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A study carried out in partnership with the University of Lausanne shows that a hormone plays a key role in the change of status of these insects

Why do ants come out of their anthills? What explains why they travel great distances when they grow up? The answer is given for the first time by a team of Japanese and Lausanne researchers: it is a molecule that is linked to the evolution of their behavior.

An article published today in the American journal Proceedings of the National Academy of Sciences (PNAS) thus demonstrates that a hormone, inotocin, allows young workers to strengthen their shell in order to be able to leave the anthill and change their position. role within the colony.

Inotocin is a neuropeptide, a small protein in the brain that has the same origin as oxytocin. In vertebrates, the latter already has known effects. For women, it is she who stimulates uterine contractions during childbirth, and lactation when breastfeeding the baby.

The research was initiated in 2016 by the Japanese Akiko Koto, who came to do her post-doctorate in Switzerland within Laurent Keller’s team, at the Department of Ecology and Evolution of the Faculty of Biology and Medicine of the University. of Lausanne (Unil). Myrmecologists began by collecting Camponous japonicus and Camponotus fellah from queens imported from Israel and Japan. These ants are large enough to be studied in the laboratory. To determine their age throughout their experiments, they painted a different color on the newborns each month.


They also had to develop their own system for tracking the ants, by implanting a radio frequency microchip (RFID) in them while they were immobilized on ice, in order to follow their movements and thus deduce their behavior. Then we had to quantify inotocin. To do this, the researchers measured the activity of genes associated with its expression.

Akiko Koto returned to Japan with the ants and continued research at the University of Tokyo and the National Institute of Advanced Industrial Science and Technology in Tsukuba. The results are important in the discipline of insect science, entomology. They show that the level of inotocin varies according to the age of the ant.

During the first four months of their existence, the ants studied occupy a role of nurses and remain within the nest to take care of new eggs, larvae and nymphs. Inotocin is then in small quantities in their body, measured the authors.

Protective layer

After a certain age, they become fodder and leave the anthill in search of food. This is when the inotocin level increases, noted Laurent Keller, myrmecologist at Unil, who led the research.

The cuticle, this reinforced shell of ants, is not only a bulwark against the cold or aggressions, it is also a way for them to recognize themselves and identify the members of the same colony. For the Lausanne researcher, who readily calls himself an “ant breeder” when asked about his profession, “it is interesting that a hormone which has a unique origin and which has been maintained in mammals and in insects is at the origin. ‘origin of very different behaviors’. This should open the door to new discoveries about the role of oxytocin in mammals.