Cultivation and Effects of Environmental Factors on Carrying WSSV Virus of Litopenaeus Vannamei
|School||Guangdong Ocean University|
|Keywords||Carrying WSSV virus of Litopenaeus vannamei temperature ammonia nitrogen nitrite nitrogen isease resistance immune parameters|
1. The paper designed the end of sand filter culture system to culture the vannamei, which with the function of biological isolation and self-purification capacity. The farmin- g system tested the water quantity regularly, including the number of Vibrio and heter- otrophic bacteria, ammonium, nitrite nitrogen, to reflect the stability of the farming syst- em. The water quality processed after the sand filtration system, the Vibrio, heterotroph- ic bacteria, ammonia and nitrite content of nitrogen maintained at a stable level （the rang- e of ammonium nitrogen 0.385-0.523mg/L; nitrite nitrogen in range 0.138-0.267mg/L）.2. In this experiment, we soak infected Litopenaeus vannamei with different concentrations of WSSV virus crude extract, at the same time, determined the death and the virusing Situation of Litopenaeus vannamei. The results showed that: with increasing the concentrations of WSSV virus crude extract, the death rate of Litopenaeus vannamei has increased. The death rate of the experimental group with WSSV virus crude extract, 10-1 times, 10-2 times, 10-3 times was 41.11 %、30 %、14.44 % and 2.22 %, at the same time, detected the incidence of Litopenaeus vannamei by nest PCR. The results showed that: The experimental group with 10-3 times was negative by a step PCR detecting, at the same time, other experimental group were positive. But the experimental group with 10-3 times was positive.3. In our culture model, under different temperature gradients, by detecting the mortality blood cell quantity, PO activity, SOD activity of Carrying WSSV virus of Litopenaeus vannamei, to research the reaction to temperature stress. With the temperature increasing, the mortality rate of it decreased. At 0-4 day, total haemocyte count and PO activity were descending; they were descending 7 day after. With the temperature increasing, SOD activity was increased firstly and then decreased, after 7 day, it is stable. The results indicated that to improve water temperature appropriately, the survival of Carrying WSSV virus of Litopenaeus vannamei was increased. The experimental group （30℃） in the immunological parameters was significantly higher than other groups （P﹤0.05）.4. In our culture model, under ammonia gradients, by detecting the mortality blood cell quantity, PO activity, SOD activity of Carrying WSSV virus of Litopenaeus vannamei, to research the reaction to ammonia stress. From 1 day to 7 day, the PO of low concentration group were upward trend, and significant changes （P﹤0.05）. The mmunological parameters of the high concentrations groups were on the contrary. The PO, CAT and total haemocyte count in all the test groups were less than the control group. Under high concentrations of ammonia for a long time,the disease resistance was down, With the increase of ammonia concentration, the immunological parameters of Litopenaeus vannamei was all down. The results indicated that ammonia nitrogen could reduce the immune responses of Carrying WSSV virus of Litopenaeus vannamei. To reduce ammonia concentration in water, the survival rate of Carriers can increase.5. In our culture model, under nitrite gradients, by detecting the mortality blood cell quantity, PO activity, SOD activity of Carrying WSSV virus of Litopenaeus vannamei, to research the reaction to nitrite stress. With the nitrite concentration increasing, the mortality of carriers was on upward trend. The number of deaths in each experimental group was stable 7 days after. Under the Low nitrite concentration conditions （0.05, 0.10 mg/L）, the total haemocyte count of carriers was not significant change, under the high nitrite concentration conditions （0.50, 0.70 mg/L）, the result was contrast 7 day, the PO activity of the serum was increased first and decreased then. The PO activity of all experimental groups were lower than the control group after 10 days, the PO activity of high concentrations groups were significantly lower than the low concentration group. The results indicated that the nitrite could reduce the immune responses of healthy Litopenaeus vannamei. To reduce the nitrite concentration in water, the survival rate of Carriers can be increasing; the disease resistance of carriers was increased.