These ants dress in a protective ‘biomineral armor’ never seen before in insects

Ants are rather organized little creatures. Highly social insects, they know how to forage, build complicated nests, steal pantry snacks, and generally take care of the queens and the colony, all working together.

Leaf cutter ants increase this collaboration by several levels. Colonies of leaf cutter ants like Acromyrmex echinatior it can contain millions of ants, divided into four castes which all have different roles in maintaining a mushroom garden that the ants eat.

These farm ants might make for a top-tier gardening team, but that doesn’t mean they don’t get into the occasional waste and living in such large groups usually also means facing an increased risk of pathogens.

For these reasons, a little bit of protection never goes astray, and while scientists aren’t entirely sure why, it appears these little boys needed enough protection to develop their own natural armor.

A team led by University of Wisconsin-Madison researchers analyzed this “whitish granular coating” A. echinatior and came to the conclusion that the coating is a self-made biomineral armor, the earliest known example in the insect world.

“We have been working on these leaf cutter ants for many years, particularly focusing on this fascinating association they have with the bacteria that produce antibiotics that help them cope with disease,” Cameron Currie, senior author and microbiologist at the University of Canada, told ScienceAlert. Wisconsin-Madison.

“It was in our effort to identify what the ant could produce for that bacteria [first author Li] Hongjie discovered biomineral crystals on the ant’s surface. “

The team peered deeply into the mineral layer covering the ant’s exoskeleton, using electron microscopy, electron backscatter diffraction and a number of other techniques. They found that the coating consists of a thin layer of rhombohedral magnesium calcite crystals about 3-5 micrometers long.

close-up of the ant bioarmorAbove: the shiny armor. Bottom: SEM image of the coating. (Li et al., Nature Communications, 2020)

You may be more familiar with biomineral skeletons in crustaceans such as the hard shells of lobsters. However, insects evolved from crustaceans, so it makes sense that some may have retained an armor-like trait.

The team also bred the ants to see when this coating has occurred and how it protects them, finding that the coating is not present in baby ants, but develops rapidly as the ants mature and this finished coating hardens significantly. the exoskeleton.

To confirm this, the researchers put the ants in experimental battles, finding that those with armor were more protected in battle, and also from pathogens.

“To further test the role of the biomineral as protective armor, we exhibited Acromyrmex echinatior large workers with and without biomineral armor a Atta cephalotes soldiers in ant aggression experiments designed to mimic territorial “ant wars” which are a relatively common occurrence in nature, “the team writes.

“In direct combat with the substantially larger and stronger A. cephalotes soldier workers, ants with biomineralized cuticles lost significantly fewer body parts and had significantly higher survival rates than biomineral free ants. “

They also found that without the armor, the ants were much more likely to be infected with an insect-attacking fungus called Metarhizium anisopliae.

While we don’t understand how this leaf-cutting ant species developed this coating, the team thinks it’s probably not the only insect that has developed such protection.

‘Given that mushroom-growing ants are among the most widely studied tropical insects,’ the team writes, ‘our finding raises the intriguing possibility that biomineralization of high-magnesium calcite may be more prevalent in insects than previously. suspected earlier, suggesting a promising avenue for future research. “

While there may be a number of ant species that have similar coatings, with further research the “armor” technology may even make the leap to humans, or at least our stuff.

“We believe there is potential for material development as it adds strength to a range of products. It is light and thin,” Currie told ScienceAlert.

“The field of materials science is an exciting area of ​​science.”

The research was published in Nature Communications.


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