Effects Of Some Typical Environmental Factors On The Immune Responses And Outbreaks Of White Spot Syndrome In Penaeid Shrimp

White spot syndrome (WSS) is the most virulent among the penaeid shrimp virus that had been reported and caused serious shrimp and economic losses. Disease is the final result of a complex interaction among the shrimp, its environment and the pathogen itself. To resolve the problem of disease must research from many aspects. Studies on the environmental factors on the immune responses of penaeid shrimp and the infectivity of WSSV is one of the strategies to control the disease radically. We selected some typical environmental factors including temperature, ammonia nitrogen and microalgae and studied the effect of these environmental factors on the immune responses and outbreaks of WSS in Marsupenaeus japonicus and Fenneropenaeus chinsis from these aspects containing cumulative mortality, infection level , immune responses of shrimp (using Total Haemocyte Counts, plasma and HLS phenoloxidase, plasma alkaline phosphatase and acid phosphatase, plasma protein concentrations as evaluation parameters). The main results are as follows,1．Effects of temperature on the immune responses and outbreaks of WSS in penaeid shrimp The effects of temperature on outbreak of white spot syndrome of M. japonicus were studied through simulated experiments. The results indicated that outbreak of white spot syndrome in infected M. japonicus were relatively slow at 15℃and 33℃ and were fast at 23℃ and 28℃. The infected level were 28℃ group> 23℃ group > 33℃ group > 15℃ group. Accordingly, the experimental results showed that THC in infected M. japonicus were all lower than the control. With regard to PO activities, the value of 15℃ group was slightly lower than the control but that of 33℃ group was significantly higher than that. It was inferred that mechanisms of outbreak atlow and high temperatures could be different.2．Effects of temperature acute changes on the immune responses and outbreaks of WSS in penaeid shrimp Temperature acute changes (24-27℃/6h; 24-30℃/6h) can not arise the death of healthy M. japonicus, but accelerate outbreak of WSS and death of shrimp infected with WSSV. THC of M.japonicus decreases after infection and temperature acute changes accelerate the decreasing process. The decreasing level was correlated to the infection time and the range of temperature acute changes. In the initial stages, HLS PO increased due to stimulation and decreased in the anaphase. 3．Effects of ammonia nitrogen on immune responses of healthy and infected penaeid shrimp Ammonia nitrogen can affect THC, HLS PO activities and plasma protein concentrations of M.japnicus infected with WSSV. It can also affect THC, HLS PO activities, plasma alkaline phosphatase and acid phosphatase of healthy F. chinesis. The results indicated that ammonia nitrogen could reduce the immune responses of healthy F.chinesis and infected M. japonicus. Effective measures should be carried out to reduce the concentration of ammonia nitrogen in the shrimp pond in order to improve the immune responses and be avoid of outbreaks of disease. 4．Effect of microalgae on outbreaks of white spot syndrome in penaeid shrimp Outbreaks of WSS in F.chinesis was slowed after introducing Heterosigma akashiwa and the introduced microalgae can weaken the infections of WSSV in F. chinesis. Chlorella was incubated with virus solution or infected M.japonicus, respectively. The primary results detected by nested-PCR method indicated that Chlorella could carry WSSV.