Effects of 17α-ethynylestradiol on early-life development, sex differentiation and vitellogenin induction in mummichog (Fundulus heteroclitus)

Department of Biology and Canadian Rivers Institute, University of New Brunswick, Saint John, NB, Canada.
Marine environmental research (Impact Factor: 2.76). 10/2009; 69(3):178-86. DOI: 10.1016/j.marenvres.2009.10.002
Source: PubMed


Fertilized mummichog eggs retrieved from 17α-ethynylestradiol (EE2) exposed adult fish were raised in concentrations of EE2 ranging from 0 to 100 ng/L (100 ng/L EE2 estimated to have actual average exposure concentrations of 30% of nominal; 0.1-10 ng/L were below detect throughout 24-h exposure period) for 61 weeks post-hatch. Eggs exposed at 100 ng/L hatched sooner, the larvae were longer, and survival of juvenile fish from hatch to study termination was greater than all other treatments, though fewer hatched at this treatment. Sex ratios were skewed (>80% female phenotype) at 100 ng/L EE2, and some gonadal male fish displayed female secondary sex characteristics. Condition factor, gonadosomatic index (GSI), and liver somatic index (LSI) were found to decrease in both sexes between 52 and 61 weeks post-hatch. Female fish had increased hepatic vitellogenin (VTG) at 52 weeks post-hatch. When exposed to 1, 10 and 100 ng/L EE2, female fish had a higher proportion of vitellogenic follicles in the ovarian tissue. Males exposed at 100 ng/L may have had disruption at some endpoints (GSI, VTG) that is masked due to reduced sample size compared to other treatments. Fish exposed to concentrations of EE2 at or below 10 ng/L showed inconsistent effects on development and reproductive potential. This study indicates the potential for population-level effects at the high range of environmental EE2 at concentrations equivalent to those at which consistent effects in fecundity in the adult mummichog reproductive test have been measured. This work demonstrates that chronic EE2 exposure causes developmental effects at concentrations similar to those which cause effects in the shorter-term adult mummichog reproductive test. Effects are at higher concentrations than have been noted for freshwater model species. Whether this is because of species sensitivity or due to differences between freshwater and saltwater availability of EE2 or its uptake requires further study.

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    • "Most studies analyzing the effect of exposure of aquatic vertebrates to EE2, focus in its effects as an endocrine disruptor, and its toxic potential effects to various organisms has been extensively studied (Aris et al., 2014). The most extensive studies have been performed with, and many alterations have been observed, including the increase of plasma vitellogenin in males and females, accelerated proportions of intersex fish, decreased egg and sperm production, reduced gamete quality, complete feminization of male fish, reduced fertility and fecundity, morphological and physiological hepatic alterations, and also behavioral changes (Larsson et al., 1999; Notch et al., 2007; Pawlowski et al., 2004; Peters et al., 2010; Reyhanian et al., 2011; Saaristo et al., 2010; S arria et al., 2011; Scholz and Gutzeit, 2000). Nevertheless, there are also some studies analyzing the effects of EE2 on amphibians, including effects on metamorphosis and alteration in the sex ratios, as demonstrated to Lithobates pipiens tadpoles (Hogan et al., 2008) and to Xenopus laevis (Tompsett et al., 2012). "
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    ABSTRACT: This study evaluated if a concentration of 17α-ethinylestradiol (EE2 - 10 ng L(-1) for 96 h) normally found in Brazilian surface waters exerts any impact on cardiac function of bullfrog tadpoles (25 Gosner stage), Lithobates catesbeianus. During exposure, the animals' activity level (AL -% of active individuals) was monitored twice a day. Then, the in loco heart rate (fH - bpm) was determined, as well as the relative ventricular mass (RVM - % of body mass). Afterwards, cardiac ventricles were mounted for isometric force recordings (CS - mN mm(-2)), and determination of the cardiac pumping capacity (CPC - mN mm(-2) min(-1)). EE2 did not affect tadpoles' AL, although it resulted in a tachycardia in animals exposed to EE2 (fH = 66 bpm) when compared to controls (fH = 52 bpm), suggesting that EE2 acts directly on the cardiac muscle of tadpoles, rather than being a result of an increased cardiac demand due to a higher activity level (i.e., avoidance response). Additionally, EE2 exerted a positive inotropic response, which resulted in a higher CPC, which occurred independently of an increase in the number of myofibrils of EE2-exposed animals, since RVM remained similar between experimental groups. Thus, the increase on cardiac demand induced by the exposure to EE2 elevates considerably the animal energy expenditure, diverting a large amount of energy that tadpoles could use for their growth and development. These alterations can make amphibians more susceptible to predators and reduce the likelihood to reach reproductive stage.
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    • "Chronic exposure of adult mummichog to EE 2 and their offspring resulted in reduced spawning, fertilization and hatching (Peters et al., 2007), as well as altered sex ratios and gonadal development in the offspring (Peters et al., 2010). EE 2 appears to elicit effects in adult mummichog at concentrations greater than have been shown for freshwater species [e.g., fathead minnow (Pimephales promelas ), Japanese medaka, zebrafish], which tend to respond to more environmentally relevant EE 2 concentrations (0.1–10 ng/L) (Nash et al., 2004; Balch et al., 2004; Parrott and Blunt, 2005). "
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