SYMPOSIUM Creating Females? Developmental Effects of 17-Ethynylestradiol

Synopsis Interest in the occurrence and fate of trace organic contaminants in the aquatic environment and their potential effects on all organisms has increased over the past two decades. Researches on contaminants have included both natural and synthetic estrogenic contaminants, neuroactive pharmaceuticals, and other endocrine disrupting chem-icals that are mediated by the androgen and progesterone receptors. Exposure to very low concentrations (ng/L or parts per trillion) of compounds such as 17-ethynylestradiol (EE2), a synthetic estrogen, can affect gonadal development, viability and production of eggs, fertilization rate, and sexual differentiation in fishes. Researchers and aquaculturists have used exposures to relatively higher concentrations of androgens and estrogens, for example 17-methyltestosterone and EE2, respectively, to direct sexual differentiation in a number of fishes. Rivulus is an androdioecious teleost that in nature exists mostly as selfing, simultaneous hermaphrodites as well as a small number of males that outcross with hermaph-rodites. No one has either collected females in the wild or created functional females in the laboratory. This study had two goals: (1) to develop a reliable protocol to produce female rivulus to enable downstream technologies such as embryo injections and (2) to investigate developmental effects of EE2 on the sexual outcome, reproductive health, and relevant gene expression in rivulus. With these goals in mind, we exposed newly hatched rivulus to nominal concentrations of 0.1, 0.5, or 1.0 parts per million (ppm) EE2 for 4 weeks, grew them to maturity in control water, and then compared egg production; production and viability of embryos; age of reproductive maturity; and gene expression in the brain, gonad