Last year one species of ant was caught using antibiotics – now, another has been spotted performing amputations.
Researchers have just confirmed with experiments that this operation and other treatments that the ants offer each other really do save the ants’ lives.
While we’ve known for several years that ants treat each other’s wounds, we’re just learning how surprisingly complex and precise ant medical care can be.
“Ants are able to diagnose a wound, see if it’s infected or sterile, and treat it consistently over long periods of time from other individuals,” explains behavioral ecologist Erik Frank from the University of Würzburg in Germany.
“The only medical system that could rival that would be the human one.”
Frank and colleagues analyzed leg injuries in carpenter ants in Florida (Camponotus floridanus). When wounds on the leg-like tibia were left unattended, only 15 percent of the ants survived.
But if nestmates were allowed to tend to the wounds, the survival rate of the injured ants increased to an incredible 75 percent.
Wounds of the tibia were treated with mouth cleaning, in which the medic ant held the injured delicate limb with its mandibles and forelegs, licking the wound for long periods.
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But when carpenter ants encountered nestmates with injuries to what would be the equivalent of our thighs, the tiny surgeons first cleaned the wound before amputating the leg. This involved repeatedly biting the damaged limb until it snapped off.
The survival rate increased from 40 percent for ants with untreated femoral wounds to about 90 percent after amputation.
However, ants have never amputated legs with wounds near the tibia. So Frank and his team experimentally amputated the limbs of tibia-damaged ants to find that survival of these ants did not increase.
“In the tibia injuries, the flow of hemolymph was less obstructed, meaning bacteria could enter the body faster. Whereas in the femur injuries, the speed of blood circulation in the leg slowed down,” says Frank.
Ants take 40 minutes to complete a surgical amputation on a nestmate’s leg.
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“Thus, because they are unable to cut the leg fast enough to prevent the spread of harmful bacteria, ants try to limit the probability of fatal infection by spending more time cleaning the tibial wound,” explains evolutionary biologist Laurent Keller from the University of Lausanne. In Switzerland.
Infections are a major threat to animals, especially in social species where the risk of transmission is increased by close living.
Insects are known to mitigate some of these risks by destroying infected broods or letting the nest die in isolation.
Medical care for nestmates is likely another such strategy, but how it arose in ants is an intriguing question, given that 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 keen to experiment further to find out more.
“When you watch the videos where you have the ant presenting the injured leg and letting the other one bite completely voluntarily, and then presenting the newly made wound so another one can be completed. [the] the cleaning process – this level of innate collaboration to me is pretty amazing,” says Frank.
This research was published in Current Biology.