Date Awarded

2001

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Abstract

Vitellogenin (VTG) is widely used as a biomarker for environmental estrogens and reproductive disruption in fish. Vitellogenesis is the process by which yolk is formed. The endpoint is most sensitive in male fish where vitellogenesis is an abnormal process. Research examining effects of environmental mixtures of chemicals (e.g. creosote) on vitellogenesis is limited. This study examines plasma VTG expression in both male and female mummichog, Fundulus heteroclitus, collected from a creosote-contaminated site and two reference sites in lower Chesapeake Bay, USA, and in wild-caught male reference fish exposed in the laboratory to creosote-contaminated sediment. Further, this study uses tissue somatic indices (gonadosomatic index, hepatosomatic index, and condition factor) as organ-level indicators of reproductive status and creosote exposure. Western blotting with an anti-vitellogenin monoclonal antibody (FY 10- 9) was used to identify an abundant (approx. 218 kDa) protein in F. heteroclitus plasma samples. Vitellogenin was not observed in any male fish collected from any of the field sites. No sitespecific differences were observed in plasma VTG of females from these sites. Overall, fish from the creosote-contaminated site appear resilient and reproductively fit. After seven days of exposure, reference fish exposed to sediment from the creosote-contaminated site suffered extensive mortality (approx. 25% ), but displayed no expression of VTG and had no alterations in other measured indices except for increased hepatosomatic index and induction of the biotransformation enzyme, cytochrome P4501A (CYPlA). Lack of response in Atlantic Wood fish could be due to: (1) physiological adaptation of the population from the creosotecontaminated site to creosote exposure (2) species-specific sensitivity (3) creosote not exerting estrogenic effects and regulating vitellogenesis. Thus, while VTG has been used successfully as a practical and reliable screening method for wildlife toxicity, results herein do not support use of this biomarker for F. heteroclitus from creosote-contaminated sites. This study does reaffirm constituents of creosote binding to the aryl hydrocarbon receptor resulting in induction of CYP IA. More attention needs to be given to developing alternative biomarkers not sensitive to aryl hydrocarbon-mediated antiestrogens if detection of weak estrogens and reproductive disruption in creosote and other complex mixtures is to be achieved.

DOI

https://dx.doi.org/doi:10.25773/v5-dzx1-cc28

Rights

© The Author

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