The number of potential applications for manufactured nanomaterials (NMs) is growing exponentially around the world, without concomitant research into the possible consequences of inadvertent or purposeful releases into the environment. Fish and other aquatic organisms reside in bodies of water where NMs are likely to be disposed. A growing body of evidence suggests that some NMs, depending on their composition, size or surface functionalization, can affect fish health. The goal of this study is to evaluate if NMs can interfere with fish reproductive behavior. This project is important because alterations in behavior can have devastating genetic and population effects. The research proposed here will fill a large gap in the understanding of the ecotoxicological implications of engineered NMs that may be released into the environment. Ultimately, studies like this one will influence NM development by clearly defining the characteristics that make NMs bio-active and that should be considered in manufacturing and future environmental regulatory policies.
The overarching goal of this thesis research is that NMs introduced into fish orally through gavage can penetrate through the intestine into the blood stream and then partition into organs where they can further impact with cellular mechanisms including steriodogenesis. Orally dosed quantum dots (QDs) cross the gut epithelium and accumulate in various tissues including the gonads, suggesting they may have profound effects on tissue function. This project will specifically address a new hypothesis that NMs are able to interfere with reproductive behaviors of fathead minnows. It is known that endogenous or exogenous steroid hormones control reproductive behavior of fish. The specific hypotheses to be tested are (A) that functionalized QDs will be internalized into testis and interfere with steroidogenesis and alter male reproductive behavior, and (B) that single walled carbon nanotubes will bind and sequester exogenously added ethinylestradiol and inhibit feminization of male behavior. These hypotheses will be tested using in vivo studies to determine the interactions between NMs and environmental estrogen (EE) on gene expression and competitive reproductive behavior in fathead minnows, Pimephales promelas. The expected outcomes are that (1) SWCNTs will reduce EE bioavailability and ultimately alter nest holding and defending behavior, (2) QDs will cause reproductive behavioral deficits in FHMs, and (3) that the effects produced by QDs will be exacerbated by EE co-exposure.
