Frogs exposed to radiation show no signs of accelerated aging

The frogs residing in the Chernobyl Exclusion Zone appear remarkably unaffected by radiation when it comes to their age and rate of aging.

A recent study shows no significant differences between frogs living in high-radiation areas and those from non-irradiated control zones regarding these two aging traits. 

Additionally, corticosterone levels – a hormone related to stress response – are consistent across frogs regardless of the radiation levels they’re exposed to.

These findings, from a study led by the University of Oviedo and the Doñana Biological Station-CSIC, mark the first analysis on the long-term effects of Chernobyl’s radiation on the age and aging rate of local wildlife. 

According to Germán Orizaola, a zoology professor at the University of Oviedo, “the levels of radiation currently experienced by frogs in Chernobyl would not be sufficient to cause chronic damage to these organisms.”

Chernobyl as a potential wildlife refuge

This study highlights the need for comprehensive analysis of radiation’s long-term effects on biological traits like age and aging rate to accurately assess the current environmental impact of the Chernobyl disaster. 

Orizaola notes that the results support the idea that Chernobyl now serves as a refuge for wildlife that should be protected.

Nearly 40 years have passed since the 1986 meltdown at Chernobyl’s reactor 4, during which radiation levels have substantially declined in the initially affected zones. 

Experts estimate that less than 10% of the original radiation remains. Isotopes such as iodine, which posed significant danger after the accident, disappeared within months. 

This sharp reduction in radiation has allowed the area to become one of Europe’s largest natural reserves, prompting scientists to carefully examine its lingering impact on the local environment.

Long-term impacts of radiation on aging

Led by Orizaola, the research team began studying Chernobyl’s wildlife in 2016, with a focus on animal populations in the exclusion zone, especially amphibians like the eastern tree frog (Hyla orientalis). 

Past research by this group revealed no detectable impacts from current radiation levels on various health-related physiological and morphological parameters in this species.

In the current study, scientists extended their focus to the age and aging rate of these frogs, hoping to detect any cumulative radiation damage over the animals’ lifespans. 

Understanding the long-term impact of radiation on aging is crucial, as it reflects how radiation exposure might accumulate and affect organisms over time. 

The fieldwork, conducted with Pablo Burraco of the Doñana Biological Station, spanned three research trips to Ukraine between 2016 and 2018.

Measuring radiation exposure in frogs

The researchers sampled frog populations across the gradient of radiation exposure present in the area, including locations with some of the highest radioactive contamination in the world and areas with no contamination. 

They captured over 200 male frogs from 14 different sites and transported them to their field laboratory in Chernobyl city. 

“In all the frogs, we calculated the level of radiation absorbed based on the environmental radiation and the cesium content in their muscles and strontium in their bones,” noted Burraco. 

“This has been one of the most precise assessments of absorbed radiation carried out on a vertebrate in Chernobyl.”

Calculating frog age using growth lines

The researchers used growth lines in frog bones, much like counting tree rings, to determine each frog’s age. To analyze aging rates, they measured the frogs’ telomere lengths. 

Telomeres, DNA sequences located at chromosome ends, protect genetic material and shorten with each cell division – a process associated with aging. Corticosterone levels were also measured to assess each frog’s stress response, providing another data point in the research.

This study’s findings suggest that frogs in Chernobyl’s exclusion zone have adapted to the radiation levels present without significant effects on their aging processes. 

The research contributes valuable knowledge to ongoing research into Chernobyl’s wildlife, reinforcing the importance of the exclusion zone as a wildlife refuge and emphasizing the resilience of some species in radiation-exposed environments.

The study is published in the journal Biology Letters.

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