Abstract
Environmental estrogens have been shown to affect populations of aquatic organisms in devastating ways, including feminization of males, alterations in mating behaviors, and disruption of sexual selection. Studies have shown 17α-ethinylestradiol (EE2) exposure to induce female-like secondary sexual traits in male Gulf pipefish, changing how females perceive affected males. We aimed to understand the effects of EE2 exposure on the sex-role-reversed mating system and the strength of selection in Gulf pipefish. We used artificial Gulf pipefish breeding aggregations and microsatellite-based parentage analysis to determine maternity. We then calculated the opportunity for selection and selection differentials on body size for both sexes during three consecutive episodes of selection. Exposure to EE2 did not affect the strength of selection, likely due to the unusual sex-role-reversed mating system found in this species. With respect to multiply mated females, EE2-exposed females produced more eggs with higher embryo survivorship than nonexposed females. Thus, short-term exposure to low concentrations (2.0 ng/L) of EE2 in Gulf pipefish enhanced female reproductive success. However, higher EE2 concentrations (5.0 ng/L) caused complete reproductive failure in Gulf pipefish males. These results call for more work on the long-term effects of EE2 exposure in Gulf pipefish in artificial and natural populations.
Highlights
Endocrine disrupting chemicals can mimic natural hormones and alter bodily processes regulated by the endocrine system, causing detrimental effects on reproduction and hormone production (Orlando and Guillette 2007)
Exposure to EE2 has previously been shown to alter the mating behaviors of Gulf pipefish in binary choice tests, which suggested that EE2 could potentially disrupt the mating system and alter sexual selection
While we did find several changes in the mating system of Gulf pipefish as a result of low levels of EE2 exposure, we did not see a significant change in the strength of selection for either sex
Summary
Endocrine disrupting chemicals can mimic natural hormones and alter bodily processes regulated by the endocrine system, causing detrimental effects on reproduction and hormone production (Orlando and Guillette 2007). The earliest studies on the impacts of endocrine disruptors focused primarily on the negative physiological effects of these compounds on the reproductive systems of exposed animals, in aquatic organisms such as frogs and fish (Allen et al 1999; Iguchi et al 2001). One endocrine disruptor that has received recent attention is a synthetic estrogen found in hormonal contraceptives called 17a-ethinylestradiol, known as EE2 This contaminant is resistant to degradation in the body and ends up in the aquatic environment by passing through domestic wastewater treatment facilities and being released as a biologically active molecule in the effluent where it can accumulate to levels that cause deleterious effects on exposed organisms (Kolpin et al 2002). These high contamination levels raise questions regarding the types of effects that varying levels of EE2 exposure could have on populations of economically or ecologically important species that occupy such sites during all or part of their life cycles (Segner et al 2003; Soares et al 2009)
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