Study On The Change Of Coelomic Fluid Indexes And Molecular Markers Related To Skin Ulcer Syndrome Resistance In Apostichopus Japonicus

Sea cucumber (Apostichopus japonicus) is one of Chinese traditional precious seafood species, which has the highest value due to its nutritional and supported medicinal properties among Holothuroidea. In recent years, sea cucumber aquaculture has developed rapidly along the northern coast of China and has expanded to south coast of China. Sea cucumber farming has become a vigorous industry in China. However, with rapid expansion and intensification of sea cucumber farming, many phenomena of germ degeneration have appeared such as low growth rate, weak disease resistance, high diseases frequency, low survival rate, which caused serious economic losses and became one of the limited factors in the sustainable development of this industry. Therefore, it's necessary to carry out diseases-related studies of sea cucumber. This paper presented the results of disease-resistant indexes selection from coelomic fluid indexes and molecular markers of sea cucumber, which would provide a theoretical basis for fry rearing and disease-resistant breeding of sea cucumber.Several basic indexes of sea cucumber coelomic fluid were studied such as the proportion of coelomic fluid to the total weight, the single maximum coelomic fluid extraction ratio, the security maximum coelomic fluid extraction ratio and the resume process of coelomic fluid in sea cucumber. The results showed as follows:â‘ The coelomic fluid ratio of small, middle and big sea cucumber was respectively: 26.88%,25.24% and 30.98%.â‘¡T he single maximum coelomic fluid extraction ratio was also determined as follows:3.27%(small sea cucumber)>3.18%(middle sea cucumber)>2.57%(big sea cucumber).â‘¢The securing maximum coelomic fluid extraction ratio was 1.5% in different type sea cucumber.â‘£The period for total cells, granule cells, transparent-lymphoid cells and the absorbency of coelomic fluid to recovery were 6 days in sea cucumber.Seven coelomic fluid indexes were studied in sea cucumber, which was carried on artificial infected sea cucumber by B.cereus. The results were followed respectively:â‘ I n 10th day, the absorbency and the granule cells of coelomic fluid differed significantly between disease-resistant sea cucumber and disease-susceptible sea cucumber (P<0.05).â‘¡In 5th day, the concentration of total cells and the transparent-lymphoid cells of coelomic fluid differed significantly between disease-resistant sea cucumber and disease-susceptible sea cucumber(P<0.05).â‘¢The alkaline phosphatase (AKP) activity of disease-resistant sea cucumber kept at high level during the experimental period and had significant difference with disease-susceptible sea cucumber from the 10th day (P<0.05); The acid phosphatase (ACP) activity of disease-susceptible sea cucmber were higher than that of disease-resistant sea cucumber(P<0.05), but dropped dramatically after the 5th day and were significantly lower than that of disease-resistant sea cucumber(P<0.05).â‘£There was no significant difference of superoxide dismutase(SOD) activity between the disease-resistant sea cucumber and control group sea cucumber(P>0.05), but the SOD activity differed significantly between disease-resistant sea cucumber and disease-susceptible ones from the 10th day (P<0.05).Genetic diversity analysis between disease-resistant sea cucumber and disease-susceptible sea cucumber was conducted using random amplified polymorphic DNA(RAPD) and amplified fragment length polymorphism(AFLP).Using 40 RAPD primers and 96 pairs of AFLP primers, nine molecular markers were obtained(4 RAPD markers and 5 AFLP markers) according to the distribution frequency and sequencing analysis, of which 6 markers were disease-resistant associated traits and 3 were disease-susceptible associated trait.