Ants deliberately amputate the legs of conspecifics
Some ants act as surgeons. If a fellow ant's leg is wounded, they bite it off in order to save the life of their colleague. They adapt the treatment depending on the type of injury.
It's a radical approach: Florida wood ants (Camponotus floridanus) bite off the wounded limbs of conspecifics to prevent them from dying of infections. They proceed differently depending on the type of injury: They do not amputate or only amputate certain parts of the leg, as researchers at Julius-Maximilians-Universität Würzburg show.
For the experiments, they deliberately injured individual animals and then observed how other ants reacted to this. They discovered that the ants only amputate their fellow ants when they injure their thigh - regardless of whether the wound was sterile or bacterially infected. Biting off the leg prevents bacteria from spreading further in the body, which drastically increases the ants' chances of survival. Around 90 per cent of the amputated animals survive the treatment. Despite losing one of their six legs, they are then able to resume their full range of tasks.
In the case of injuries to the lower leg, however, the ants refrained from this measure. Instead, they invest time in cleaning the wound and lick it intensively. This was associated with a survival rate of around 75 per cent. But why don't the ants amputate in this case? Wouldn't the chances of survival then perhaps be greater? This was also investigated: The research team carried out amputations themselves on ants with wounded and bacterially infected lower legs. The surprising result: the survival rate was only 20 per cent.
The experts explain this as follows: If the lower leg is wounded, the bacteria penetrate the body very quickly. The ants "know" that there is little chance of salvation in the event of an amputation in this case and prefer to invest time in intensive cleaning. In the case of a thigh injury, however, the haemolymph flow is impaired, meaning that pathogens spread more slowly, leaving more time for amputation.
The ant species investigated in the study is found in the south-east of the USA. The reddish-brown animals are relatively large, measuring up to 1.5 centimetres in length. They nest in rotting wood and defend their nest vigorously against rival ant colonies. If fights break out, there is a risk of injury. The research team chose this species because they do not have a metapleural gland. With this gland, other ant species produce an antibiotically effective secretion that they apply to infected wounds. This raised the question of what other means Camponotus ants use to combat infections. That these were amputations was a big surprise, according to the authors.
Spectrum of science
We are partners of Spektrum der Wissenschaft and want to make well-founded information more accessible to you. Follow Spektrum der Wissenschaft if you like the articles.
Original article on Spektrum.de
Experts from science and research report on the latest findings in their fields – competent, authentic and comprehensible.