Studies On The Toxic Mechanism Of Water-borne Cu～(2+) On Eriocheir Sinensis

In recent years, aquaculture industry of crustacean, especially shrimps and crabs, has shown rapid expansion in China, which has been developed into a major industry. However, effluent from human activities and application of Copper sulfate to control algal in crustacean ponds resulted in Copper (Cu²⁺) pollution that stunts the further growth of this aquaculture industry. The 2003 Report on State of the Fishery Eco-environment in China emphasized that Cu²⁺ is the heavy metal that exceeds most evidently the Standards of the Water Quality in the Fishery Industry (GB11607-89). In certain regions severity of Cu²⁺ contamination is still increasing, e.g. in the Hangzhou bay, piscatorial areas of Yangtse Rivers and the coast of Zhoushan. The average Cu²⁺ level of these waters is 0.07 mg/1, being 7 folds higher than that stipulated of GB 11607-89. Therefore, the Cu²⁺ toxicity on crustacean of fisheries is of primary concern. As Cu²⁺ pollution can be severely limiting factors to future crustacean culture potentially, studies on its influence on E. sinensis are of great significance in elucidating the physiological alterations of animals and establishing methods for safe aquaculture. In the present study the toxic mechanism of water-borne Cu²⁺ on E. sinensis is investigated in detail. This work is believed to have both important realistic and theoretic significances.Cu²⁺ is one of the important nutrient elements, being essential to synthesize hemocyanin in crustaceans. Cu²⁺ is required for normal function of many proteins, including most biological enzymes that are necessary for normal growth and development. However, excess Cu²⁺ is toxic and can causes a variety of adversely affects to crustaceans on biological functions from molecule level to cell level. Although many works on the toxic effects of Cu²⁺ on E. sinensis have already been reported, they almost focus on the evaluation of LC₅₀ of pollutants rather than on the mechanism of toxic effects of water-borne Cu²⁺, esp. the toxic impacts on the structure and function of X organ-sinus gland complex and the Y-organ, two most important organs for ecdysis and growth of crustaceans. So far the mechanism of Cu²⁺ on the growth of crustaceans has still not been well understood.In the present study, the effects of water-borne Cu²⁺ the Chinese mitten crab E. sinensis have been conducted by integrated morphologic, physiologic, biochemical, endocrinologic, ecotoxicologic approaches and equipments of electric microscopic, biochemical enzymes and trace element analysis. The aim of this work is to clarify the mechanism of toxic effects of Cu²⁺ on E. sinensis and it must not only be of important theoretic value on the toxic effects of heavy metal on crustaceans, but also provide useful references on the healthy aquaculture and the effective evaluation of water quality. The main results in this thesis can be summarized as follows:1 Effects of water-borne Cu²⁺ on molting, growth and survival in E. sinensisThe acute toxic effects of water borne Cu²⁺ on the molting rate, the weight gain and the survival rate in E. sinensis was conducted between I stage and 12-month-old juveniles. The 24, 48, 72 and 96 h LC₅₀s of Cu²⁺ on I stage juveniles (0.020 ± 0.01g) were 0.70, 0.43, 0.33, and 0.22 mg/l, and those on the 12-month-old animals (3.34 ± 0.26 g) were 18.20, 10.23, 9.12 and 8.51 mg/1, respectively. Results suggested that the survival rate of all I stage juvenile groups were higher than 50%, and furthermore it decreased in accordance with the increase of water borne Cu²⁺ level (from 0.00 to 0.01, 0.02, 0.03, 0.05 and 0.08 mg/l). The similar decrease tendency was also observed in the 12-month-old E. sinensis. In addition, the molting rate, weight gain and the survival rate of the 12-month-old animals decreased stably in accordance with the increase of Cu²⁺ level in the Cu²⁺ treated groups (0.01, 0.05, 0.10, 0.50, 1.00, 2.50 mg/l) groups. The survival rates in all groups studied were higher than 50%. Although the survival rate in...