Insecticide-resistant mosquitos threaten to spread disease to new populations. Antibiotic-resistant bacteria can evolve into “super bugs.” Now, a tiny shrimp-like creature may be evolving a resistance to pesticides – and that’s a cause for concern among biologists and environmental scientists.
Helen Poynton, assistant professor of molecular ecotoxicology in the School for the Environment at UMass Boston, is the co-author of a new article in the Proceedings of the National Academy of Sciences that discusses how several populations of Hyalella azteca, a type of aquatic crustacean, have developed a pesticide resistance.
If you’re a scientist trying to figure out if a stream is polluted, you might go looking for H. azteca. These crustaceans are notoriously sensitive to pesticides. If the stream is full of H. azteca, the thinking goes, that’s one good sign that the site is relatively pollution-free. In 2009, Donald Weston of UC Berkeley found large numbers of H. azteca in a stream that he knew to be polluted with pesticides. Weston began working with Poynton, as well as colleagues from the University of Oklahoma and Southern Illinois University, to study several streams where pesticide levels are high, but H. azteca seemed to thrive. Back in the lab, the animals showed no signs of ill health after exposure to pesticides.
Using DNA sequencing technology, the team was able to show that the pesticide-resistant animals had developed mutations in a particular gene (the voltage-gated sodium channel), and these mutations made the pesticides ineffective at killing them. Interestingly, the mutations are identical to mutations found in insect pests that are resistant to insecticides. This suggested to the research team that nature chooses common pathways for evolution to occur.
We normally think of evolution as a natural process that can take millions of years. But some species are evolving in response to human impacts on the environment.
“It’s not a good thing if we’re putting enough pollution into the environment that we’re causing evolution to occur,” says Poynton.
What’s more, Poynton says that if the pesticide-resistant animals are the only organisms that survive to reproduce in a given population, genetic diversity in the next generation will be smaller.
“We might start seeing detrimental mutations in the next generation. The animals might be less able to survive new environmental stressors,” Poynton says.
The biggest question still remains unanswered: If Hyalella azteca is evolving a resistance to pesticides, what other species might be evolving at the same time? According to Poynton, “That’s a question that’s worth further study.”