Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, USA.
Environ Toxicol Chem. 2012 Jul;31(7):1587-94. doi: 10.1002/etc.1849. Epub 2012 May 18.
Exposure to environmental contaminants contributes to the global decline of amphibian populations. The impacts of organic contaminants on amphibians are well documented. However, substantially less is known concerning the potential effects of metals on amphibian populations. Copper (Cu) is an essential element, but it can be toxic at concentrations only slightly higher than the normal physiological range. The present study examines the effects of chronic Cu exposure on embryos and larvae of southern leopard frogs, Lithobates (Rana) sphenocephalus. Groups of eggs from multiple clutches were collected from two wetlands and exposed to a range of Cu concentrations (0-150 µg/L) until they reached the free-swimming stage, and then individual larvae were reared to metamorphosis. Higher Cu concentrations significantly reduced embryo survival to the free-swimming stage but did not further reduce survival to metamorphosis. Larval period was affected by Cu treatment, but the clutch from which larvae originated (i.e., parentage) explained a higher proportion of the variation. Embryo survival to hatching varied significantly among clutches, ranging from 42.9 to 79.2%. Measurable levels of Cu were found in larvae with body burdens up to 595 µg Cu/g dry mass in the 100 µg/L treatment, and larval Cu body burdens were higher than in metamorphs. The present study also demonstrated that higher initial egg density ameliorated embryo mortality at higher Cu levels and should be accounted for in future studies.
环境污染物的暴露导致全球两栖动物种群数量下降。有机污染物对两栖动物的影响已有充分的记录。然而，对于金属对两栖动物种群的潜在影响，人们知之甚少。铜 (Cu) 是一种必需元素，但在浓度仅略高于正常生理范围时就可能有毒。本研究检查了慢性 Cu 暴露对南方豹蛙 Lithobates (Rana) sphenocephalus 的胚胎和幼虫的影响。从两个湿地收集了多批卵，并将其暴露于一系列 Cu 浓度（0-150μg/L）中，直到它们达到自由游动阶段，然后将单个幼虫饲养至变态期。较高的 Cu 浓度显著降低了胚胎发育到自由游动阶段的存活率，但不会进一步降低到变态期的存活率。Cu 处理影响幼虫期，但幼虫的起源（即亲代）解释了更多的变异。卵孵化的胚胎存活率在不同批次之间差异显著，范围从 42.9%到 79.2%。在 100μg/L 处理中，体内负荷高达 595μg Cu/g 干重的幼虫中发现了可测量水平的 Cu，并且幼虫的 Cu 体负荷高于变态期的 Cu 体负荷。本研究还表明，较高的初始卵密度可减轻高 Cu 水平下的胚胎死亡率，在未来的研究中应加以考虑。
