase acticity in the muscle tissue were analyzed. The 96 h median lethal concentration （ LC50 ） of chlorpyrifos to the shrimp was determined. The results showed that the 96 h LCs0 is 0. 758 μg/L （0. 521 - 0. 987 μg/L）, and as time prolonged, the values of LCs0 significantly declined, which showed a positive concentration-response relationship. On this basis,the stress concentration of chlorpyrifos of 0.2 μg/L was determined. After the shrimp were exposed to 0.2 μg/L chlorpyrifos for 4 days,they were infected with WSSV by injection. It showed that the cumulate mortality of chlorpyrifos-WSSV treatment （83.33 % ± 4.70 ） was significantly higher than that of ethanol- WSSV group （40.00% ± 0. 9% ）. Meanwhile, the amount of WSSV was also determined by Real-time Relative PCR at 48,72 and 96 h post-injection. WSSV quantity of chlorpyrifos-WSSV treatment was about 4 times that of ethanol-WSSV control at 72 h. WSSV quantity of chlorpyrifos-WSSV treatment was significantly increased at 96 h,which was 4.9 times that of chlorpyrifos-WSSV treatment at 72 h, and 5.9 times that of ethanol-WSSV treatment at 96 h. The acetylcholinesterase （AchE） activity in shrimp muscle tissue under chlorpyrifos stress was 20% lower than that in control group. This showed that the proliferation rate of WSSV in shrimp increased rapidly under chlorpyrifos stress, which raised the mortality rate of the shrimp.