Quantification and assessment of xenoestrogenic exposure in Fundulus heteroclitus in Long Island Sound

Date of Completion

January 2005

Keywords

Biology, Animal Physiology

Degree

Ph.D.

Abstract

Fundulus heteroclitus was used in this research to study the physiological effects of exposure to xenoestrogens (XEs). Xenoestrogens (XEs) are part of a larger class of compounds known as endocrine disrupting chemicals (EDCs). Examples of the feminizing effects of such compounds have been found in many species in the wild and include ovotestes and decreased levels of serum sex steroid levels. In this study, exposure to XEs was assessed through the quantification of vitellogenin (Vtg) levels, CYP 1A1 activity, and gonadal and hepatic morphology. ^ In the laboratory exposure portion of this study, F. heteroclitus were exposed to 17β-estradiol (E2) and nonylphenol (NP) by i.p. injection. Dose-responsive Vtg induction was detected by a competitive ELISA. CYP 1A1 activity did not exhibit a particular trend and did not appear to be correlated to Vtg induction. ^ Four sites on Long Island Sound were selected for the field study based on published data concerning levels of xenoestrogens: Barn Island (reference), Bluff Point and Hammonassett (moderately contaminated) and Milford (highly contaminated). The assays (ELISA and EROD) authenticated by the lab exposure study were utilized. Additionally, the liver and gonads were harvested for histological examination. No significant differences were detected in Vtg levels of Fundulus heteroclitus from Long Island Sound, although levels were highest at the reference site (Barn Island) and lowest at the highly contaminated site (Milford). In general. CYP 1A1 activity was inversely correlated to Vtg induction, although CYP 1A1 activity was anomalistically high at the reference site. Histological examination of the liver and gonads revealed normal morphology. Interestingly, significant site-based differences in the degree of parasite infestation of the liver were detected. Similar to Vtg levels, the highest values were found at the reference site (Barn Island) and the lowest values were observed at the highly contaminated site (Milford). ^ This research supports the fact that the appropriate tools have been developed to quantify xenoestrogenic exposure of Fundulus heteroclitus in Long Island Sound. The difference in observed effects between the lab exposure and field study may be explained by the fact that fish are exposed to a cocktail of contaminants in the wild. Physiological effects of this exposure have been detected in Long Island Sound at the organismal level. It is possible that exposure to XEs may effect the population level of F. heteroclitus. ^

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