The Colorado potato beetle is known for being a "notorious pest," a kind of overpowering genius.
In the 1860s, the modern pesticide era started when farmers started to kill these beetles by spraying them using a paint color known as "Paris Green" with copper arsenate content.
A Phys.org article reported that these insects soon beat that poison, as well as "lead arsenate, mercury DDT, and dieldrin," and more than 50 other pesticides.
Also, according to the same report, initially, with any new chemical, many beetles get killed, "but none of (the pesticides) last long." The beetles usually develop resistance within a couple of years and continue to merrily chomp their way through massive acres of potatoes in farms and gardens globally.
Scientists are said to have a poor understanding of how these Colorado potato beetles do their trick. Present evolutionary theory, with a focus on DNA, has fallen short of explaining a swift development of resistance to pesticides.
As the beetle exhibits a lot of genetic differences, perhaps, new DNA mutations do not appear often enough to enable them to develop resistance to many types of pesticides -- speedily and repeatedly.
First-of-Its-Kind Study
Now, a first-of-its-kind study dramatically moves closer to an explanation. A research team led by University of Vermont's Professor Yolanda Chen presents even "small doses of neonicotinoid pesticide, imidacloprid," can change how the beetle is managing its DNA.
To ward off the pesticides, the new study proposes, the beetle may not need to alter its original genetic code. Rather, the team discovered that beetles react by changing their DNA's regulation, turning specific genes on or off in a process also known as "DNA methylation."
The so-called "epigenetic changes," explained Chen, enable beetles to swiftly ramp up biological protection mechanisms, probably putting into overdrive already-available genes that enable the beetle to endure a great range of poisons found in potato plants.
A faster excretion rate or a flush of enzymes may allow the insect to stymie every new pesticide with similar ancient biochemical mechanisms that it employs to overcome natural plant resistances, instead of depending on the heavy evolutionary process of random mutations showing up in key genes. This would gradually lead a pesticide to become less efficient.
Surprising Finding
Most essential of all, this new research shows that these alterations, stimulated by even small doses of the pesticide, can be transferred to offspring through at least two generations.
Chen also said they found similar "DNA methylation patterns in the grandkid generations," which was surprising as they were not exposed to the insecticide.
In many other species of insects, pesticide exposure has been presented to alter DNA methylation. And specific epigenetic alterations have been observed to be transferred to future generations of insect species that asexually reproduce, like the tiny crustacean Daphnia magna.
It has long been assumed, though, said Kristian Brevik, the lead author of this study that "epigenetics resets during sexual reproduction."
However, such alterations could be transferred through multiple rounds of sexual reproduction to future generations of insects, and this finding, Brevik added, is something new.
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