Chernobyl frogs adapting to radiation

[rogue06]

Holy Peppered Moth Batman!



36 years after the disaster at the nuclear power plant at Chernobyl researchers have discovered that as tree frogs are staging a come back, the closer they lived to areas with historically high radiation levels, the darker their coloring has become.

The researchers from Sweden's Uppsala University said that that, "on average, tree frogs inhabiting the Chornobyl Exclusion Zone were remarkably darker."

Moreover, it appears that the frog coloring correlates to an area’s historic radiation levels, not its current radiation level.

They conclude that the reason why is that melanin -- the pigment that makes organisms darker -- also offers protection from ultraviolet radiation by absorbing and dissipating some of its energy.

Source: Chernobyl radiation set off black frog surge while green frogs 'croaked.' Evolution explains why

The 'protective role of pigmentation' is what's at play

Collage Maker-04-Oct-2022-05.38-PM.jpg
A colored gradient shows how Eastern tree frogs in Chernobyl have adapted to radiation by evolving to have darker skin.

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 Doņana Biological Station in Seville, Spain, told Live Science in an email.

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.

"Melanin is known to protect against radiation because it can mechanically avoid the production of free radicals caused by the direct impact of the radioactive particles on cells," Burraco said. "Radiation can induce oxidative stress and damage essential structures for life such as the membrane of cells or even DNA."

Cells in the lighter frogs were bombarded with higher levels of damaging radiation, which killed them off at higher rates than their darker counterparts. After the blast, dark frogs had a higher likelihood of surviving, the study concluded.

Researchers also looked for potential negative effects of excess melanin on the post-Chernobyl dark frogs. They found that like in other species, including certain types of fungi, having darker pigmented skin didn't harm the overall health of the amphibians and actually helped ionize radiation, which prevents ionized molecules from getting into cells and damaging them.

"The production of melanin can be metabolically costly, this has been described, for example, in several bird species," Burraco said. "However, in frogs, the main melanin pigment is called eumelanin and its production seems not to incur in physiological costs."


Source

© Copyright Original Source

The abstract from the paper, Ionizing radiation and melanism in Chornobyl tree frogs can be read below, or the entire paper by clicking the hyperlink.

Abstract

Human actions are altering ecosystems worldwide. Among human-released pollutants, ionizing radiation arises as a rare but potentially devastating threat to natural systems. The Chornobyl accident (1986) represents the largest release of radioactive material to the environment. Our aim was to examine how exposure to radiation from the Chornobyl accident influences dorsal skin coloration of Eastern tree frog (Hyla orientalis) males sampled across a wide gradient of radioactive contamination in northern Ukraine. We assessed the relationship between skin frog coloration (which can act as a protective mechanism against ionizing radiation), radiation conditions and oxidative stress levels. Skin coloration was darker in localities closest to areas with high radiation levels at the time of the accident, whereas current radiation levels seemed not to influence skin coloration in Chornobyl tree frogs. Tree frogs living within the Chornobyl Exclusion Zone had a remarkably darker dorsal skin coloration than frogs from outside the Zone. The maintenance of dark skin coloration was not linked to physiological costs in terms of frog body condition or oxidative status, and we did not detect short-term changes in frog coloration. Dark coloration is known to protect against different sources of radiation by neutralizing free radicals and reducing DNA damage, and, particularly melanin pigmentation has been proposed as a buffering mechanism against ionizing radiation. Our results suggest that exposure to high levels of ionizing radiation, likely at the time of the accident, may have been selected for darker coloration in Chornobyl tree frogs. Further studies are needed to determine the underlying mechanisms and evolutionary consequences of the patterns found here.

[Sparko]

Soon they will figure out they used to be beavers or something.

[rogue06]

Soon they will figure out they used to be beavers or something.

More likely that they evolved from the mangiest of pirates.

[Ronson]

I wonder how that will play out in the future. If the green pigmentation is camouflage against predators, the darker skin should make them easier to spot. Of course, this assumes there are many predators left in the area after it was radiated.

[Littlejoe]

TMNT.PNGIt's TRUE!

[rogue06]

I wonder how that will play out in the future. If the green pigmentation is camouflage against predators, the darker skin should make them easier to spot. Of course, this assumes there are many predators left in the area after it was radiated.

Given they describe the region as having turned into a wildlife refuge I would assume predators are there as well. Right now it would seem that the defense against radiation outweighed the disadvantage of the darker color.

The dark skin will provide less and less of a benefit as radiation decreases meaning eventually the darker skin will become more detrimental than beneficial