Ever since a couple of colleagues and I foolishly thought we could actually transplant caged killifish in the wilds of New Jersey — a contaminated Newark backwater to be more exact (within a week the fish were gone, cages and all – stolen) I’ve been interested in the incredibly resistant little minnow. Not only can it withstand a flopping around in the trunk of a University car (thankfully no one commented on the slightly damp fishy smelling trunk upon its return) but these fish do just fine in environments that would otherwise be considered highly contaminated with PCBs, dioxins and similar chemicals as well. In the sixteen or so years since our fish were stolen, some really nice work has been done by Diane Nacci and her group at the Atlantic Ecology division of the EPA, and Andrew Whitehead at Louisiana State University whose work confirms not only have killifish evolved resistance to these human-aged chemicals but that in a great example of convergent evolution, distinct populations appear to have evolved a “similarly profound desensitization of aryl-hydrocarbon receptor-mediated transcriptional activation”. For more, see their most recent paper, Common mechanism underlies repeated evolution of extreme tolerance to pollution, published in the Proceedings of the Royal Society B. As to how different populations might similarly evolve write the authors: “The rapid, repeated, heritable and convergent nature of evolved tolerance suggests that ancestral killifish populations harboured genotypes that enabled adaptation to twentieth-century industrial pollutants.”
As we learn more about the evolution of vertebrates, it will be interesting to see if this model holds – and for how many species facing similar environmental degradation as killifish.