Ants sick stay away from children

Ants are posters for eusociality. Every ant has a job, and every ant sticks to its work: fodder forages, workers work, nurse nurse, procreate queen. It has been hypothesized that this strict separation of the ants' society into age groups and tasks could help prevent epidemics, but this hypothesis has never been tested. Eventually, a group of scientists met and discovered how to experiment using 22 colonies of Lasius Niger, the common black ant.

A division of more than just work

The scientists came from various departments of various universities: ecology and evolution, science and technology, biorobotics, intelligent systems and physics of complex systems. They labeled each ant in each colony with what looked like a paper QR code glued to his chest and used video tracking to track individual ants, monitoring all physical contact between them.

As expected, the colony structure inhibited the transmission of pathogens. Colonies were divided into separate connected communities, but the nodes to which they were connected were limited. This organization also protected the most vulnerable members: the queen and young workers.

The whole network aimed not only to limit the transmission of the disease, but also the ants. The people most likely to get an infection are foragers, because the nest is kept scrupulously clean by the workers, who stay inside. Forage ants have fewer connections within the network and are clearly separated from the queen and young nurses.

These observations were made by comparing the network of ant colonies to other types of simulated infection networks, but they were then confirmed with true infections. Scientists have randomly infected 10% of foragers in a colony with the spores of a pathogenic ant, Metarhizium brunneum. (Only 11 of the colonies were infected, 10% of the foragers of the 11 others were exposed to a dummy solution.) After giving the foragers one day to recover from their treatments, the researchers analyzed the burden of pathogens in all the ants of the basin. colony. This has revealed contact networks because the spores are transferred by physical contact between the ants.

Limited contact

Untreated forages ended up with a much higher pathogen load than the queen and young nurses sequestered in their nest. After nine days, more browsers died than ants from any other caste; all the queens were still alive.

Exposure to pathogens and not dummy treatment altered the behavior of ants in a way that further protects the colony. Infected fodder spent more time outdoors, moved away from the colony and did not move much when they entered the nest. The nurses moved the clutch deeper into the nest. We do not know how they knew, but these changes in behavior reduced both the probability of contamination and the number of spores transmitted by touch. They also served to vaccinate the queen by allowing her to expose herself only to a low level of contamination by pathogens.

One of the practical consequences of this finding, that the strict regulation of the caste ants society helps to protect their young and their queens from epidemics, is that if you offer your child one of these toys, colony of ants for Christmas, he The house will live long and will resist epidemics.

Science, 2018. DOI: 10.1126 / science.aat4793 (About DOIs).