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Is a Frog a Fish with Lungs? A Case Study of the Fungicide Trifloxystrobin
Citation:
Lavelle, C., C. Lilavois, P. Harris, N. Zielinski, M. Hamilton, H. Skowronski, Sandy Raimondo, AND J. Awkerman. Is a Frog a Fish with Lungs? A Case Study of the Fungicide Trifloxystrobin. SETAC North America 38th Annual Meeting, Minneapolis, MN, November 12 - 16, 2017.
Impact/Purpose:
An early life stage study of the comparative toxicity of the pesticide trifloxystrobin was conducted in a model fish and frog species. This is part of a larger project to evaluate the use of fish as a surrogate species for amphibians in risk assessments and develop tools to translate laboratory effects into population models for native species. This research will be of interest to the eco-toxicology scientific community as well as to environmental risk assessors and managers.
Description:
Current risk assessment practice is to use fish as a surrogate for larval stage amphibian species in determining chemical sensitivity when data for amphibians is not available. While evidence exists that fish are a sufficiently sensitive surrogate for amphibians for a wide range of chemicals, there may be cases where this approach is inadequate. Of important consideration is the drastic life history differences between model fish species and amphibians which must undergo the complex process of metamorphosis. As pesticide exposure has been suggested to contribute to amphibian population decline it is important to determine if this form of surrogacy in risk assessment evaluations is protective of amphibian populations. In this study, zebrafish (Danio rerio) and African clawed-frog (Xenopus laevis) embryos (< 24 hpf) were exposed to 0 – 200 μg/L trifloxystrobin (0.005 % acetone) for 10 days in a static renewal system. Both species were monitored daily for mortality, developmental abnormalities, hatching and pigmentation. On day 10, individuals were weighed, photographed for length measurements, and flash frozen for future gene expression studies. Log-logistic 96-hr LC50 curves for D. rerio and X. laevis show that X. laevis is more sensitive to trifloxystrobin exposure than D. rerio with LC50 values of 45.85 ± 3.98 μg/L and 135.86 ± 7.58 μg/L, respectively. While a delay in hatching and pigmentation was observed in D.rerio no effects on growth were observed. Conversely, a dose-dependent decrease in weight and a delay of development were observed in X. laevis as fewer trifloxystrobin tadpoles reached NF stage 50 by the experiment termination than control tadpoles. Tissues collected from this study will be used to elucidate a molecular basis for species sensitivity comparison by assessing differential gene expression and guiding future comparative toxicology studies.