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The effects of extreme concentrations of toxic metalloids, such as arsenic and antimony, on larval amphibians are not well understood. 

To better comprehend anuran tadpole tolerance to extreme environmental arsenic and antimony concentrations, researchers sampled Western toad tadpoles throughout their development in wetlands contaminated from the Stibnite Mine in central Idaho. Although the tadpoles completed metamorphosis, they accumulated among the highest concentrations of arsenic and antimony ever reported for a living vertebrate. Metalloids were initially concentrated in the gut primarily by ingestion of contaminated sediment; however, by metamorphosis, the highest levels were found in other tissues. Sub-lethal effects, including delayed development and reduced size at metamorphosis, were associated with elevated metalloid exposure. Organic forms of arsenic in tadpole tissues suggest they can biomethylate inorganic arsenic compounds, which could contribute to their tolerance to extremely elevated metalloid concentrations. Findings demonstrate remarkable tolerance of toad tadpoles to extreme metalloid exposure and implicate physiological processes mediating that tolerance.

Dovick, M.A., Arkle, R.S., Kulp, T.R., Pilliod, D.S., 2020, Extreme arsenic and antimony uptake and tolerance in toad tadpoles during development in highly contaminated wetlands: Environmental Science and Technology,

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