How evolution has rescued this fish from lethal human pollution
Evolution has rescued a fish from lethal human pollution by adapting it to cope with the toxic chemicals.
Atlantic killifish live in four US east coast estuaries that contain high levels of industrial pollutants.
Scientists have discovered that 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.
Evolution acts more quickly in species with greater genetic diversity, which is why weeds and microbes rapidly become resistant to herbicides and antibiotics.
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 dioxins, heavy metals, hydrocarbons and other chemicals.
At the genetic level, the pollutant-tolerant populations evolved in similar ways, the study showed. 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, US, 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."
George Gilchrist, from the US National Science Foundation's Division of Environmental Biology, which co-funded the research, said: "This study shows that different populations of Atlantic killifish exposed to toxic pollution evolve tolerance to that pollution through changes in one molecular pathway.
"This pathway may play a similar role in many animals exposed to pollutants, with slightly different adaptations in response to different toxicants."