Last year, one species of ant was caught using antibiotics. Now, another species has been spotted performing amputations.
Researchers have recently confirmed experimentally that this operation and the other treatments ants give each other do indeed save ants’ lives.
We’ve known for a few years that ants treat each other’s wounds, but we’re only just beginning to realize how astonishingly complex and precise medical care for ants can be.
“Ants can diagnose a wound, see if it is infected or sterile, and then treat it with other individuals over a longer period of time,” explains behavioral ecologist Erik Frank of the University of Würzburg in Germany.
“The only medical system that can compete with that is the human system.”
Frank and colleagues analyzed leg injuries in carpenter ants in Florida (Camponotus floridanusWhen the wounds on the shin were not treated, only 15 percent of the ants survived.
But when nestmates were allowed to treat the wounds, the injured ants’ chances of survival increased to an incredible 75 percent.
The wounds on the shin were treated by cleaning the mouth. The treating ant held the vulnerable, injured limb with its mandibles and forelegs and licked the wound for a long time.
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But when the carpenter ants encountered nestmates with injuries to what would have been comparable to our thighs, the tiny surgeons would first clean the wound before amputating the leg, which involved repeatedly biting the injured limb until it was severed.
Survival rates increased from 40 percent in ants with untreated thigh wounds to about 90 percent after amputation.
However, the ants never amputated legs with wounds to the tibia. So Frank and his team experimentally amputated ant limbs with injuries to the tibia to find that the survival of these ants did not increase.
“In tibial injuries, the flow of hemolymph was less obstructed, meaning that bacteria could enter the body more quickly. Whereas in femur injuries, the speed of blood circulation in the leg was slowed,” says Frank.
It takes ants 40 minutes to perform a surgical amputation of their nestmate’s leg.
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“Because they can’t cut the leg quickly enough to prevent the spread of harmful bacteria, ants try to limit the chance of a deadly infection by spending more time cleaning the shin wound,” explains evolutionary biologist Laurent Keller of the University of Lausanne in Switzerland.
Infections pose a major threat to animals, especially in social species where the risk of transmission is greater because they live in close proximity to each other.
Insects are known to mitigate some of these risks by destroying infected broods or allowing the nest to die in isolation.
Medical care for nestmates is likely another of these strategies, but how it arose in ants is an intriguing question, since there is little evidence that they can learn. This suggests that such behavior may be innate, despite its complexity, the researchers suspect, but they are eager to conduct further experiments to learn more.
“If you look at the videos where the ant shows the injured leg and lets the other ant voluntarily bite it off, and then shows the newly made wound for another ant to finish, [the] “The cleaning process – this level of innate collaboration is something I find really striking,” says Frank.
This research was published in Current biology.