Ant pupae have been found to exhibit a remarkable behavior that contributes to the health of their colonies, according to a study conducted by researchers at the Institute of Science and Technology Austria (ISTA). When infected with an incurable disease, these pupae release a specific scent that prompts worker ants to take drastic action, ultimately leading to their own demise for the benefit of the colony.
In a social species like ants, sick individuals typically distance themselves from the group. However, ant pupae, which cannot move, have developed a unique mechanism to address their plight. The study reveals that infected pupae emit a volatile chemical detectable only from outside their cocoons. This scent signals worker ants to investigate. Once they detect the odor, the workers respond by unpacking the cocoon and biting it to create small openings in the pupae’s body.
Following this, the worker ants apply formic acid, an antimicrobial substance that they produce, to disinfect the infected pupae. While this process effectively eliminates any traces of infection, it also results in the death of the pupae. As Erika Dawson, the study’s lead author, explains, “What appears to be self-sacrifice at first glance is, in fact, also beneficial to the signaler: it safeguards its nestmates, with whom it shares many genes.” By alerting the colony to their infection, these terminally ill ants help maintain the health of the group and ensure the continuation of their genetic lineage.
Implications for Ant Colony Functioning
This research supports the concept of ant colonies functioning as a superorganism, where individual ants act similarly to cells within a body. The worker ants performing the disinfection process are likened to immune cells that respond to diseased cells through chemical signals. This phenomenon is known in immunology as the “find-me-and-eat-me signal.”
To further investigate their findings, the ISTA researchers, in collaboration with Thomas Schmitt from the University of Würzburg, experimented with scent molecules from infected pupae. They transferred these molecules to healthy pupae, which prompted worker ants to destroy the ones that emitted the disease-scent. Interestingly, the researchers noted that only the pupae of worker ants released the find-me-and-eat-me scent. Queen ant pupae did not emit this signal, likely due to their stronger immune systems that enable them to better withstand infections.
Connections to Previous Findings
This latest study correlates with earlier research indicating that ants infected with fungal spores exhibit social distancing behaviors. Infected ants were seen isolating themselves, even constructing separate entrances and tunnels in their nests. Additionally, it has long been documented that ants nearing the end of their lives engage in a behavior known as “terminal altruism,” where they remove themselves from the colony to die.
The findings from this study, titled “Altruistic disease signaling in ant colonies,” have been published in the journal Nature Communications. As scientists continue to explore the intricacies of ant behavior, this research sheds light on the complex social dynamics within ant colonies and reinforces the idea that cooperation and self-sacrifice play crucial roles in their survival.
