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Comparative Toxicity of Model Fish and Amphibian to Trifloxystrobin Early Life Stage Exposures
Citation:
Lavelle, C., J. Awkerman, P. Harris, C. Lilavois, N. Zielinksi, H. Skowronski, M. Frazier, E. Moso, A. Brennan, D. MacMillan, AND Sandy Raimondo. Comparative Toxicity of Model Fish and Amphibian to Trifloxystrobin Early Life Stage Exposures. 2021 Society of Toxicology Annual Meeeting, Virtual, FL, March 12 - 26, 2021.
Impact/Purpose:
An early life stage study of the comparative toxicity of the fungicide trifloxystrobin was conducted with a model frog and two model fish species. This is part of a larger project to evaluate the use of fish as 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 ecotoxicology scientific community as well as to environmental risk assessors and managers.
Description:
Chemical exposures that lead to adverse developmental effects of individuals in could result in significant population-level impacts. Current risk assessment practices use early life stage fish data when information for larval amphibians are not available. While fish are sufficiently sensitive to a range of chemicals for screening-level evaluation, developmental delays could have relatively greater impacts on subsequent amphibian life stages that are not represented by fish. As pesticide exposure contributes to amphibian population declines, it is important to understand the uncertainties of species surrogacy in risk assessments aimed at protecting amphibians. Strobilurin fungicides are an economically important class of pesticides designed to inhibit the mitochondrial respiratory chain ultimately interfering with ATP production. Trifloxystrobin (TX), a widely applied strobilurin, is frequently detected in aquatic systems, often at levels known to cause sub-lethal toxicity in a range of species. In this study we conducted the first side by side comparison of 10-day early life stage exposures conducted on zebrafish (Danio rerio), fathead minnow (Pimephales promelas), and African clawed-frog (Xenopus laevis) to TX to determine if growth, development, and gene expression changes were similarly altered across species. Mortality data suggests that acute toxicity values derived from D. rerio are not ideal surrogates for lethality in X. laevis. While a delay in hatching was observed in both fish species, weight and length were only reduced in P. promelas. A dose-dependent decrease in weight and a developmental delay were observed in X. laevis. Here, we also report the first investigation of gene expression changes in P. promelas and an amphibian species following exposure to a strobilurin. Tissues collected from exposed individuals were used to compare differential gene expression on targets related to endocrine signaling, oxidative and general stress response, and apoptosis. Gene expression patterns suggest that biological pathways are perturbed by TX exposure in a species-specific manner. Future studies will examine the potential of the observed changes in gene expression to be predictive of more population-relevant endpoints, such as time to metamorphosis.
