Chernobyl frogs exposed to radiation show no signs of accelerated aging or increased levels of stress hormones

The radiation exposure of the frogs living in Chernobyl has no effect on their age or the rate at which they age. In fact, these two characteristics do not differ between specimens captured in areas with high levels of radiation and those living in control areas without radiation. There were also no differences found in levels of corticosterone, a hormone linked to the response to stress depending on the radiation to which these amphibians are exposed.

These are the main results of research led by the University of Oviedo and the Doñana Biological Station-CSIC, in which international experts collaborated, and which analyzed for the first time the possible long-term effects of radiation on the age and rate of aging of the Chernobyl fauna.

The work was published in the journal Biology letters. Germán Orizaola, professor of zoology at the University of Oviedo, emphasizes that these results suggest that “the radiation levels to which the frogs are currently exposed in Chernobyl would not be sufficient to cause chronic damage to these organisms.”

Developing this type of study, which accurately measures radiation exposure and analyzes long-term biological characteristics such as age and aging rate, “is crucial to carry out a correct assessment of the current impact of the accident on wildlife. The results of “This work highlights the role of the Chernobyl Exclusion Zone as a nature reserve that must be preserved,” adds this researcher.

The authors of the paper recall that almost four decades have passed since the accident in reactor 4 of the Chernobyl nuclear power plant (Ukraine). During this time, radiation levels in the areas originally affected have decreased significantly.

It is estimated that less than 10% of the radiation emitted in the accident remains and some of the most dangerous isotopes, such as iodine, disappeared within a few months of the accident.

Recent studies show that Chernobyl has actually become one of the largest nature reserves in Europe. For this reason, it is essential to accurately assess the extent to which this accident continues to have harmful effects on the environment today.

A work that began in 2016

Germán Orizaola’s team has been working in Chernobyl since 2016 and is studying the state of the animal populations in the region.

Her studies focused on amphibians, particularly the eastern frog (Hyla orientalis). Previous research found that current radiation exposure has no effect on various physiological and morphological parameters related to the health status of this species.

In this work, scientists examined the effects of radiation on the age and rate of aging of these amphibians. This is an important aspect when assessing the long-term effects of radiation exposure as it may reflect the accumulation of damage throughout the animal’s life.

The fieldwork was carried out in collaboration with Pablo Burraco, a researcher at the Doñana Biological Station, in three consecutive campaigns in Ukraine between 2016 and 2018.

In this study, researchers sampled populations of this amphibian along the entire gradient of radioactive contamination present in the region, including from some of the most contaminated areas in the world to areas with no radioactive contamination. In total, they captured more than 200 male Eastern Anthony’s frogs at 14 different locations, which they brought to their field laboratory in the city of Chernobyl, Ukraine.

“For all frogs, we calculated the amount of radiation absorbed based on ambient radiation and the levels of cesium in their muscles and strontium in their bones. This was one of the most accurate assessments of absorbed radiation performed on a vertebrate at Chernobyl,” says Pablo Burraco.

The researchers point out that in amphibians it is possible to calculate the age of an individual by counting the growth lines of their bones that form each year, in the same way that one determines the age of a tree. This work also examined the aging rate of these individuals, using telomere length as a marker.

Telomeres are DNA sequences at the ends of chromosomes that protect genetic material and shorten with each cell division. In addition, levels of the hormone corticosterone in the subjects’ blood were measured as a marker of response to stress.