Physiological Responses of the Fathead Minnow (<em>Pimephales</em> <em>promelas</em>) to Anthropogenic Sources of Endocrine Disruptors

Abstract

Anthropogenic sources of endocrine disrupting compounds (EDCs) are prevalent in aquatic ecosystems. As a result, these compounds target the most vulnerable physiological mechanisms of reproductive development in fish. The main focus of this study was to assess the impact of two sources of EDCs; a single potent EDC, 17α-ethinylestradiol (EE2), as well as an agricultural source of an EDC mixture, poultry litter leachate, on the reproductive processes of the fathead minnow, <em>Pimephales</em> <em>promelas</em>. The experimental paradigms included a 21-day laboratory reproductive assay, a larval exposure including a depuration step until 8 months of age to determine the response in the adult animal, and a whole-organism, partial life-cycle assessment of reproductively active adult fish and development of their offspring.

In the first experiment, breeding groups of fathead minnow were exposed to 0, 10, and 40 ng/L of EE2 for 21 days. A significant decrease in testosterone (T), the 17β-estradiol (E2)/T ratio and 11-ketotestosterone in males was observed in the 10 ng/L and 40 ng/L EE2 treatments compared to the control. Male secondary sex characteristics declined with increasing concentrations of EE2. Moreover, 43% of the males in the highest EE2 group (40 ng/L EE2) developed ovipositors. In experiment two, E2 was detected at approximately 200-400 pg/mL and T at approximately 100-400 pg/mL in the poultry litter leachate. Gender ratio was skewed toward female in the two highest concentrations of the poultry litter leachate treatment groups. In experiment three, with a transgenerational design, adult fish had reduced fecundity and males had a significant reduction in male traits when exposed to poultry litter leachate. Vitellogenin production was observed in male fish. In the offspring, both the Low and E2 fish from the same treated adults had significantly lower GSI values and aromatase activity levels. Exploration of different developmental stages and exposures across generations improves our understanding of the impact anthropogenic EDCs can have on wild fish populations.