title: Chronic toxicity of copper on embryo development in Chinese toad, Bufo gargarizans.
abstract: This study examined the effects of copper exposure on embryonic development of Chinese toad, Bufo gargarizans. Firstly, the LC(50) values from 24 to 96 h of exposure were 3.61×10(-6) M, by means of a 4 d toxicity test with B. gargarizans embryos. Secondly, Chinese toad embryos were exposed to 10(-9)-10(-6) M copper from mid gastrula stage to operculum completion stage. Measurements included mortality, tadpole weight, tadpole total length, growth retardation, duration of different embryo stages and malformation. Embryonic survival was not affected by copper. Relative to control tadpoles, significantly decreased weight and total length were found at 10(-9)-10(-6) M reduced percentage of the embryos in right operculum stage after 10 d exposure to copper and reduced percentage of embryos in operculum completion stage after 12 d exposure to copper were also observed. Moreover, the duration of embryonic development increased at neural, circulation and operculum development stage in copper-treated groups. For the scanning microscope and histological observation, the abnormalities were malformation of wavy dorsal fin, flexural tail, curvature body axis, yolk sac oedema and reduced pigmentation in the yolk sac. Histopathological changes in olfactory, retinal epithelium and skin were also observed. DNA strand breaks exposed to the copper were analyzed by DNA ladder. In conclusion, copper induced toxic effects on B. gargarizans embryos. The present study indicated chronic toxicity tests may provide more accurate way in formulating the "safe levels" of heavy metals to amphibian.
authors.affiliation: College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Xia
authors.forename: Hongfeng
authors.initials: H
authors.lastname: Zhao
authors.forename: Minyao
authors.initials: M
authors.lastname: Wu
authors.forename: Hongyuan
authors.initials: H
authors.lastname: Wang
mesh_terms: D000818:Animals; D002025:Bufonidae / Q000196:embryology* / Q000254:growth & development; D002681:China; D003300:Copper / Q000633:toxicity*; D004249:DNA Damage / Q000187:drug effects; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000187:drug effects*; D005260:Female; D007814:Larva / Q000187:drug effects; D009830:Olfactory Bulb / Q000473:pathology; D012160:Retina / Q000187:drug effects; D012867:Skin / Q000187:drug effects; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D003300:Copper