For more than 500 million years, animal bodies have incorporated minerals to build tough structures like bones, teeth and armored shells. But no one has ever seen such armor in insects — until now.
According to research published in the journal Nature Communications, scientists have discovered a whitish, granular coating on mature workers of a species of leaf-cutter ant (Acromyrmex echinatior) found in Central America and Mexico.
The magnesium-rich calcite armor likely helps protect against a harmful fungus (Metarhizium anisopliae) and attacks by much larger soldier ants.
Co-author Jeffrey Sosa-Calvo worked on the research while a postdoctoral fellow at Arizona State University. He was surprised no one had seen such biomineral armor before, since insects evolved from crustaceans.
"So it's interesting because it seems to be common, I think, in crustacea, but no one has found it before in insects," Sosa-Calvo said.
Also remarkable is the prevalence of magnesium in the armor. Calcium carbonate — which forms the hard parts of corals, mollusk shells and sea urchin spines — is far more common.
Sosa-Calvo is currently a postdoc at the Smithsonian National Museum of Natural History in Washington, D.C.
Leaf-cutting ants are a subgroup of fungus-growing ants. They harvest fresh vegetation and use it as a sort of topsoil for growing crops of beneficial fungus.
Discovering biomineral armor in such a well-studied species could mean other examples exist undiscovered in the insect world, perhaps hiding in plain sight.
