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Environmental hormones and their impacts on sex differentiation in fathead minnows
Citation:
Leet, J., S. Sassman, J. Amberg, A. Olmstead, L. Lee, G. Ankley, AND M. Sepulveda. Environmental hormones and their impacts on sex differentiation in fathead minnows. AQUATIC TOXICOLOGY. Elsevier Science Ltd, New York, NY, 158:89-107, (2015).
Impact/Purpose:
Runoff from lands fertilized with animal manure from concentrated animal feeding operations (CAFOs) is a source of hormones to surface water. In this study we tested the hypothesis that juvenile fathead minnows exposed to sex steroids singly and in a “typical” CAFO mixture while undergoing sex differentiation would respond with changes in the expression of a set of target genes leading to gonadal abnormalities later in life. A static daily-renewal system was used to expose juveniles (10 to 20 days post-hatch, dph) to 17β-trenbolone (17β-TRB, 5 ng/L) or ethinyl estradiol (EE2, 5 ng/L). In a second experiment, fish were exposed (0-45 dph) in a flow-through system to a CAFO mixture composed of steroids and degradates (2 – 16 ng/L), atrazine and degradates (15 – 250 ng/L), and nitrate (3 – 11 mg/L). In the single hormone experiment, expression of genes involved in steroidogenesis (cyp19a, cyp17, and star) was decreased in females. In contrast, no differences in gene expression were observed in fish exposed to the CAFO mixture. The majority (84%) of treated males, however, had testes containing an ovarian cavity, indicative of feminization. Overall, our results show that: (1) changes in gene expression after single hormone exposures are sex-specific, with females being more responsive than males; and (2) phenotypic alterations in testicular development can be elicited by a “CAFO” mixture when fathead minnows are exposed during the first 45 d of development.
Description:
Runoff from lands fertilized with animal manure from concentrated animal feeding operations (CAFOs) is a source of hormones to surface water. To test the hypothesis that juvenile fathead minnows exposed to sex steroids singly and in a “typical” CAFO mixture while undergoing sex differentiation will respond with changes in the expression of a set of target genes leading to gonadal abnormalities later in life. A static daily-renewal system was used to expose juveniles (10 to 20 days post-hatch, dph) to 17â-trenbolone (17â-TRB, 5 ng/L) or ethinyl estradiol (EE2, 5 ng/L). In a second experiment, fish were exposed (0-45 dph) in a flow-through system to a CAFO mixture composed of steroids and degradates (2 16 ng/L), atrazine and degradates (15 250 ng/L), and nitrate (3 11 mg/L). In the single hormone experiment, expression of genes involved in steroidogenesis (cyp19a, cyp17, and star) was decreased in females. In contrast, no differences in gene expression were observed in fish exposed to the CAFO mixture. The majority (84%) of treated males, however, had testes containing an ovarian cavity, indicative of feminization. Overall, our results show that: (1) changes in gene expression after single hormone exposures are sex-specific, with females being more responsive than males; and (2) phenotypic alterations in testicular development can be elicited by a “CAFO” mixture when fathead minnows are exposed during the first 45 d of development.
