亚硝酸盐氮对凡纳滨对虾毒性和抗病相关因子影响

THE TOXICITY OF NO_2-N ON LITOPENAEUS VANNAMEI AND EFFECTS OF NO_2-N ON FACTORS RELATING TO THE ANTI-DISEASE ABILITY

用常规生物毒性实验方法,在不同盐度下进行亚硝酸盐氮对凡纳滨对虾的急性毒性实验;并加亚硝酸盐氮于凡纳滨对虾的养殖环境中,检测与抗病力相关因子的变化。研究亚硝酸盐氮对凡纳滨对虾的毒性和抗病力相关因子的影响。结果表明:盐度对亚硝酸盐氮的毒性有较大影响。盐度为31时,24hLC50、48hLC50、72hLC50和96hLC50分别为314.9mg/L1、75.3mg/L1、00.2mg/L和89.0mg/L;盐度为17时,分别为132.3mg/L、65.6mg/L、51.3mg/L和39.5mg/L。盐度31实验组的亚硝酸盐氮半致死浓度均显著(P<0.05)高于盐度17实验组。在低盐度条件下亚硝酸盐氮的毒性较强。亚硝酸盐氮对凡纳滨对虾抗病力相关因子有显著的影响。亚硝酸盐氮浓度为4.0mg/L和8.0mg/L时,其血细胞数、超氧化物歧化酶(SOD)活力、酚氧化酶(PO)活力、抗菌活力(Ua)、溶菌活力(UL)和血清蛋白含量均显著(P<0.05)低于对照组;不吸污组抗病力相关因子活性均显著(P<0.05)低于吸污组。低浓度的亚硝酸盐氮可降低凡纳滨对虾抗病能力,亚硝酸盐氮浓度越高,其抗病能力越弱。

NO2-N is one of the main contaminations and a great stress factor in the intensive prawn culture system. Therefore it is very important to study the toxicity of NO2-N on Litopenaeus vannamei and effects of NO2-N on factors relating to the anti-disease ability for the health culture of L. vannamei. Acute toxicity test of NO2-N to L. vannamei was done by the usual method of biological toxicity test at different salinity. According to the result of acute toxicity test, NO2-N was introduced into the culture system of L. vannamei at tow levels（4mg/L,8mg/L）. Those without introducing NO2-N were used as controls. The water in the culture system was changed with proportion of 100% every day. NaNO2 was introduced into the same system with the same concentration of NO2-N. Without renewing water, two experiment group were set. The filth of group 1 was cleared once every 4 days, while group 2 was not. The blood serum of prawn was drawn out on day 18 and the changes of the hemocyte number, the content of blood serum protein and the activity of phenoloxidase, superoxide dismutase, antibacterial enzyme, lysozyme of L. vannamei were tested. The result shows that the salinity had remarkable effect on the toxicity of NO2-N. When the salinity was 31 in the culture system, the 24hLC50 ,48hLC50, 72hLC50, 96hLC50 was 314.9mg/L, 175.3mg/L, 100.2mg/L and 89.0mg/L, respectively; when the salinity was 17, the corresponding concentration was 132.3mg/L, 65.6mg/L,51.3mg/L and 39.5mg/L, respectively. All LCs0 of the experiment group with salinity of 31 was significantly higher（ P〈0.05）than that of the experiment group with 17. The toxicity of NO2-N was greater under the condition of lower salinity. NO2-N showed obvious effect on the anti- disease ability of L. vannamei. Under water-renew condition, and the NO2-N was 4mg/L and 8mg/L in the culture system, the hemoeyte number, the content of blood serum protein and the activity of phenoloxidase, superoxide dismutase, antibacterial enzyme, lysozyme of L. vannamei were deelined 66.3%, 6.5%, 21.9%, 18.9%, 24.8%, 48.9% and 68.3%, 11.6%, 43.9%, 23.9% ,59.6% ,56.9%, respectively in contrast to the control group. The activity of factors relating to the anti-disease ability was signifieantly lower（ P〈0.05）than that of the control group. Under the experiment condition without renewing water, the activity＇of factors that relate to the anti-disease ability in group 2 was significantly lower（ P〈0.05）than that in group 1. The result applies that the anti-disease ability of L. vannamei deelines in the range of lower eoneentration of NO2-N and the higher NO2-N concentration is, the weaker anti-disease ability will become.