It sounds like a scene from a Spielberg film: an injured worker undergoes an emergency amputation, performed by one of her colleagues, which allows her to live another day. But this is not a human story – this is behavior seen in ants.
While this is not the first time wound care has been seen in ants, scientists say their discovery is the first example of a non-human animal performing life-saving amputations, with the operation being performed to treat leg wounds and the initiation or spread to prevent of infection.
And surprisingly, the insects seem to adapt the treatment they give to the site of injury. “The ants are able to, to some extent, diagnose the wounds and treat accordingly to maximize the survival of the injured,” said Dr. Erik Frank. , from the University of Lausanne and the first author of the research.
Write in the journal Current BiologyFrank and colleagues report how they cut Florida carpenter ants (Camponotus floridanus) on their right hind limb, then observed the reactions of their nestmates for a week.
The results revealed that 13 of 17 ants with injuries to their femur or thigh had been amputated by their nestmates, with their limb severed at the trochanter – the joint with the hip bone.
“Nestmates would begin to lick the wound before moving up the injured limb with their mouthparts until they reached the trochanter. The nestmates then proceeded to repeatedly bite the injured leg until it was severed,” the team wrote.
In contrast, no amputations were observed for the nine ants with injuries to their tibia, or lower leg. Instead, these ants only received wound care from their nestmates in the form of licking.
The team recorded similar results when the setup was repeated with ants with infected wounds.
Another set of experiments revealed that isolated ants with infected wounds were much more likely to die than those with sterile wounds. However, their survival rates improved significantly if the injured ants were either returned to their colonies – suggesting that the treatments provided by their nestmates were beneficial – or the infected limb was amputated by researchers, although this only provided benefits for upper leg wounds.
Frank said it was counterintuitive at first that amputations weren’t also beneficial for lower leg wounds. However, further work suggested that thigh wounds, but not lower leg wounds, were associated with damage to structures that pumped a blood-like substance around the ants’ bodies. As a result, infections of the lower leg spread around the body much faster than those of the upper leg, meaning that amputation of the former did little to improve survival.
Frank said ants were most likely to be injured in territorial disputes with neighboring colonies, but treating the wounded had benefits.
“We see in this Camponotus species that about 10-11% of the ants that go hunting or foraging carry an injury from a previous day. So they still make up an important part of the colony,” he said.
Prof Francis Ratnieks, at the University of Sussex, who was not involved in the work, said he was not surprised by the results. “This is another example of an adaptation in the lives of social insect workers in which workers help each other to work for their colony and help their colony,” he said.
“Like when a worker honey bee does a waggle dance to lead a nestmate to food, or when a worker sacrifices his life in defense of the colony, or here where workers amputate the limbs of an injured or infected worker. “
