These ants suit up in a protective ‘Biomineral Armor’ never seen before in insects

Ants are very organized and social creatures. They are experts in foraging, building complicated nests, and also looking after the queen and the colony. Leafcutter ants (Acromyrmex echinatior) have raised the bar a bit higher. Leafcutter ants can contain millions of ants divided into four castes, assigned tasks with the common purpose of maintaining the fungus that the ants eat. 

Though the farming ants make a top-tier team of gardeners they also get into occasional scrap, which increases the risk of harmful pathogens. This might be the reason the ants have developed the armor they have. A team led by the University of Wisconsin Madison analyzed the whitish granular coating on the ant and concluded that it was the first known example of self-made biomineral armor in any insect. 

“We have been working on these leaf-cutting ants for many years, especially focusing on this fascinating association they have with bacteria that produce antibiotics that help them deal with diseases,” senior author and University of Wisconsin-Madison microbiologist Cameron Currie told ScienceAlert. “It was in our effort to identify what the ant might produce for the bacteria that [first author Li] Hongjie discovered the biomineral crystals on the surface of the ant.”

The team examined the biochemicals made using electron microscopy, electron backscatter diffraction, and a number of other techniques and found that they are built of rhombohedral magnesium calcite crystals with the size of 3-5 nanometres. 

These biomineral armors are seen in crustaceans too, for instance, lobsters. Insects have evolved from crustaceans, so it makes sense that some may have retained a similar armor. 

The team also reared some labs to see how the armor protects them. It was found that the armor is absent in babies but grows as the ants mature, hardening the exoskeleton. The team discovered that in the experimental battle ants having biomineral armor were better protected and lost significantly fewer parts. “To further test the role of the biomineral as protective armor, we exposed Acromyrmex echinatior major workers with and without biomineral armor to Atta cephalotes soldiers in ant aggression experiments designed to mimic territorial ‘ant wars’ that are a relatively common occurrence in nature,” the team wrote. “Indirect combat with the substantially larger and stronger ant cephalotes soldier workers, ants with biomineralized cuticles lost significantly fewer body parts and had significantly higher survival rates compared to biomineral-free ants.”

They also discovered that without the armor, the ants were significantly more likely to be infected with an insect attacking fungus called Metarhizium anisopliae. The team thinks that it’s probably not the only insect that developed such protection. “Given that fungus-growing ants are among the most extensively studied tropical insects,” the team writes, “our finding raises the intriguing possibility that high-magnesium calcite biomineralization may be more widespread in insects than previously suspected, suggesting a promising avenue for future research.” While there might be a number of species of ants that have a similar coating, with more research the ‘armor’ technology could even make the leap to humans – or at least our materials. “We think that there is potential for the development of the material as adding strength to a range of products. It is light and thin,” Currie told ScienceAlert. 




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