You are here:
EFFECTS OF A HIGHLY-CONTAMINATED URBAN HARBOR ON AN ESTUARINE FISH SPECIES: NEUTRAL MARKERS OF POPULATION GENETIC STRUCTURE
Citation:
McMillan, A., S. A. Roark, S Christ, M Bagley, AND D E. Nacci. EFFECTS OF A HIGHLY-CONTAMINATED URBAN HARBOR ON AN ESTUARINE FISH SPECIES: NEUTRAL MARKERS OF POPULATION GENETIC STRUCTURE. Presented at Society of Environmental Toxicology and Chemistry Annual Meeting, Baltimore, MD, November 11-15, 2001.
Description:
Fundulus heteroclitus populations indigenous to certain highly contaminated sites demonstrate an inherited tolerance to the toxic effects of local chemical contaminants. Our initial studies examining populations of F. heterclitus indigenous to a PCB-contaminated Superfund site at New Bedford Harbor (NBH), MA, USA, focused on adaptive phenotypic changes. Specifically, F. heteroclitus from NBH survive laboratory challenges to lethal concentrations of dioxin-like PCBs that act through the aryl hydrocarbon receptor (AHR). In addition, these fish are relatively resistant to laboratory bacterial challenges. We are investigating genetic changes associated with adaptation to severe and diverse environmental stressors (see also, McMillan et al., this session) by examining patterns of DNA substitution and genotypic composition at loci of known immunogenetic or xenotoxic metabolic function in these fish. Specifically, NBH F. heteroclitus show altered immunogenetic variation at an MHC Class II DB antigen-binding locus in comparison to healthy populations of fish outside NBH. Amino acid substitutions unique to NBH F. heteroclitus are clustered in the alpha helix region of the receptor where changes are thought to occur more frequently due to recombination rather than point substitutions. Thus, the mechanism of genetic change as well as the resulting genotypic
composition may vary between healthy and heavily-stressed populations. Substitution patterns at silent and replacement sites are also examined in a portion of AHRl to determine whether a previously reported genetic difference between NBH and a reference population (Hahn et al. 2000) is associated with PCB tolerance. While alterations to the xenobiotic response pathway almost certainly reflect the direct force of chemical exposures as selective agents,
immunogenetic alteration may be a reflection of PCB exposure or an indirect result of adaptation to unusual suites of pathogens found in NBH fish. Discussion will focus on effects of anthropogenic stressors on genetic variation at selected loci in wild populations, as well as the utility of selected population genetic markers in ecological assessments.