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https://archive.is/lpgga
In his 11 years studying ant behavior, biologist Erik Frank had never seen anything like it. He and his colleagues at the University of Würzburg brought Florida carpenter ants back to their lab in Germany to learn how they respond to injury. Most ant species treat the injured or severed limb of a comrade by coating it with an antimicrobial goo. But the reddish-brown carpenter ants took a different tack: They bit the remainder of the limb off, effectively amputating it.
Other animals, such as lizards, shed their own limbs to escape predators, but Frank says this is the first case of an insect severing the leg of a nestmate to save its life. The only other species that does this is humans. “I didn’t believe this at all because it was very counterintuitive,” he says. “I repeated the experiment four times before I accepted it.”
Most ant species have glands that secrete antimicrobial compounds to stave off fungal and bacterial infections, which commonly enter their bodies through wounds. But the Florida carpenter ant (Camponotus floridanus)—a centimeter-long insect native to the southern United States—lost that gland over evolutionary time. To figure out how the species fends for itself, Frank’s team cut the ants’ legs at the femur and exposed the wound to Pseudomonas aeruginosa, a bacterium commonly found in soil. The team left some of the ants in isolation and returned others to their nest.
The ants that returned to the nest were quickly approached by one or two comrades, which gnawed the leg above the femur, amputating it entirely. Ninety percent of the ants that got this “surgery” survived. In contrast, only 40% of those left alone lived.
With a pair of microscissors, the researchers also injured the ants’ legs lower down, at the tibia. This time, fellow insects did not amputate the appendages of their injured nestmates; instead, they simply licked the wound to remove bacteria with their tongues. Ninety percent of the isolated ants died, whereas 75% of those that returned to the nest survived.
The difference in the tactics employed by bystander ants may lie in the insects’ physiology. High-resolution microscopy revealed that the Florida carpenter ant’s femur has several muscles that impede circulation of hemolymph (the insect version of blood), stopping the bacteria from quickly entering the body. As a result, the ants may be more likely to amputate femur injuries because they have the time needed to perform this procedure, explains Daniel Kronauer, an expert on ant biology at Rockefeller University who was not involved with the research. The tibia, in contrast, has fewer muscles to stop hemolymph, making blood circulation quicker and allowing bacteria to enter faster. That means tibia injuries, must be treated more quickly, Kronauer says.
To find out whether amputations following tibia wounds are as effective at stopping infections as those following femur wounds, Frank’s team amputated the ants’ legs. An analysis of DNA in the ants’ bodies revealed that amputations following femur wounds indeed halted bacterial infections in their tracks, whereas amputations following tibia wounds did not. Contrary to what the researchers believed, tibia amputations didn’t improve the insects’ survival, and this is what the ants “seem to know,” Frank says.
Like their hierarchical social structure, amputation is another one of the surprising ways that ants have evolved “sophisticated behaviors” very similar to humans, Kronauer says. “It’s like retrieving injured soldiers from the battlefield and then treating them.”
The findings may change people’s perception of ants, says Christopher Pull, a biologist at the University of Oxford who wasn’t involved with the work. They’re not just soldiers who only work for the queen only to be replaced or discarded at any time, he says—they go to extreme lengths to help one another out.
https://archive.is/lpgga
Other animals, such as lizards, shed their own limbs to escape predators, but Frank says this is the first case of an insect severing the leg of a nestmate to save its life. The only other species that does this is humans. “I didn’t believe this at all because it was very counterintuitive,” he says. “I repeated the experiment four times before I accepted it.”
Most ant species have glands that secrete antimicrobial compounds to stave off fungal and bacterial infections, which commonly enter their bodies through wounds. But the Florida carpenter ant (Camponotus floridanus)—a centimeter-long insect native to the southern United States—lost that gland over evolutionary time. To figure out how the species fends for itself, Frank’s team cut the ants’ legs at the femur and exposed the wound to Pseudomonas aeruginosa, a bacterium commonly found in soil. The team left some of the ants in isolation and returned others to their nest.
The ants that returned to the nest were quickly approached by one or two comrades, which gnawed the leg above the femur, amputating it entirely. Ninety percent of the ants that got this “surgery” survived. In contrast, only 40% of those left alone lived.
With a pair of microscissors, the researchers also injured the ants’ legs lower down, at the tibia. This time, fellow insects did not amputate the appendages of their injured nestmates; instead, they simply licked the wound to remove bacteria with their tongues. Ninety percent of the isolated ants died, whereas 75% of those that returned to the nest survived.
The difference in the tactics employed by bystander ants may lie in the insects’ physiology. High-resolution microscopy revealed that the Florida carpenter ant’s femur has several muscles that impede circulation of hemolymph (the insect version of blood), stopping the bacteria from quickly entering the body. As a result, the ants may be more likely to amputate femur injuries because they have the time needed to perform this procedure, explains Daniel Kronauer, an expert on ant biology at Rockefeller University who was not involved with the research. The tibia, in contrast, has fewer muscles to stop hemolymph, making blood circulation quicker and allowing bacteria to enter faster. That means tibia injuries, must be treated more quickly, Kronauer says.
To find out whether amputations following tibia wounds are as effective at stopping infections as those following femur wounds, Frank’s team amputated the ants’ legs. An analysis of DNA in the ants’ bodies revealed that amputations following femur wounds indeed halted bacterial infections in their tracks, whereas amputations following tibia wounds did not. Contrary to what the researchers believed, tibia amputations didn’t improve the insects’ survival, and this is what the ants “seem to know,” Frank says.
Like their hierarchical social structure, amputation is another one of the surprising ways that ants have evolved “sophisticated behaviors” very similar to humans, Kronauer says. “It’s like retrieving injured soldiers from the battlefield and then treating them.”
The findings may change people’s perception of ants, says Christopher Pull, a biologist at the University of Oxford who wasn’t involved with the work. They’re not just soldiers who only work for the queen only to be replaced or discarded at any time, he says—they go to extreme lengths to help one another out.
