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Evolution of Tolerance to PCBs and Susceptibility to a Bacterial Pathogen (Virbrio harveyi) in an Atlantic Killifish Fish (Fundulus heterclitus) from New Bedford (MA, USA) Harbor
Citation:
NACCI, D. E., M. HUBER, D. M. CHAMPLIN, S. JAYARAMAN, S. Cohen, E. Gauger, A. Fong, AND M. Gomez-Chiarri. Evolution of Tolerance to PCBs and Susceptibility to a Bacterial Pathogen (Virbrio harveyi) in an Atlantic Killifish Fish (Fundulus heterclitus) from New Bedford (MA, USA) Harbor. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 157(3):857-864, (2009).
Impact/Purpose:
This manuscript describes experimental studies which contribute to our understanding of the ecological risks associated with chronic contaminant exposures to wildlife populations. Here, we measured intra-specific variation in pathogen susceptibility in wild populations that vary in their exposure and response to contaminants. More generally, this research describes the use of controlled studies to assess the impact of chemical contamination on an important regulator of population dynamics, infectious disease. General impacts from this contribution include improved understanding by managers and scientists of links between human activities, natural dynamics, ecological stressors and ecosystem condition.
Description:
We are studying adaptation in a population of the non-migratory estuarine fish Fundulus heteroclitus (mummichogs) that has evolved tolerance to some of the effects of the toxic pollutants, polychlorinated biphenyls (PCBs) contaminating their residence site, New Bedford (NB), Massachusetts (USA). This evolved tolerance provides protection from early life stage mortalities associated with PCB exposure, but the broader ecological benefits and costs of this adaptation to the persistence of the NB mummchog population are poorly understood. We were specifically concerned about vulnerability to infectious disease in NB mummichogs because PCBs are highly immunosuppressive, and increased disease vulnerability is a potential trade-off of adaptation. To directly compare disease susceptibility of mummichogs from NB and other less contaminated, reference sites, we conducted acute laboratory bacterial challenges using a marine pathogen. Despite potentially immunosuppressive chemical exposures, field-collected NB mummichogs survived bacterial challenges better than those from less contaminated sites. Differences in survival between challenged populations were consistent throughout the reproductive season, and driven by higher survival rates of NB males. An additional study using laboratory-reared fish showed similar survival rates for NB and reference mummichogs. These laboratory studies are inconsistent with hypothesized adaptive trade-offs and suggest that evolved tolerance in NB mummichogs includes mechanisms that minimize the immunosuppressive effects of PCBs, a potentially important contributor to population persistence in the wild.