Study On The Toxic Effects Of Heavy Metal Copper On Gillof Zebrafish(Danio Rerio)

Zebrafish(Danio rerio)is a tropical freshwater teleost fish,which has meaningful features of its small size,short reproductive cycle,transparent features and the external development of the transparent embryo and so on.As a model animal approved by the International Organization for Standardization,it has been widely used in genetics and developmental studies,tumor biology,molecular biology,drug screening,toxicology and environment monitoring and other fields.Gill is an organ which directly contact with the external environment,alsoit is more sensitive to environmental change.In addition,environmental change will lead to changes in blood indicators.Up to now,a few studies have been done on the toxic effects of copper on the peripheral blood and gill of zebrafish.This article from the blood index,morphological changes of gill,aspects of antioxidant defense system and immune toxicity to investigate the effect of copper on zebrafish,and provide a theoretical basis and reference for the further study on copper toxicity mechanism and environmental monitoring departments to develop water quality standards.Experiment ? Study on acute toxicity and safe concentration evaluation of heavy metal copper to zebrafish.The acute toxicity of heavy metal copper was studied with zebrafish as a test material by means of hydrostatic bioassay,and the median lethal concentration of zebrafish exposed to copper for 96h,and calculate the safe concentration.The results showed that the median lethal concentration of copper for zebrafish 96h is 0.431mg/L,the safe concentration is 0.043mg/L,so copper is a hypertoxicity substances.Experiment ? The normal structure observation of the gill structure of zebrafish.The ultrastructure of gill have been investigated using light and transmission electron microscope.The results showed that there were four pairs of holobranch,gill rakers seems to be prick-shaped,a comb arrangement in gill arch and gill lamellae are evenly arranged on both sides of the gill lamellae.By pillar cells,epithelial cells and capillary network,the base of lamellae and perivascular distribution of chloride cells,intracellular abundant mitochondria and excretory vesicle,including into two subtypes.The gill structure is similar with the gill structure of other teleost fish,which is closely related to its function.Experiment ? Effects of heavy metal copper on gill of zebrafish.Based on the acute toxicity test,three copper exposure groups of 0.05mg/L,0.1mg/L,0.2mg/L and one control group were established to study the effects of heavy metal copper pollution on zebrafish gills.The effects of copper exposure on the gill structure and ultrastructure of zebrafish were observed by light microscopy and transmission electron microscopy.The activities of superoxide dismutase(SOD),malondialdehyde(MDA),tumor necrosis factor-a(TNF-a),and fish interleukin-6(IL-6)and interleukin-1?(IL-1?)levels in gills were measured at 24h,48h,72h,96h exposed to copper to investigate the effects of copper exposure on antioxidant defense system and immune system.The results showed that the gill tissue of the exposed group showed swelling of epithelium,epithelial cells,glandular epithelium,mitochondrial swelling and prolonged exposure.Most of the cells showed senescence and cell death,and the way of death is different from the traditional cell death,such as apoptosis,necrosis,and so on.It belongs to an important non-apoptotic mode of cell death-oncosis.At 24h,48h,72h and 96h,the activities of SOD and the content of MDA in the exposure group were significantly higher than those in the control group,which indicated that the copper exposure could be caused by oxidative damage of the gill tissue.TNF-a,IL-6 and IL-1? levels were not significantly higher than those of the control group at 24 h,and the levels of TNF-a and IL-1? were significantly increased after 48 h in each group compared with the control group,IL-6 did not change significantly;72h,96h,the three groups of indicators compared with the control group were significantly increased,the results in acute inflammatory response in accordance with the change in the cytokine cascade process,indicating that copper can induce immune toxicity.