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Endocrine Disrupters Study
An extensive review of the literature on the effects of endocrine disrupters on fish has been synthesized by Chemical Impacts Team (CIT) researchers. A primary conclusion of this synthesis is that overt endocrine disruption in fish at least in the U.S. does appear to be not a ubiquitous environmental phenomenon but more likely to occur near outfalls from sewage treatment plants, pulp/paper mills and industrial activities. While there is evidence of severe effects in fish in some areas, there is no clear indication that large populations of fish are being affected by endocrine disrupters.
To provide additional information on this issue, COAST scientists conducted a survey and laboratory study was completed in selected tributaries of the Chesapeake Bay, to assess possible reproductive endocrine disruption in the killifish Fundulus heteroclitus. Seven field sites representing a variety of land use activities, ranging from relatively pristine to industrialized areas near Baltimore, were established.
Male and female fish were sampled for a period of two years. Sampling occurred during the fall months after reproduction had ceased, and again in the spring/summer, the peak reproductive period for this species. All spring/summer sampling occurred within 2 days of the full moon to coincide with the species' lunar spawning cycle. Parameters measured included plasma vitellogenin, as well as certain gonadal and hepatic indices along with gonadal histologic analysis. Vitellogenin was analyzed by direct Enzyme Linked ImmunoSorbent Assay (ELISA) using a monoclonal antibody prepared by the University of Florida.
Eighty-six percent of the male fish sampled, however, contained no detectable vitellogenin as determined by the ELISA. In all cases except one, levels of vitellogenin were low, in the range of 0.01 - 0.09 mg/ml. As a comparison, reproductive female F. heteroclitus typically contain between 12 and 16 mg/ml plasma vitellogenin. There were no significant differences in vitellogenin concentrations in males between sites, and there were occasional positive detections of vitellogenin in males from the pristine sites.
A second species of fish, the sheepshead minnow (Cyprinodon variegatus) was also collected at three sites where F. heteroclitus was taken (reference and two contaminated sites). An analysis of vitellogenin in male sheepshead minnows revealed no significant difference in vitellogenin levels compared with F. heteroclitus.
Although there were no apparent estrogenic effects, there was some evidence of antiestrogenic and antiandrogenic effects at certain sites. The gonadal index in male and female fish from Baltimore , for example, was significantly lower than fish from the reference site. Additionally, females from Baltimore had vitellogenin levels significantly lower than the reference site. Data on sediment contaminant concentrations for the Baltimore locations as well as a reference site were obtained from published databases. An analysis of the data revealed that lower vitellogenin levels and gonadal indices in female F. heteroclitus were negatively and significantly correlated with sediment PAH concentrations, and lower gonadal indices in males were negatively correlated with sediment concentrations of PAHs and PCBs. Histologic examination of gonadal sections, however, failed to reveal any ovotestes in the fish examined, and also failed to reveal any major differences in gonadal measurements made on fish between sites.
Project Partners
University of Florida
University of Maryland
References
Endocrine Disruption in Fish: An Assessment of Recent Research and Results