Reproductive endocrine disruption in the killifish Fundulus heteroclitus in the Chesapeake Bay (Maryland)

Concern has been raised that a variety of environmental contaminants, termed endocrine disrupters have the ability to mimic or antagonize the action of endogenous hormones, with potentially serious implications for wildlife and humans. In this research, reproductive endocrine disruption was assessed in the killifish Fundulus heteroclitus, a common inhabitant of the Chesapeake Bay.; Laboratory experiments were carried out to assess the response of male F. heteroclitus to known endocrine disrupting compounds (EDCs). A held study was conducted to determine if reproductive endocrine disruption is common in this species. Eight sites representing pristine, industrial, urban, and agricultural areas were sampled. Parameters measured included the egg protein vitellogenin, gonadosomatic (GSI) and hepatosomatic (HSI) indices, gonadal histology, and male/female ratios.; Vitellogenin was the most sensitive biomarker. Production occurred in a dose-dependent manner in males exposed to 4-nonylphenol, 4-( tert-octyl)phenol, bisphenol-A, and 17β-estradiol. Unlike the GSI, induction of vitellogenin was not influenced by season. There was some evidence that fish from contaminated areas produced less vitellogenin than those from a pristine habitat.; In the field, there was no evidence of estrogenic endocrine disruption. Vitellogenin was only occasionally (14%) detected in males, and did not differ between sites or seasons. When detected, vitellogenin in males was at least an order of magnitude lower than in spawning females.; There was some evidence of antiestrogenic and antiandrogenic effects. Lower GSIs in males and females, and lower vitellogenin in females was correlated with sediment contaminants, primarily in Spring 1999. Gonadal anomalies in F. heteroclitus were minor and included slight declines in gonadal tissues (male and female) in fish from contaminated sites. In general, few differences were found between sites in the fall, the time of natural gonadal regression in F. heteroclitus. Male to female ratios were usually close to expected distributions. Overall, reproductive endocrine disruption does not appear to be a significant problem in F. heteroclitus at the sites in the Chesapeake Bay.