氨氮质量浓度对感染白斑综合症病毒的凡纳滨对虾的影响

研究了氨氮质量浓度渐变和突变对白斑综合症病毒(WSSV)在凡纳滨对虾体内增殖的影响。结果表明:在氨氮质量浓度突变组实验中,氨氮质量浓度从起始浓度0.05 mg·L-1向中浓度1.25 mg·L-1和高浓度3.0 mg·L-1突变过程中对凡纳滨对虾的累积死亡率和对虾体内病毒增殖影响显著(P0.05),先氨氮突变后感染WSSV实验中氨氮起始、中、高浓度胁迫下对虾累积死亡率分别为25.6%,34.4%和48.9%;病毒含量最大值分别为9.59×105,5.75×106,1.62×106copy·g-1。先感染WSSV后氨氮突变实验中氨氮起始、中、高浓度胁迫下对虾累积死亡率最大值分别为30%,38.9%和48.9%;病毒含量最大值分别为9.59×105,9.58×105,4.94×106copy·g-1,氨氮浓度渐变实验中各组至24 h对虾累积死亡率较低(P0.05),48 h后开始出现显著差异(P0.05)。先氨氮渐变后感染WSSV实验中氨氮起始、中、高浓度胁迫下对虾累积死亡率最大值分别为28.9%,30.0%和45.6%,病毒含量最大值分别为9.59×105,4.48×106,1.86×106copy·g-1。先感染WSSV后氨氮渐变实验中氨氮起始、中、高浓度胁迫下对虾累积死亡率分别为25.6%,33.3%和45.6%;病毒含量最大值分别为9.59×105,8.58×105,6.55×106copy·g-1。这表明对于携带WSSV的对虾,氨氮变化越大,WSSV从潜伏感染转为急性感染的可能越大,所以控制水质中氨氮含量在低浓度水平对预防WSS爆发至关重要。

Effects of Ammonia Nitrogen Concentrations on Litopenaeus vannamei Infected with White Spot Syndrome Virus

Marine shrimp Litopenaeus vannamei inoculated with WSSV （white spot syndrome virus） and cultured in graduate and acute changes of ammonia nitrogen concentrations to observe WSSV proliferation in L.vannamei.The ammonia nitrogen in the acute changes from the initial concentration 0.05 mg · L^-1 to 1.25 mg · L^-1 and 3.0 mg · L^-1 produced a significant effect （P 〈 0.05） on the mortality of L.vannamei and the virus proliferation in L.vannamei.The shrimps treated with ammonia nitrogen at an acute change of concentrations of 0.05 mg · L^-1,1.25 mg · L^-1 and 3.0 mg · L^-1 followed by inoculation of WSSV showed respective cumulative mortality rates of 25.6%,34.4% and 48.9%,respectively with the maximum virus contents of 9.59 × 10^5,5.75 × 10^6 and 1.62 × 10^6 copy · g^-1.However,the shrimps inoculated with WSSV prior to acute change of the ammonia nitrogen concentrations had the cumulative mortality rates of 30%,38.9% and 48.9%,respectively,with the maximum virus contents of 9.59 × 10^5 9.58 × 10^5 and 4.94 × 10^6 copy · g^-1 Every group in the graduate change of ammonia nitrogen had a lower mortality of the shrimps at 24 h but started to show significant difference in mortality at 48 h （P 〈 0.05）.The shrimps inoculated with WSSV after treated with graduate change of ammonia nitrogen concentrations of O.05 mg · L^-1,1.25 mg · L^-1 and 3.0 mg · L^-1 showed the cumulative mortality rates of 28.9%,30.0% and 45.6%,respectively with the largest virus contents being 9.59 × 10^5,4.48 × 10^6 and 1.86 × 10^6 copy · g^-1.The shrimps inoculated with WSSV before treated with the ammonia nitrogen at a graduate change of concentration displayed cumulative mortality rates of 25.6%,33.3% and 45.6%,respectively,with the largest virus contents being 9.59 × 10^5,8.58 × 10^5 and 6.55 × 10^6 copy · g^-1 These results showed that the WSSV carrying shrimps are likely easy to change from latent to acute infection when the ammonia nitrogen concentration is changed more rapidly in culture of the shrimps.