The Atlantic killfish evolved to be resistant to pollution.

Atlantic killfish. Photo: Public Domain

Atlantic killifish are small fish found along the East Coast, especially in estuaries where they often face high pollution levels. You’d be forgiven for not having heard of them, since they don’t have any commercial value, but they do form an important part of food webs and are eaten by a wide variety of other fish.

What’s special about them is that a recent study has found that Atlantic killifish living in New Bedford Harbor, Newark Bay, Bridgeport, Connecticut, and the Elizabeth River are 8,000 times more resistant to highly toxic industrial pollutants, which would normally be expected to kill them.

These areas have been heavily polluted since the 1950s and 1960s, so the fish have had time to adapt, but the killfish seems to be the only species that has. This is because there’s a huge amount of genetic diversity among Atlantic killifish, which allows them to adapt more quickly than other vertebrate species.

“Some people will see this as a positive and think, ‘Hey, species can evolve in response to what we’re doing to the environment!’” says study lead author Andrew Whitehead of UC Davis. “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.”

So while it’s a good thing that the Atlantic killfish has adapted in this way, because of their importance to food webs, it doesn’t mean fish in general can adapt to pollution in this way.

We can, however, learn from the Atlantic killifish. It might even be possible for scientists to extrapolate lessons learned from the killfish to other species of vertebrates.

The same study that learned how resistant these little fish have become to pollution has also narrowed down the parts of their genome responsible for that resistance. With that information in hand, we might be able to figure out what causes chemical sensitivity in humans and other vertebrates. This could lead to technology or medications that would block some of that sensitivity in order to make it easier for other species to survive while we work on keeping pollutants out of the environment in the first place.