| According to the subsistent problems in the aquaculture of sea cucumber, Apostichopus japonicus (Selenka), studies were carried on characteristics of basic biology, histology, respiratory physiology and physio-ecology, the carrying capacity was evaluated and culturing pattern was optimized. Culturing experiments were evaluated in situ experiments in the Shengsi Islands, southern China. The main results were listed as follows:1.The coelomocytes, suspended in the coelomic fluid and occurring in the coelomic epithelial layer of the sea cucumber Apostichopus japonicus (Selenka), functioned as mediators of the immune system, trephocytic cells and nutrient transport cells. Types of coelomocytes are characterized based on their morphological and ultrastructural features. Flow cytometry plus light and electron microscopic analyses were conducted in order to characterize the coelomocytes of A. japonicus. Six types of coelomocytes were identified: lymphocytes, morula cells, amoebocytes, crystal cells, fusiform cells and vibratile cells. The mean±SD coelomocyte concentration in the individuals (body length: 10 to 15 cm; weight: 100 to 150 g) was (3.79±0.65)×106 cells ml-1. Altogether four different types of haemocytes have been recognized and described by their morphological characterization: lymphocytes, amoebocytes, morula cells, crystal cells. Phagocytic activity was in relation with the elevated temperature and the exposure time. Amoebocytes showed strong clotting reaction.2.Ultrastructural characterization of haemal vessel, respiratory tree, myocyte, and coelomic epithelial cell in Apostichopus japonicus were complicated, there was close relationship between the structure and function. The reabsorption of gut during artificial induced aestivation was prominent. The gut was atrophic and showed the well adaptation to the high temperature is exited. There was positive correlation between PO2 and pH and negative correlation between PO2 and PCO2. The PO2 was slightly increased during aestivation, no significant differences were found before and during aestivation. The continuous sampling had no significantly effect on the changes of PO2, PCO2 and pH. There was negative relationship between the body weight and %Extrw , %EwO2.3.The disturbance of sea cucumber decreased the contents of organic matter, TOC, TN, Chl. a, and the total sum of bacterium in the sediment, and inhibited the anaerobic processes coupling sulfite production in sediment. The selective feeding of sea cucumber was illustrated by the higher OM content in the feces.4.The carrying capacity for the ranching of sea cucumber in offshore deep water area was evaluated according to the physiochemical characteristics, supplement of natural deposited sediment of local area and the absorption rate in different temperatures, which was about 109.40 g y-1m-2.5.The OM in near shore area was higher than that in offshore area, the partial size was more edible for the ranching of sea cucumber in near shore area. The depth for sea ranching and reef of sea cucumber were 5-12 m. The suitable ranching size for A. japonicus in deep water was with the weight exceeded 30g。6.Culture of the sea cucumber, Apostichopus japonicus, was evaluated in situ experiments in the Shengsi Islands, southern China. Three size groups of sea cucumbers were cultured in abalone cages and survival and growth were monitored semimonthly or monthly. Fermented seaweed was used as feed. The sea cucumbers in all four sites showed excellent survivorship (≥83%). Growth rates were negatively correlated with culture densities; growth rates of large juveniles at high densities were the same as growth rates of medium and small juveniles that were not stunted at high densities. Juveniles of all three sizes grew progressively except after April when temperature increased. We conclude that A. japonicus at a size of 40 g and a density of 3-5 ind layer-1 can be farmed successfully in raft culture system. |
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