Research shows that young ants, once they become sick, emit a distinctive scent that signals workers to remove them from the colony, preventing the spread of infection. Interestingly, queens do not use this self-sacrificing mechanism.
Many animal species hide their disease for social reasons. Even humans often risk infecting others just to continue their routine, whether at work or in a coffee shop. But ant colonies function as a “superorganism” that acts for the survival of all, similar to the way infected cells in our bodies send out the “find me and destroy me” signal, reports a team of researchers from Austria.
"Ants live in ideal conditions for the spread of diseases, because thousands of them are moving over each other all the time," explains Erika Doson, a behavioral ecologist at the Austrian Institute of Science and Technology and the lead author of the study.
When adult worker ants become infected with a disease that could threaten the colony, they leave their nests to die in isolation. But young ants, still inside, cannot practice this kind of social distancing.
Researchers have discovered that when these terminal larvae become sick, a chemical change occurs that produces a specific odor. Worker ants gather, open the protective cocoon, create holes, and inject venom inside, Doson explains.
This poison acts as a disinfectant, while also killing the pathogen that threatens the colony, the Telegraph reports.
In the new study, scientists aimed to understand exactly what this mechanism is and how the signal that can be translated as: "Hey, come and kill me" works.
They first isolated the scent of sick ants of the species lasius neglectus, and when they applied this scent to healthy larvae in the lab, the worker ants destroyed them as well.
The team then conducted an experiment that showed that the diseased larvae only produce this scent when the workers are nearby, which suggests that they are releasing the scent intentionally, as a signal for elimination.
"Even though it's a form of sacrifice, it's in their evolutionary interest because it ensures their genes are passed on to the next generation," explains Dawson. But one member of the colony doesn't use this self-sacrificing strategy.
When queens become infected, they they do not emit an aromatic signal, the team has discovered, raising the question: "Are they cheating the system?"
However, researchers found that queen larvae have much stronger immune system than those of workers, therefore they manage to fight the infection and, precisely for this reason, it is thought that they do not send the signal of self-sacrifice.
Doson adds that he hopes future studies will reveal whether queens are also sacrificed in cases where it becomes clear that the infection is irreversible.
The study is published in the journal Nature Communications /Telegraph/
