氨氮胁迫下白斑综合征病毒对凡纳滨对虾的致病性

为了评价养殖水环境中氨氮(NH_4-N)对凡纳滨对虾(Litopenaeus vannamei)的危害性,开展了NH_4-N胁迫对凡纳滨对虾感染白斑综合征病毒(WSSV)后的死亡率、WSSV增殖速率和对虾主要免疫相关酶活性影响的实验。在NH_4-N胁迫质量浓度为15.6 mg·L-1,分别注射2×105和2×106个WSSV粒子,结果显示,NH_4-N胁迫下注射2×105个WSSV粒子的凡纳滨对虾第144小时死亡率达到53.3%,显著高于无胁迫组(40.0%)。对虾鳃组织WSSV荧光定量PCR检测结果显示,NH_4-N胁迫下凡纳滨对虾鳃组织内WSSV的增殖加快。此外,免疫相关酶活性结果显示,NH_4-N浓度突变会促使对虾血清中酚氧化酶(PO)、酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活性短暂升高后持续降低。由此可见,NH_4-N胁迫会加快WSSV在患病凡纳滨对虾体内的增殖,导致更高死亡率,这可能是因为胁迫造成了对虾免疫相关酶活性降低和抗病原感染能力下降。

Study on pathogenicity of WSSV to Pacific white shrimp (Litopenaeus vannamei) under ammonia stress

To evaluate the harmfulness of ammonia on Pacific white shrimp (Litopenaeus vannamei),we investigated the effects of ammonia (NH4-N) on mortality of the shrimps infected with WSSV (white spot syndrome virus),WSSV proliferation and activity of immune-related enzymes in serum.The shrimps were infected intramuscularly with 2×105 and 2×106 viral particles under the stress of 15.6 mg·L-1 NH4-N.The results show that the shrimps with 2×105 WSSV got mortality of 53.3% at 144th hour,which was significantly higher than that of the control group (stress-free).Meanwhile,the real-time relative PCR shows that ammonia stress accelerated WSSV proliferation in shrimp gills.In addition,it is showed that,under ammonia stress,the activities of immunity-related enzymes such as phenoloxidase (PO),acid phosphatase (ACP) and alkaline phosphatase (AKP) in shrimp serum continued to decrease after a brief rise.The results indicate that ammonia stress accelerates WSSV proliferation in shrimps and causes higher mortality,which is related to the decrease of activities of immune-related enzymes under ammonia stress.