Assessment of the Risk of Solar Ultraviolet Radiation to Amphibians. I. Dose-Dependent Induction of Hindlimb Malformations in the Northern Leopard Frog (Rana pipiens)

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• 作者：Gerald T. Ankley ; Stephen A. Diamond ; Joseph E. Tietge ; Gary W. Holcombe ; Kathleen M. Jensen ; David L. DeFoe ; and Ryan Peterson
• 刊名：Environmental Science & Technology
• 出版年：2002
• 出版时间：July 1, 2002
• 年：2002
• 卷：36
• 期：13
• 页码：2853 - 2858
• 全文大小：89K
• 年卷期：v.36,no.13(July 1, 2002)
• ISSN：1520-5851

文摘

A number of environmental stressors have been hypothesizedas responsible for recent increases in limb malformationsin several species of North American amphibians. The purposeof this study was to generate dose-response datasuitable for assessing the potential role of solar ultraviolet(UV) radiation in causing limb malformations in a speciesin which this phenomenon seemingly is particularlyprevalent, the northern leopard frog (Rana pipiens). Frogswere exposed from early embryonic stages throughcomplete metamorphosis to varying natural sunlight regimes,including unaltered (100%) sunlight, sunlight subjected toneutral density filtration to achieve relative intensities of 85%,75%, 65%, 50%, and 25% of unaltered sunlight, andsunlight filtered with glass or acrylamide to attenuate,respectively, the UVB (290-320 nm) and UVB plus UVA (290-380 nm) portions of the spectrum. The experiments wereconducted in a controlled setting, with continual monitoringof UVB, UVA, and visible light to support a robust exposureassessment. Full sunlight caused approximately 50%mortality of the frogs during early larval development; nosignificant treatment-related mortality occurred under any ofthe other exposure regimes, including 100% sunlightwith glass or acrylamide filtration. There was a dose-dependent (p < 0.0001) induction of hindlimb malformationsin the frogs, with the percentage of affected animalsranging from about 97% under unaltered sunlight to 0% inthe 25% neutral density treatment. Malformations werecomprised mostly of missing or truncated digits, and generallywere bilateral as well as symmetrical. Filtration ofsunlight with either glass or acrylamide both significantlyreduced the incidence of malformed limbs. The estimatedsunlight dose resulting in a 50% limb malformation rate (ED50)was 63.5%. The limb ED50 values based on measuredsunlight intensities corresponded to average daily dosesof 4.5 and 100 Wh·m^-2 for UVB and UVA, respectively.Exposure to sunlight also resulted in increased eyemalformations in R. pipiens; however, the dose-responserelationship for this endpoint was not monotonic. Theresults of this study, in conjunction with measured orpredicted exposure data from natural settings, provide abasis for quantitative prediction of the risk of solar UV radiationto amphibians.