Female Reproductive Impacts of Dietary Methylmercury in Yellow Perch (Perca flavescens) and Zebrafish (Danio rerio)

This study sought to evaluate the effects of dietary MeHg exposure on adult female yellow perch (Perca flavescens) and zebrafish (Danio rerio) reproduction by relating controlled exposures with subsequent reproductive effects. Yellow perch were used in the study for their socioeconomic and ecological importance within the Great Lakes basin, and the use of zebrafish allowed for a detailed analysis of the molecular effects of MeHg. MeHg exposures at environmentally relevant levels were done in zebrafish for a full life cycle, mimicking a realistic exposure scenario, and in adult yellow perch for twenty weeks, capturing early seasonal ovarian development. In zebrafish, several genes involved in reproductive processes were shown to be dysregulated by RNA-seq and QPCR, but no significant phenotypic or physiological changes were observed with ovarian staging, fecundity, or embryo mortality. Yellow perch did not appear to be affected by MeHg, either at a molecular level, as assessed by QPCR of eight genes in the pituitary, liver, and ovary tissue, or a physiological level, as seen with ovarian somatic index, circulating estradiol, and ovarian staging. Lack of impact in yellow perch limits the usefulness of zebrafish as a model and suggests that the reproductive sensitivity to environmentally relevant levels of MeHg differs between yellow perch and zebrafish. Overall design: 12 samples of total RNA isolated from adult zebrafish ovaries were analyzed. Each exposure group (1, 3, and 10 ppm MeHg) had three replicates, as did the vehicle control. Each sample was comprised of pooled total RNA of up to 6 individual fish.

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DeBofsky AR, Klingler RH, Mora-Zamorano FX, Walz M, Shepherd B, Larson JK, Anderson D 3rd, Yang L, Goetz F, Basu N, Head J, Tonellato P, Armstrong BM, Murphy C, Carvan MJ 3rd