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A team of researchers in France are building on fundamental experimental research undertaken in the Ukrainian Chornobyl exclusion zone with a new project in the Japanese Fukushima Prefecture to further our understanding of what it means for animals to live and reproduce in radioactive environments.

Ms. Léa Dasque, a final year Ph.D. student at the LECO laboratory (Laboratory of Ecology and Ecotoxicology of Radionuclides) under the French Nuclear Safety and Radiation Protection Authority (ASNR), supervised by project lead Dr. Olivier Armant, also of LECO and ASNR, aims to disentangle the complex web of biological interactions that shape how wildlife respond to radiological stress.

"We aim to answer a simple question: What is the current evolutionary and ecological status of wildlife populations residing in radio-contaminated areas, and how are they likely to change over time?" says Ms. Dasque.

Most recently, Ms. Dasque and her colleagues have been investigating the reproductive traits of Japanese tree frogs (Dryophytes leopardus) living in the Fukushima Prefecture in Japan, site of the 2011 Fukushima Daiichi Nuclear Power Plant disaster.

Reproductive success is life's primary driving force, but it is one of the biological processes most vulnerable to the harmful effects of ionizing radiation, which makes it a critically important piece of the puzzle. "Ionizing radiation can disrupt endocrine function, gametogenesis, and mating behaviors, all of which may impair fecundity and offspring viability," says Ms. Dasque.

"For instance, our research in Chornobyl documented reduced body condition index and small population sizes in highly contaminated zones," says Dr. Armant. "In Fukushima, we aim to find out if similar effects can be also observed after another major accident, and if effects and reproduction are at the root of such effects observed at the population level."

To carry out their investigations, Ms. Dasque and Dr. Armant use a wide array of techniques and technologies that take place both in the field, namely Chornobyl and Fukushima, and under controlled laboratory studies back in France.

"At the molecular level, we utilize genomics, transcriptomics, and proteomics to identify cellular responses to ionizing radiation exposure and study population-level effects," says Dr. Armant. At the organismal level, the team are looking at the body condition, energy reserves and sexual characteristics.

In their most recent work on the reproductive qualities of Fukushima tree frogs, they also assessed the male frog's sperm, energy metabolism, and calling characteristics. "These are extremely costly to produce and closely linked to female attraction," says Ms. Dasque.

A key discovery from the team's work in Chornobyl is that amphibian populations in the exclusion zone's most contaminated areas struggle with poor genetic diversity compared to other populations, even decades after the accident. Together with declining body conditions, this questions the long-term viability of these populations.

Although analysis of the Fukushima frog project is still ongoing, preliminary results suggest that frogs living in radiocontaminated areas are subjected to disruption of genetic pathways associated with sperm motility—potentially altering their reproductive success. "Further data on sperm motility are currently being processed to determine whether this parameter, along with male calling behavior, may be affected by radiocontamination," says Ms. Dasque.

In the lab, the team are also working on a project using zebrafish (Danio rerio), which has revealed that chronic radiation exposure impairs neuromuscular development with consequences for motility, as well as reduces sociability.

It's not just vertebrates that the team are interested in, as they are also currently working in collaboration with the CNRS (French National Center for Scientific Research) to develop a methodology for measuring the cognitive performance of wild pollinators living in Fukushima. "Cognition in pollinators, encompassing learning, memory, and spatial navigation, is essential for efficient foraging and colony functioning," says Dr. Armant. "Our initial data indicates a decline in cognitive performance correlated with the radiation exposure which might influence pollinator behavior and survival."

"Combined exposures—such as radiation plus heat stress—have the potential to produce synergistic effects not predictable from single-stressor models," says Dr. Armant. "This calls for an evolution in how we assess environmental risk: one that embraces ecological realism, evolutionary dynamics, and long-term monitoring."

This project demonstrates how the impacts on reproductive success are critical to the long-term survival of radiocontaminated populations. "Without considering factors such as genetic diversity, migration patterns, and life-history traits, we risk underestimating the true impact of chronic contamination on biodiversity and ecosystem resilience," says Ms. Dasque.

This research is being presented at the in Antwerp, Belgium on the 11th July 2025.