When it comes to dealing with industrial pollution, the Atlantic killifish is even tougher than Springfield's iconic three-eyed fish.
This hardy freshwater fish has evolved in the wild to become 8,000 times more resistant to highly toxic pollutants, perhaps within a matter of decades, according to a new study published in the journal Science.
Researchers from the University of Birmingham, UK and University of California, Davis, sequenced complete genomes of nearly 400 Atlantic killifish populations at New Bedford Harbor in Massachusetts, Newark Bay in New Jersey, Bridgeport area in Connecticut, and Elizabeth River in Virginia. Although these sites vary in their levels of pollution, they have all witnessed industrial pollution since the 1950s and contain a nasty cocktail of dioxins, PCBs, heavy metals, hydrocarbons, and other chemicals.
The genetic analysis found these urban-living fish were incredibly well-suited to living in their radically altered habitats, showing none of the expected effects of the industrial pollutants, such as deformities during embryo development (image below).
Even more remarkably, fish from the different regions had developed pollution-resistance through fairly similar genetic changes to their aryl hydrocarbon receptor (AHR) signaling pathway. This pathway helps the fish to metabolize or break down toxins. Since high levels of industrial pollution only become present during the 1950s and 1960s, it suggests that these genetic changes most likely occurred within 60 years or just a few dozen generations.
A healthy killifish embryo mid-development (left) and a killifish embryo showing signs of deformation after being subjected to PCB. Bryan Clark/US EPA
Professor John Colbourne, Chair of Environmental Genomics at the University of Birmingham, explained in a statement that this species is "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."
This species of fish has the highest level of genetic variation of vertebrates, even more than humans. This effectively allows evolution to act at a faster rate than expected as the population can “weed out” the good genes faster.
It might sound promising that an animal can evolve quickly enough to cope with radical changes from, for example, industrial pollution or man-made climate change. However, the study authors were quick to warn that this demonstration of rapid evolution remains somewhat of a freak example.
“Some people will see this as a positive and think, ‘Hey, species can evolve in response to what we’re doing to the environment!’” lead author Andrew Whitehead, of UC Davis' Department of Environmental Toxicology, said in another statement. “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.”