Ants remove limbs of their nestmates to prevent infection

Some ants will bite off the infected limbs of their nestmates to improve their chances of survival, making them the only non-human animals documented to amputate a limb to save the life of another animal.

Ants are already known to be one of the few animals that treat the wounds of their fellow creatures.Megaponera analisFor example, bacteria can treat infections by secreting antibacterial substances that are secreted from special glands.

But not all ant species have these glands, he said. Eric Frank “We wanted to know what would happen to the ants when they couldn’t use antibiotics,” said researchers from the University of Würzburg in Germany.

If you look closely at a colony of Florida carpenter ants (Camponotus floridanus) In the lab, Frank’s colleague Danny Buffatto of the University of Lausanne in Switzerland discovered ants biting off the injured legs of their nestmates.

“I didn’t believe it at first,” says Frank, “I thought there must be something else going on. Maybe there was a threat, or maybe the ants thought they were attacking an enemy.”

Analysing video footage from the colony, the team found many more cases of amputation, none of which showed any signs of resistance, and moreover, these amputations were only performed on animals in the thigh area.

To investigate further, the team injured the femurs of 72 carpenter ants and infected them. Half of the ants had their legs amputated by the researchers, while the rest served as controls. Mortality rates of the amputated ants were 90 percent lower than those of the controls, suggesting that the treatment successfully prevented the spread of the pathogen.

In contrast, in other ants, amputations never occurred when the wounds were on the ants’ lower legs, and when the team repeated the experiment with lower-leg injuries, the amputation and control groups died at the same rate. This may be due to the ants’ physiology, Frank says. “Insects don’t have a central heart like humans do,” he says. Instead, several muscles pump blood around the body, and by using micro-CT scanning, the team found that many of these muscles are concentrated in the carpenter ants’ upper legs.

This means that amputating the upper leg would damage the muscles that pump blood, restricting blood circulation and allowing the infection to spread, whereas amputating the lower leg would not prevent the infection from spreading because it does not have these muscles.

“This discovery is remarkable and pushes the boundaries of our understanding of the behavioral immune system of social insects,” said Dr. James Traniello At Boston University in Massachusetts.

Tomer Chakkes Researchers at the University of Regensburg in Germany were surprised at how targeted the amputations were: “They don’t just do amputations for any injury, but only when it makes sense.”

“It’s unlikely that the ants understand the ultimate reasons why these cuts work; rather, it’s more likely that this is an innate behavior that they’re ‘born’ with,” he says.