Amazing stuff!
"Adult ants that have been infected with deadly pathogens often leave the colony to die so as not to infect others. But, “like infected cells in tissue, [young ants] are largely immobile and lack this option,” said ... a researcher ... who studies how social insects such as ants fight diseases collectively as superorganisms, in a statement. ..."
"Ant colonies operate as tightly coordinated “superorganisms” with individual ants working together, much like the cells of a body, to ensure colony health. Researchers ... have now discovered that terminally ill ant brood, like infected cells in a body, release an odor signaling their impending death and the risk they pose. This sophisticated early warning system facilitates rapid detection and removal of pathogenic infections. ...
Upon receiving the signal, worker ants respond swiftly by unpacking the terminally ill pupae from their cocoon, creating small openings in their body surface and applying their antimicrobial poison, formic acid, which functions as a self-produced disinfectant. While this treatment immediately kills the pathogens multiplying inside the pupa, it also results in the pupa’s own demise. ..."
From the abstract:
"Sick individuals often conceal their disease status to group members, thereby preventing social exclusion or aggression. Here we show by behavioural, chemical, immunological and infection load analyses that sick ant pupae instead actively emit a chemical signal that in itself is sufficient to trigger their own destruction by colony members.
In our experiments, this altruistic disease-signalling was performed only by worker but not queen pupae. The lack of signalling by queen pupae did not constitute cheating behaviour, but reflected their superior immune capabilities. Worker pupae suffered from extensive pathogen replication whereas queen pupae were able to restrain their infection.
Our data suggest the evolution of a finely-tuned signalling system in which it is not the induction of an individual’s immune response, but rather its failure to overcome the infection, that triggers pupal signalling for sacrifice. This demonstrates a balanced interplay between individual and social immunity that efficiently achieves whole-colony health."
Sick, Immobile Young Ants Send “Kill Me” Signal to Colony Workers | The Scientist "Cocooned ants infected with a deadly fungus call on workers to kill them to protect the colony—the first example of altruistic disease signaling in social insects."
