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Aromatase inhibition in fishes with group-synchronous oocyte development: The importance of reproductive traits
Citation:
Doering, J., D. Villeneuve, B. Blackwell, J. Cavallin, A. Cole, K. Dean, K. Faye, D. Feifarek, K. Jensen, M. Kahl, A. Kittelson, C. Lalone, S. Poole, E. Randolph, C. Tilton, AND G. Ankley. Aromatase inhibition in fishes with group-synchronous oocyte development: The importance of reproductive traits. SETAC North America, Toronto, ON, CANADA, November 03 - 07, 2019.
Impact/Purpose:
This is a presentation showing that a previously developed quantitative adverse outcome pathway model based on data collected from the fathead minnow is applicable to some, but not all species of fish. Specifically, this presentation shows that the model is likely applicable to asynchronous spawning fishes, which includes many small-bodied fish such as minnows. However, the model is unlikely to be applicable to group-synchronous or synchronous spawning fishes, which includes most species including catfish, trout, and sturgeon. This work supports aims of CSS project 17.01 towards cross-species extrapolation of adverse effects towards guiding more objective ecological risk assessments of native species of ecological and economic importance in the US.
Description:
Quantitative adverse outcome pathways (qAOPs) include descriptions of quantitative response-response relationships between key biological processes to allow prediction of the probability or severity of an apical-level toxicity for a given magnitude of chemical interaction with a target biomolecule. Quantitative response-response relationships in a qAOP are intended to represent generalized patterns of responses to produce models with the broadest taxonomic applicability. However, this applicability is often untested. The present study began defining the taxonomic domain of applicability for a qAOP describing inhibition of aromatase leading to decreased fecundity developed using data from the fathead minnow. Specifically, spawning groups of Japanese medaka and zebrafish which have asynchronous oocyte development in common with fathead minnow and mosquitofish which have group-synchronous oocyte development which differs from fathead minnow were exposed to the model aromatase inhibitor, fadrozole, for 21 days. From these reproduction assays, input and output variables in the qAOP were measured in each species, including concentrations of plasma fadrozole, plasma estrogen, vitellogenin, and fecundity. The qAOP could simulate responses measured in zebrafish exposed to fadrozole with comparable accuracy as for fathead minnow, but responses measured in Japanese medaka were different. Basal levels of plasma estrogen, plasma vitellogenin, and fecundity were comparable between fathead minnow and zebrafish, but were different in Japanese medaka. Importantly, normalizing basal levels in Japanese medaka to equal those of fathead minnow enabled the qAOP to accurately predict responses to fadrozole. This suggests that quantitative response-response relationships are conserved across these three asynchronous fishes when considering relative change rather than absolute measurements. In contrast, mosquitofish have complex reproductive profiles and compensatory responses which are distinct from those of asynchronous fishes. Therefore, although responses to fadrozole were qualitatively similar between mosquitofish and fathead minnow, the current qAOP could not quantitatively predict responses in this group-synchronous fish. Overall, this study illustrates the importance of reproductive traits, including oocyte development and basal levels of biomolecules, in the species extrapolation of certain quantitative response-response relationships described in qAOPs.