Effect Of Guava Leaf Water-extract On The Immune Function And Anti MCRV Of Scylla Paramamosain

Scylla paramamosain is an important culture species in coastal areas of China,and the total production of culture is increasing year by year with the continuous development of the carb culture industry.But crab virus disease has become more and more frequent,also caused great economic losses to the crab industry.Guava leaf-extract has a variety of hypoglycemic,antiseptic,antiviral and antioxidant activities of bioactive components.Methods with different concentrations of GLWE dipping the crab,to observe the effect of GLWE on the survival rate,immune function and anti MCRV,and through the method of transcriptomics to explore the molecular biological mechanism on immune function and disease resistance of crab for further development of a new crab immune enhancer or water disinfectant.The study of the pre experiment to determine the salinity in the crab formal test was salinity of 10,density of 10-15/m²（test cylinder bottom area of 0.502 m²）and ammonia concentration in aquaculture water should not be higher than 0.63mg·L^-1.The research was invetigated the effect of different concentrations of Guava leaf water-extract（GLWE）on survival rate of Scylla paramamosain carrying virus and its influence on alkaline phosphatase（AKP）,acid phosphatase（ACP）,lysozyme（LZM）,superoxide dismutase（SOD）,catalase（CAT）,phenol oxidase（PO）,inducible nitric oxide synthase（iNOS）and total nitric oxide synthase（TNOS）.The results showed that the survival rate of crab is increased at first and then decreased with the increase of concentration of GLWE,which is significantly different with C0 group after 15 days（P<0.05）.Among them,the survival rate of C40 group is the highest,55.56%,but the survival rate of C0 group is the lowest,22.22%.The activities of AKP,CAT,PO and iNOS in the C80group are significantly higher than those in the C0 group at 12 h（P<0.05）.The activities of SOD,LZM in the C20&C40 group and ACP,CAT,PO in the C40 group are all significantly higher than those in the C0 group at 24 h（P<0.05）.The activities of CAT in the C10&C20 group and TNOS,iNOS in the C40&C80 group are all significantly higher than those in the C0group at 48 h（P<0.05）.The activities of AKP in all treatment groups are significantly higher than those in the C0 group,but the ACP and CAT of the C40&C80 group are significantly lower than those in the C0 group at 72 h（P<0.05）.Under this condition,10-40 mg·L^-11 GLWE significantly promoted the increase of Scylla paramamosain serum AKP,ACP,SOD,CAT,PO,NOS,LZM activity in 48 h,and the optimal effect of GLWE20-40 mg·L^-1.After dipping the same concentration of GLWE on natural and artificial infection of mud crab reovirus（MCRV）of the crab,quantitative validation of the virus of each group crab hepatopancreas at the same time.The results showed that the MCRV of natural infection group proliferated at 12 h,and the copy number of C0 and C10 group increased continuously and reached a peak at 24 h,and the copy number exceeded 1×10⁷ copies/ng RNA.The number of virus copies in C20 and C40 groups reached a peak at12 h,and then began to decline rapidly to 48 h.The copy number of C20and C40 group was always lower than that of C0 group.The number of virus copies in the C80 group is in the C0 group level except that 24 h,to72 h,the order of the copy number is C10>C80>C0>C20>C40 in turn.The change trend of MCRV in artificial infection group was similar within 24 h,and all of them proliferated rapidly at 6 h.After 12 h,it reached a small peak and then decreased to 24 h,which returned to its original level.After that,the number of virus copies in the C0 group increased rapidly and reached the highest value at 72 h and the copy number reached 1×10⁶ copies/ng RNA.The copy number of C80 group increased again after 24 h and reached the highest level at 72 h,but the copy number of virus in C20 and C40 group changed more smoothly.To 72h,the copy number of virus was ranked as C0>C80>C20>C40.It is indicated that GLWE has certain inhibitory effect on the proliferation of MCRV under natural or artificial infection,and this inhibition effect has certain concentration difference.Among them,the GLWE effect of 20-40mg·L^-11 is the best.Finally,by 40 mg·L^-11 GLWE bath S.paramamosain,successfully constructed crab liver pancreas cDNA Library and find some differentially expressed genes and pathways related merisis,immune defense and responsion.Selection of CAT,SOD,LZM,P50 and FADS6genes for quantitative verification,The results showed that the expressions of CAT,SOD,LZM,I kappa B and FADS6 genes were upregulated,which were 2.18,3.14,5.13,2.66 and 2.65 times of the control group,respectively.But,the expression level of P50 gene was lower than that.This shows that GLWE is suitable as a main component of crab immune enhancing agent or a disinfectant for the further research.