A study carried out since 2017 in the Chernobyl exclusion zone (Ukraine) by the researcher at the University of Oviedo German Orizaola reveals that frogs in that area have darker pigmentation than those in nearby areas. Dark coloration, associated with a higher concentration of melanin, could reduce the damage caused by radiation to living organisms, dissipating part of this radiation or reducing the action of free radicals.
This study constitutes one of the first suggestions of the existence of adaptive responses to radiation in vertebrates. The work, confirmed by Paulo Burracocurrently researcher of Doñana Biological Stationhas just been published in the magazine evolutionary applicationsmaximum impact in your area of expertise.
Orizaola, a researcher at the Department of Biology of Organisms and Systems at the University of Oviedo, recalls that the accident in reactor number four at the Chernobyl nuclear power plant (Ukraine) on April 26, 1986 generated the largest release of radioactive substances in the history of the environment.
“The initial impact of the accident on the nature of the area and on the human population was severe,” he says. However, more than three decades have passed since the accident and the area has become a nature reserve. refuge for species such as the wolf, the lynx or the brown bear. “Determining the long-term impact of an accident like Chernobyl on natural ecosystems has become a scientific and management priority,” he adds.
Chornobyl graphic frogs. / University of Oviedo
One of the aspects that currently arouses greater interest in the scientific community is the possibility that Chernobyl is generating processes of radiation adaptation. The present study examined the coloration of 189 breeding males of the eastern San Antonio frog (2017-2019) between 2017-2019.Hyla orientalis), inside and outside the Chernobyl Exclusion Zone (Ukraine). This species, distributed in Eastern Europe and around the Black Sea, has a typical bright green coloration.
The work was carried out in twelve locations distributed along a wide gradient of radioactive contamination, from locations with levels more than one hundred times higher than normal, to four locations outside the Exclusion Zone and with baseline levels of radiation. In addition to the coloring of the back, the dose of radiation absorbed by each frogas well as their levels of oxidative stress, which may be associated with both radiation exposure and melanin production.
The darker the closer high radiation zones
The results showed that the coloration of the examined individuals is significantly darker inside the Chernobyl Exclusion Zone than in the external locations until completely black individuals are found. Specifically, a direct relationship was detected between the color of the back and the distance to areas of high radiation at the time of the accident. The darkest individuals were found in or near the areas that experienced the highest levels of radiation in 1986.
Team fieldwork in Chornobyl. / University of Oviedo
Virtually all frogs caught outside the Exclusion Zone showed the bright green color characteristic of the species. On the other hand, no relationship was found between the color of the frogs and the radiation dose currently absorbed by these individuals. No increased levels of oxidative stress were detected in the darker frogs or those with higher levels of absorbed radiation.
These results suggest that differences in coloration are not due to current radiation exposure and point to the effect of historical exposure on these populations. This study suggests that the dark coloration of the Chernobyl frogs may be a consequence of a natural selection process generated by the initial exposure to very high levels of radiation.
Individuals with darker coloring, that is, with greater melanin levels, would have suffered less impact from the radiation released by the accident. This greater protection would have increased its frequency in the population, up to the levels currently detected.
“The present study constitutes a breakthrough in research work on the ecology of the Chernobyl Exclusion Zone. Furthermore, it opens up new lines of research to examine the role that melanin can play in radiation protection, with potential applications ranging from nuclear waste management to space exploration,” concludes Orizaola.
The work, carried out by researcher Germán Orizaola from the University of Oviedo, opens new lines on the protective role of melanin against radiation, with potential applications ranging from nuclear waste management to space exploration.
German Orizaola. / University of Oviedo
Reference:
Burraco, Pablo & Orizaola, Germán 2022. Ionizing radiation and melanism in Chornobyl tree frogs. evolutionary applications.