Evolution has come to the rescue of some urban fish that live in lethal and human-altered environments. In a new study, researchers reported of a fish that has evolved to be 8,000 times more resilient to toxic waste compared with normal fish.

Atlantic Killifish

The Atlantic killifish that lives in the heavily polluted East Coast estuaries such as the Elizabeth River in Virginia and the Newark Bay in New Jersey turned out to be very resilient to environmental change. The fish has evolved to adapt to the amount of highly toxic industrial pollutants that would normally kill them.

The small striped fish is not commercially valuable but it is a favorite among aquarium owners because of its small size and beautiful colors. Ecologists also use it as an indicator species acting like an aquatic canary in polluted environments.

How The Atlantic Killifish Survives In Highly Polluted Environments

Researchers attributed the resilience of the killifish to high levels of genetic variation that scientists have so far found to be higher than those of other vertebrates including humans.

Evolution tends to act faster with more genetic diversity which explains why insects and weeds can easily evolve to resist the pesticides meant to eliminate them and why disease-causing bacteria and viruses can evolve fast to resist the drugs developed to destroy them.

For the study published in the journal Science on Dec. 9, researchers sequenced the genomes of nearly 400 killifish from polluted and non-polluted sites. The polluted sites have been contaminated by a mixture of industrial plants which include heavy metals, dioxins, hydrocarbons and other chemicals since the 1950's and the 1960's.

Genetic analysis revealed that the genetic diversity of the killifish makes it unusually well-positioned to adapt and survive in habitats that have been radically changed. The researchers conclude that the fish already has the genetic variation needed for them to adapt even before the habitats they live in became polluted.

"High genetic diversity in killifish seems to allow selection to act on existing variation, driving rapid adaptation to selective forces such as pollution," the researchers wrote in their study.

Evolution Not Always The Answer To Environmental Changes

Study author Andrew Whitehead, from the University of California Davis Department of Environmental Toxicology, however, said that this does not mean species would just evolve to respond to human-caused changes to the 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," Whitehead said.

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