Many creatures have been revealed to self-medicate, from bears using Osha root paste to repel insects to chimps eating rough leaves to reduce their parasite load. But a new study has now revealed that some wood ants take this to a whole new level: They craft their own antibiotics by mixing two separate substances, the only other creature than humans found to do so.
Researchers investigating how the ants keep their nests free of disease have shown how they use a mixture of tree resin and formic acid to produce the antibacterial cocktail that is then used to treat their brood within the colony. Published in the journal Ecology and Evolution, the authors suggest that this could be how packed nests avoid epidemics that could be devastating for the colony’s long-term survival.
The ants (Formica paralugubris) had already been known to collect large amounts of resin from coniferous trees and store it in the nurseries within the ant nests, in a similar way also seen with some bee species. The resin is rich in secondary metabolites that have antimicrobial properties, but that is seemingly not enough for these social insects.
In addition to the resin, the ants also produce formic acid, which is ordinarily used to spray at potential predators and prey. This chemical also has antimicrobial properties, and is frequently used by humans for this very reason, leading the researchers to have a hunch that the ants may be using the acid in a similar way. They decided to investigate whether or not the insects may have been mixing the two substances to create an antibiotic product that was better than the sum of its parts.
They tested fresh resin against resin that had been exposed to wood ants for a couple of weeks for their ability to ward off the fungus Metarhizium brunneum, which is known to infect ants and spread through their colonies. The ant-exposed resin was much more effective at keeping the fungus at bay, compared to both the fresh resin and other objects, such as sticks, that had also been exposed to the ants. This suggests that there was an important interaction occurring between the ants and the resin, which turned out to involve the poison they produce themselves.
The discovery that wood ants craft their own antibiotics by mixing two separate substances is one of the most complex examples of zoopharmacognosy yet discovered, and has been dubbed “defensive mixology”. The only other animal known to brew up antibacterial cocktails by mixing things together are humans, putting these little guys in a very select group indeed.
[H/T Science Mag]