| Penaeus monodon is also called grass shrimp, black tiger shrimp. It is widelydistributed in the western Pacific and most of the Indian Ocean and also one of theworld,s three major cultured shrimp species,in China the coast of Zhejiang, Fujian,Guangdong, Hainan, Guangxi and Taiwan distributed. Ammonia-N is an importantpollution factor in the aquaculture environment, has a major impact on growth, molting,osmotic regulation, immune system, excretion of shrimp. Exposed to ammonia-Nstress response and a decline in immune and detoxification function, was an importantfactor of disease，low survival rate and farming cost-effective of shrimp. So new lines ofshrimp which are a fast growth, disease resistance and stress tolerance are key to blacktiger shrimp aquaculture recovery and sustainable development.In this paper, growth traits of hybred combination and inbred combination betweendifferent geographic populations and families,resistance to ammonia were tested toprovide basis for the selective breeding of news lines in in Penaeus monodon.The halflethal concentration of ammonia-N were got to carry out ammonia-N acute toxicity for96h. Under ammonia-N level of29.9mg/L the immune parameters of Penaeusmonodon in serum, immune-related gene expression (Lysozyme, Crustin, Anti-LPSfactor/ALF) and glutamine synthetase activity (GS) and glutamine content inhepatopancreas, muscle, gill were studied. The main results were as follows:Inbred combination consisted of two groups of SS (S×S),TT (T×T) andhybrid combination including two groups of ST (S×T),TS (T×S) wereestablished based on two different geographic populations of wild Penaeus monodonthat were from Sanya (S) and Thailand (T). Five growth traits (body length, bodyweight, cephalothorax length, cephalothorax width, cephalothorax height) of six monthold offspring of four groups were measured. The five traits among four groups are ST>TS> TT> SS. Study has shown that the gene diversity was stong differentiationbetween populations from the western Pacific Ocean and the south China Sea. Itprovided the theoretical basis for heterosis between the sanya and Thailand population.Heterosis of hybrid combination in five traits was calculated at a range values(2.13-19.7%). Heterosis of body weight was the highest. It was found that heterosis ofhybrid group ST was higher than heterosis of hybred group TS in each trait.ANOVA showed that the traits of body length, body weight, cephalothorax length, cephalothoraxheight of offspring from four groups were significant difference (P <0.05) and bodylength, body weight, cephalothorax height were more significant difference (P <0.01),while the trait of cephalothorax width was no significant difference. The results ofanalysis of multiple covariance showed that the hybrid group of ST had significantdifferences in traits of length, body weight, cephalothorax length than inbred groups(SS,TT)(P<0.05).The result display that the growth can be improved by crossing withdifferent geographic populations. The study provides basis for the selective breeding ofstess-resistance lines in Penaeus monodon.Families were established based on three different geographic populations of wildPenaeus monodon that were from Africa (F),Thailand (T) and Indonesia (Y).Thosefamilies were used to compare their resistance to ammonia by acute toxicity. The resultsshowed that there were extremely significant differences(P<0.01) in the resistance toammonia among different families.Compared with other families,the resistance toammonia of F243×F381was highest, F243×F381was lowest. ANOVA showed that theresistance to ammonia of offspring from four combinations (F×F, Y×Y, Y×T, T×Y) was no significant difference (P>0.05). The resistance to ammonia ofoffspring from natural insemination was significantly higher than from artificialinsemination. The study provides basis for the selective breeding of stress-resistancelines in Penaeus monodon.The results of acute toxicity test of ammonia-N on Penaeus monodon carriying outby biological toxicity test showed that effect of toxicity has a significant positivecorrelation with the ammonia-N maintained time and concentration. In the condition ofseawater30℃, pH=8, S=34.5, the half lethal concentration of ammonia-N were2.63mg/L,39.68mg/L,31.65mg/L and29.94mg/L, lasting for24h,48h,72h and96hrespectively, and the safe concentration was2.99mg/L. In the same concentration, halflethal concentration of non-ionic ammonia were2.81mg/L,2.12mg/L,1.69mg/L,1.60mg/L respectively and the safe concentration was0.16mg/L. The effect of ammonia-Nlevel of29.9mg/L on immune parameters of Penaeus monodon showed the variationtrend of different immune parameters: including activity of phenoloxidase (PO)decreasing in the whole of study, superoxide dismutase (SOD) and peroxidase (POD)activity in serum increasing at first after ammonia-N stimulated and then decreasing,acid phosphatase (ACP) of activity increasing at first after ammonia-N stimulated, thendecreasing and increasing at last within96h. ANOVA indicated that the activities of PO,SOD, POD, ACP in seven sampling points(0h,4h,8h,12h,24h,48h,72h,96h) weresignificant difference (P <0.01), while the control groups all were no significant difference (P>0.05). Acute toxicity result, changes of different immune parameters inhigh ammonia-N stress and influence of high ammonia on the immune system obtainedin this study support a scientific basis for the healthy development of culture of Penaeusmonodon.Penaeus monodon exposed to29.94mg.L-1ammonia-N were examined forimmune-related gene expression (Lysozyme, Crustin, ALF) in hepatopancreas, muscle,gill. Lysozyme expression in hepatopancreas, muscle, gill increasing at first afterammonia-N stimulated and then decreasing, were up to maximum at12h,48h,24hrespectively, and increased by68.95%,58.64%,165.61%in those tissues respectivelycompared with the control group. Crustin expression after96h in hepatopancreasdecreased ignificantly (P <0.05). Crustin expression in all sampling points(24h,48h,72h,96h) in muscle increased ignificantly (P <0.05) compared with the controlgroup,reached to the maximum at72h and increased by514.37%. Crustin expressionsin gill were at the normal levels. ALF expressions in hepatopancreas were at thenormal levels. ALF expression in muscle increasing at first after ammonia-N stimulatedand then decreasing, were up to maximum at24h, and increased by50.92%comparedwith the control group. ALF expression in all sampling points(48h,72h,96h) in gillwere higher than the control group, after96h decreased significantly (P <0.05).Penaeus monodon exposed to0(the control),10,20,30mg.L-1ammonia-N wereexamined for glutamine synthetase activity and glutamine content in seven samplingpoints(0h,24h,48h,72h,96h) in hepatopancreas, muscle, gill. The results showed thatglutamine synthetase activity for all treatment groups in hepatopancreas, muscle insampling points (24h,48h,72h,96h) all higher than the control. ANOVA indicated thatglutamine synthetase activity in all tissues in96h were significant difference (P <0.01).Glutamine synthetase activity in all tissues had a positive correlation with theammonia-N maintained concentration. Glutamine content for all treatment groups inhepatopancreas, muscle,gill in sampling points (24h,48h,72h,96h) all higher than thecontrol.Glutamine content in hepatopancreas, muscle in96h were significant difference(P <0.05). The results indicate that ammonia-N could be transferred into glutamine inhepatopancreas, muscle, gill, then transported or stored in tissues. It may be a way ofammonia-N detoxification which decreased the mmonia-N content and reduce thetoxicity of ammonia-N. |
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