DNA diversity helps some fish tolerate toxic levels of pollution

London, Dec 10 (IANS) Some groups killifish are up to 8,000 times more resistant than others to highly toxic industrial pollutants such as dioxins, heavy metals and hydrocarbons, thanks to their high levels of genetic variation, a study says.

"The Atlantic killifish seem particularly well-positioned to evolve the necessary adaptations to survive in radically altered habitats, because of their large population sizes and the relatively high level of DNA diversity seen in their populations," said one of the researchers John Colbourne, Professor at University of Birmingham in Britain.

The researchers wanted to explore the genetic mechanism responsible for evolutionary adaptation to toxic pollution observed in wild Atlantic killifish populations.

The Atlantic killifish is renowned for its ability to tolerate large fluctuations in temperature, salinity and oxygen levels.

However, its rapid adaptation to the normally lethal levels of toxic pollution found in some urban estuaries in the US is unusual, even for such a hardy species.

The team analysed the genomes of four wild populations of pollution-tolerant killifish compared with four non-tolerant populations, to identify the mechanism behind this adaptation.

"This report highlights the complexity of the processes involved in the adaptation of wild fish to lethal levels of environmental pollution," Colbourne said.

"It also demonstrates how the DNA of populations that differ in their susceptibility to pollutants can reveal 'signatures' of the adverse effects of chemicals in the environment," Colbourne noted.

The researchers warned that these findings -- published today in the journal Science -- should not be used to justify the harm caused by human pollution of the natural environment.

"Unfortunately, most species we care about preserving probably can't adapt to these rapid changes because they don't have the high levels of genetic variation that allow them to evolve quickly," lead author Andrew Whitehead, Associate Professor at University of California, Davis in the US.