PT17 Assessment and Remediation of Mercury Contaminated Sites
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(PT269) Methylmercury toxicity to amphibians : a sub-chronic study.

Lean, D1, Trudeau, V1, Gibson, J1, 1 Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ottawa, Ontario, Canada

ABSTRACT- This study focused on sub-chronic exposure to lethal concentrations of methylmercury for early stage amphibian tadpoles. Two species were used – wild caught Bufo americanus and laboratory bred Xenopus tropicalis. Methylmercury concentrations ranging from 1 to 1000 ng/g were spiked into a food slurry and fed to tadpoles during metamorphic development. A control food slurry was also employed. Sensitivity to methylmercury varied between species. The B. americanus study spanned 26 days and resulted in an LC50 estimate of 700 ng/g. The X. tropicalis study lasted 7 days and resulted in an LC50 estimate of 45ng/g. It was also observed that the response to methylmercury changed over the course of the experiments. At day 16-17 in the 1000 ng/g dosage, B. americanus tadpole death rate increased 11-fold. Similarly, in the 100 ng/g treatment, the rate of metamorphosis increased 4-fold in B. americanus at day 12-13. The X. tropicalis did not experience this change in response rate, as the tadpoles began dying at high rates shortly after the exposure period began and did not reach metamorphosis. This difference in sensitivity between species may be an important factor in amphibian declines worldwide._CR__LF_Funding for this project was _CR__LF_provided by NSERC, CNTC and COMERN.

Key words: Xenopus tropicalis, methylmercury, Bufo americanus, lethal concentration

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