Evolution has rescued a fish from lethal human pollution by adapting it to cope with toxic chemicals.
Atlantic killifish live in four US east coast estuaries that contain high levels of industrial pollutants
Scientists have found the fish have become up to 8,000 times more resistant to the poisons than other species, allowing them to survive in an environment that would kill most species.
The killifish's secret is a higher level of genetic variation than any other vertebrate, including humans, say the researchers.
The scientists mapped the genomes, or genetic codes, of almost 400 Atlantic killifish from polluted and non-polluted sites in Massachusetts, New Jersey, Connecticut and Virginia.
Since the 1950s and 1960s, the affected sites have been polluted by a complex mixture of chemicals.
The findings, published in the journal Science, suggest that surviving pollution involved a particular adaptation common to them all.
Lead scientist Dr Andrew Whitehead, from the University of California at Davis, said: "If we know the kinds of genes that can confer sensitivity in another vertebrate animal like us, perhaps we can understand how different humans, with their own mutations in these important genes, might react to these chemicals."