Near-black frogs far outnumber their highlighter-yellow fellows in Chernobyl’s radiation-blasted ecosystems, in a direct example of “evolution in action,” a new study shows. The study, published Aug. 29 in the journal Evolutionary Applications (opens in new tab), found that eastern tree frogs (Hyla orientalis) with more skin-darkening melanin pigment were more likely to survive the 1986 nuclear accident in Ukraine than frogs with lighter skin, leading to populations today that are dominated by darker frogs.
“Radiation can damage the genetic material of living organisms and generate undesirable mutations,” researchers wrote in a post on The Conversation (opens in new tab) about their research. “However, one of the most interesting research topics in Chernobyl is trying to detect if some species are actually adapting to live with radiation. As with other pollutants, radiation could be a very strong selective factor, favoring organisms with mechanisms that increase their survival in areas contaminated with radioactive substances.”
On April 26, 1986, a reactor at the Chernobyl nuclear power plant in Ukraine exploded, spewing radioactive materials across an 18-mile (30 kilometers) radius.
“The Chernobyl accident released approximately 100 times the energy released by the nuclear bombs of Hiroshima and Nagasaki,” Pablo Burraco, the study’s lead author and a biologist with the Doñana Biological Station in Seville, Spain, told Live Science in an email.
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Officials evacuated residents from the contaminated zone following the disaster and established a 1,040 square-mile (2,700 square kilometers) exclusion zone. In the decades since, the abandoned area has become a wildlife refuge. Burraco and his team wanted to understand how the nuclear meltdown drove evolution in the animals living there.
After studying more than 200 male frogs whose habitats were spread across 12 different breeding ponds throughout the radioactive contamination zone, researchers found that “on average, 44% were darker than those outside of Chernobyl,” Burraco said. “We consider the most plausible explanation to [why] frogs within the Chernobyl Exclusion Zone [are changing color] is that the extremely high radiation levels at the moment of the accident selected for frogs with dark skin.”
Why dark skin? It turns out that high melanin levels in frogs’ skin shielded them from radiation.
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