| Summary: | 碩士 === 國立嘉義大學 === 生物資源學系研究所 === 103 === Farming oyster is an important industry of aquaculture in Taiwan. Some farmers complained there were mass mortalities recently. To study the causes of mass mortalities , a survey of diseases was carried out. The sampling works were complemented in farming areas of Changhua, Yunlin, Chiayi and Tainan. Those are major oyster farming areas in Taiwan. The results of the survey showed all the sampled oysters without being infected, but all had the mucous cells in some of their tissue. Then the variations of density of the mucous cells in the farmed oyster relating to the environmental factors and size of oyster were studied. The highest average density of the mucous cells was found in the epithelial tissues of gills, that of the mantles followed, the third was that of digest ducts. It might be that gills had large area immersing in water resulting in having more stress from environment, and had spent much energy to filter water that weakened the immunity. The oyster farmed on the intertidal zones had less dense mucous cells than those in the lagoons and deep waters. The production of mucous cells might be inhibited by torpor of the oyster during the low tidal periods. Fast growth of the oyster in deep waters might share the energy that lessened the immunity. Salinity, dissolved oxygen and pH of surveyed sea waters had no significant relationship with the densities of the mucous cells. In the warm season, the densities of mucous cells were higher than that in cool season, high temperature could enhance production of mucous cells. The small oyster sedentary on the surface of live large oyster had higher densities of mucous cell than those on the clutches of used oyster shells. It showed that competition of food might weaken the small oyster. The results of the survey showed that the oyster might have been stressed by unadequate farmed environments, and diseased might happy if environments become worse.
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