Rapid Evolution in Hudson River Tomcod
Isaac Wirgin, Ph.D.
New York University School of Medicine
NIEHS Grants P42ES007381, P30ES000260, and R01ES015447
New research findings by NIEHS grantees suggest that Hudson River tomcod have undergone rapid evolution in response to industrial contamination of the river with polychlorinated biphenyls over the last 50 years. Natural selection, the driving process in evolution, usually takes place over thousands of years, but the research team reports that this is the first example in vertebrate animals of such a rapid evolutionary change.
The research team is made up of NIEHS and Superfund Research Program grantees at New York University and the Boston University School of Public Health. They found changes in the gene that codes for the Ah Receptor 2 (AHR2), which is important in mediating toxicity in early life stages. The AHR2 protein in the Hudson River fish is missing two amino acids, which causes a weaker bond between the receptor and PCBs, a necessary step in the metabolism of the compound. The variant is found in about 95 percent of the Hudson River fish and in about 5 percent in tomcod in two smaller streams in Connecticut and on Long Island. The variant can't be found at all in fish further down the Hudson.
Because the Hudson River fish is resistant to the toxic effects of PCBs, they are able to accumulate more of the chemical without becoming sick. However this evolutionary adaptation is not all good news for the ecosystem. Since the fish can bioaccumulate the compound at higher levels, consumption of them by other fish can lead to transfer of PCBs up the food chain.
Citation: Wirgin I, Roy NK, Loftus M, Chambers RC, Franks DG, Hahn ME. Mechanistic Basis of Resistance to PCBs in Atlantic Tomcod from the Hudson River. Science. 2011 Feb 17. [Epub ahead of print]
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