Ants survive massive doses of X-rays: a Namur scientific experiment to quantify their radioresistance

They're all around us, and have fascinated us for centuries. As children, we lean over them to watch them move between our fingers in our gardens, which become jungles. As adults, they still fascinate us, thwarting the traps we try to set for them in our kitchens, which they always invade where we least expect them.

They are ants, and more specifically the species Lasius niger, which we frequently find in our gardens.

"I was leaving my house one summer day in 2022 when I realized that a discreet but very real phenomenon was taking place in front of my house: the streets of my Namur neighborhood were invaded by young queen and male ants taking off for their unique nuptial flight. This flight is at the origin of the fertilization of the queens, which, once back on earth, start a colony in a cavity, our walls or even our rubbish", recounts Boris Hespeels, a researcher at the Unité de Recherche en Biologie Environnementale et Evolutive (URBE) at UNamur. After collecting around a hundred individuals, the scientist, who also conducts research into the resistance of other living organisms in extreme environments (rotifers - read our article on this subject), returned to his laboratory with the desire to test a popular culture myth: the extreme resistance of these insects in particular to numerous stresses, such as radiation from nuclear bombs.

In the enthusiasm, a collaboration was formed between researchers from the Departments of Biology and Physics. After some brainstorming, an experimental protocol was devised, leading to a concrete, fully supervised and secure experiment (read elsewhere). Today, four UNamur researchers have published the first study to assess the radioresistance of black ants Lasius niger to massive doses of X-rays. Published in the Belgian scientific journal Belgian Journal of Zoology, it reveals how Lasius niger manages to survive more than 11 weeks after receiving massive doses of X-rays (up to 250 Gray(Gy), whereas human cells generally do not resist beyond 10 Gy). However, the researchers also discovered that from a certain dose of irradiation onwards, the females were rendered sterile, despite surviving.

The results were compared with the few data previously obtained from radiation experiments in the fight against invasive ant species. While the mechanisms of protection and damage repair in ants are still unknown, this study confirms that ants' radioresistance, as well as their subterranean lifestyle, give them a resistant species status in the event of radioactive fallout.

This experiment was carried out by the researchers using an approach independent of any project or funding, thus experimenting with an approach known as Crash-and-Learn ("Failure and Learning"). This work demonstrates the possibilities opened up by carrying out scientific projects outside pre-established frameworks, leaving plenty of room for spontaneous collaboration and the uninterested pleasure of doing research. This approach, which complements the traditional routes linked to funding and guidelines defined sometimes years before the project is carried out, questions the meaning and practice of the researcher's craft.

The conduct of this experiment in no way precludes the researchers' sensitivity to the preservation of biodiversity and respect for living things. No harm was done to the local ecosystem or to animal and human populations. The ants used in this study were irradiated under strictly secure laboratory conditions, with no risk of contamination or dissemination in the wild. The species used, Lasius niger, is a common one, and experimental conditions were strictly limited to the laboratory. In line with the principles of the 3Rs (Reduce, Replace, Refine), the number of exposed individuals was reduced to the strict minimum necessary to guarantee reliable scientific results. In addition, ant stress was limited as much as possible throughout the experiment, which required the use of live individuals.