| Portunus trituberculatus was an important aquaculture species. However, due to a series of questionsto make the disease worsening, especially the muscle-emulsified disease caused by the Vibrio alginolyticus,seriously restricted the healthy development of aquaculture industry of P. Trituberculatus. For this reason,our lab have started to cultivated a new strain of resistance V.alginolyticus science2005and obtained thenew breed of anti-V.alginolyticus which was named “Keyong NO.1”. In this paper, on the one hand,according to measure the traits to study the growth characteristics of “Keyong NO.1”, which can offer theretical refence for high yield cultivation and selection breeding assisted by morphological traits. On theother hand, by measuring immune-related indicators to study its immunological properties, which providethe theoretical evidence for resistance breeding.The growth characteristics of “Keyong NO.1”What the traits of “Keyong No.1” measured at six months were aimed to study the growth regulationof it, including body weight (BW), body length (BL), full carapace width (FCW), carapace width (CW),body height (BH), meropodit length of the claw (MLC), fixed finger length of claw (FFLC) and meropoditlength of the first peraeopod (MLFP).The correlation coefficients and path coefficients were calculated by correlation analysis and pathanalysis, then morphometric attributes of every month age that affect the body weight were determined.The results showed that FCW at month age of1and BL at month age of3,4revealed maximum directinfluence on body weight. CW was an common important attribute that affect the weight of every monthage except the month age of1. BH at month age of1and BL at month age of5,6showed the mostimportant indirect influence on body weight. Then the best multiple linear regression equation wereestablished to estimate the body weight by morphometric traits in every month.The traits at different age were analyzed by using principle component analysis and comprehensivedescribed with the length factor, width factor, hight factor and body weight factor. The results showed thatthe traits were only the first principle component at1,2and3month age, the width factor, hight factor andwidth factor was the first principal component of1,2and3month age. At4,5and6month age, the firstprincipal component was body weight factor and its second principal component was length factor.Three growth models, Logistic, Gompertz and Von Bertalanffy, were used as the candidates forstudying the growth regular pattern of traits. Results showed that Logistic model is the best model todescribe the growth of body weight, with squared multiple correlation coefficient R2reaching0.999.However, the other traits were best confirmed to Von Bertalanffy model, the squared multiple correlationcoefficient R2were ranged0.99from0.994. In addition, the fasten growth intervals and growth inflectionpoints of body weight were2.14~3.91months and3.02months, the start-point of fasten growth intervals ofthe other traits were0months and the end-point were2.05~2.35months. The growth inflection points wereabout1month. Moreover, the growth rate, the growth acceleration, the relative growth rate and the absolutegrowth rate were different among varying traits. The immunological properties of “Keyong NO.1”The wild group and “Keyong NO.1” with the body weight of about20g were infected in200μLconcentration of1.14×107cfu/mL of V.alginolyticus. Results showed the time of large number of deaths ofwild group and new strains were7hours and14hours. The survival rate of wild group was15%after48hours of infection,“Keyong NO.1” was41.7%. All above results insinuated the new strain had a strongercapacity of anti-V.alginolyticus infection than wild group.The non-specific immune parameters in hemolymph of wild group and new strain was evaluated bysome indicators, including the number of blood cells, a large proportion of granulosa cells, phagocyticactivity, serum protein content and the enzymes activity of alkaline phosphatase, acid phosphatase,superoxide dismutase, peroxidase, hydrogenperoxidase, inducible NOS. The results showed theseindicators emerged changes in varying degrees after infection. what’s more, the tendency of these indicatorsalso suggested it could reflect the extent of anti-V.alginolyticus of P. trituberculatus. According to juxtaposethe difference of indexs between wild group and new strain, it was a fact that the resistance to disease of“Keyong NO.1” was significantly higher than the wild group.The relative expression of immune-related genes in hepatopancreas of “Keyong NO.1” and the wildgroup were measured by real-time quantitative PCR. The immune-related genes includedanti-lipopolysaccharide factor, crustin, superoxide dismutase, lysozyme and hemocyanin. The resultsshowed that the immune-related genes manifested some certain tendency after infection. However, theexpression levels and the time of reaching the peak were different in different variations of the gene, it wasalso different about the variation tendency. The above-mentioned indicated these genes may participate inthe process of clearing V.alginolyticus and protecting the body’s immune defense. In a short, what theresistance to disease of new strain was significantly higher than the wild group might relate the differencesof expression and trends. |
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