Emergency surgery in the insect state: Researchers have observed amputations in a species of ant. Florida carpenter ants deliberately bite off injured limbs of their nestmates to ensure their survival. The measure is also apparently carried out “carefully”: whether the treating ant decides on amputation or wound cleaning depends on the location of the injury. The studies show that this is important for the healing process. The researchers now want to clarify how widespread this complex behavior could be among ants.
Together they are strong: through cleverly regulated cooperation, the many individuals of an ant colony form an astonishingly efficient unit. Parallels to the concepts of human societies are repeatedly apparent. This also applies to medical care: studies have already provided fascinating insights into the sophisticated health management of ant colonies. It was already known that ants treat wounds in injured nestmates. They are cleaned and, in some species, treated with antimicrobial substances to prevent infections.
The researchers led by Erik Frank from the University of Würzburg focused on the ant species Camponotus floridanus, which is found in the southeast of the USA. The team is interested in these so-called Florida carpenter ants because, like some other species, they do not produce antibiotic-effective secretions in glands to treat infected wounds. This raised the question of whether they use other strategies to treat injuries in nestmates, which often occur in interspecies fights among ants.
If the thigh is injured, amputation is performed
Observations of the Florida carpenter ants initially showed that wounds are treated mechanically: the insects clean them using their mouthparts. But then the team also observed another form of treatment that was previously only known from human emergency medicine: the Florida carpenter ants amputate injured limbs as a precautionary measure in order to save the lives of wounded nestmates. The leg is bitten off at the so-called trochanter, which connects an element on the insect’s body to the thigh.
The “patients” seem to cope well with the treatment and the loss of one of their six legs: around 90 percent survive and can continue to take on tasks in the community. The researchers documented how useful amputation can be through experiments: cutting off an injured leg prevents life-threatening wound infections from spreading in the ants’ bodies. Without treatment, however, the survival rate in the case of infected wounds was less than 40 percent. “This is the first known case of a sophisticated and systematic amputation in the animal kingdom,” says Frank.
However, the researchers were able to document another astonishing aspect of the phenomenon: the ants apparently make “smart” decisions about when to carry out an amputation and when not to. It turned out that a leg is always bitten off if the thigh is injured. If, on the other hand, there is a wound on the lower leg, it is only cleaned mechanically, even if it is infected. However, this therapy then leads to a survival rate of only around 75 percent. This raised the question of why the ants do not also amputate legs with lower leg injuries.
Too little time for a successful amputation
The reason was revealed by computer tomography examinations of the ants’ legs. They showed that injuries to the thigh lead to a lower probability of bacteria spreading in the body due to effects on blood flow. In this case, amputation is therefore worthwhile. If, on the other hand, a lower leg is injured, bacteria can penetrate and spread very quickly in the body due to the special mechanisms in the ants’ circulatory system, the researchers explain. The time window for a successful amputation is therefore very narrow in this case. However, the ants usually need at least 40 minutes for this procedure.
“As the ants are unable to sever the leg quickly enough to prevent the spread of harmful bacteria, they try to reduce the likelihood of a fatal infection by spending more time cleaning a lower leg wound,” explains senior author Laurent Keller from the University of Lausanne. “Our study is the first to show that animals also use prophylactic amputations as part of wound treatment. And it shows that the ants adapt the treatment to the type of injury,” Keller concludes.
The researchers now want to investigate this fascinating behavior further. They are currently studying other ant species to determine how widespread “emergency surgery” might be in the critters’ health systems. Species living in Germany are also in their sights.
Source: Cell Press, University of Würzburg, scientific article: Current Biology, doi:
10.1016/j.cub.2024.06.021