锌离子慢性暴露对中华大蟾蜍蝌蚪生长发育的影响

为评价水域环境中Zn~(2+)对两栖动物的毒性影响,本研究以中华大蟾蜍(Bufo gargarizans)蝌蚪为试验材料,对G26期蝌蚪进行了0、10、50、100和500μg·L~(-1)Zn~(2+)的慢性水体暴露直至蝌蚪发育至变态高峰期(G42期)。分别于暴露15 d和30 d后取样测定蝌蚪全长、体长、体重和发育分期各指标;此外,分析了Zn~(2+)慢性水体暴露对变态率、变态高峰期(G42)蝌蚪的全长、体长、体重、后肢长和骨骼发育的影响。结果表明:暴露15 d时,各浓度Zn~(2+)对中华大蟾蜍蝌蚪的生长发育均未造成显著影响,而持续暴露30 d后,500μg·L~(-1)Zn~(2+)处理组蝌蚪的生长发育受到显著抑制;各浓度Zn~(2+)慢性暴露均导致中华大蟾蜍蝌蚪变态率的下降,其中500μg·L~(-1)Zn~(2+)处理组的变态率最低;500μg·L~(-1)Zn~(2+)慢性暴露导致G42期中华大蟾蜍蝌蚪的形态指标(全长、体长、后肢长)和骨化程度均受到显著抑制。研究表明,水环境中高浓度锌对中华大蟾蜍幼体的生长发育和变态具有潜在的危害,水域锌污染所引发的毒理效应予以重视。

Chronic Zn2+ Exposure Induces Growth and Developmental Toxicity in Bufo gargarizans Tadpoles

Zinc (Zn) is one of the most toxic heavy metals and affects a wide spectrum of organisms.Its natural occurrence in the environment is rather low,but it is significantly increased by anthropogenic inputs,such as agricultural and industrial applications.From an ecotoxicological point of view,amphibians are useful indicators of freshwater contamination.The purpose of this study is to assess the toxic effects of zinc ion (Zn2+) on the larvae of B.gargarizans.Tadpoles were exposed to zinc (0,10,50,100 and 500 μg·L-1 Zn2+) from the beginning of larval period (G26) through metamorphic climax (G42).Firstly,total length,body length,body weight,and developmental stage of tadpoles were determined on day 15 and 30 after Zn2+ exposure.Secondly,metamorphosis and body size (total length,body length,body weight,and hind limb length) at metamorphic climax (G42) were examined.Finally,skeletal systems of tadpoles at G42 were investigated by using double staining methodology.Our results showed that Zn2+ at 500 μg· L-1 could inhibit tadpole growth and development on day 30 after Zn2+ exposure.In addition,there was a significant decline in percentage of tadpoles reaching metamorphosis climax,especially for larvae exposed to 500 μg· L-1 Zn2+.Moreover,significant reduction in tadpole size (total length,body length,and hind limb length) at G42 and deposition of calcium were observed at 500 μg· L-1 Zn2+.These results suggested that high dose exposure to Zn2+ could inhibit growth and metamorphosis of B.gargarizans.On the basis of these results,more attention should be paid to the potential impact of Zn2+on amphibian health in future.