Zoology: Mineral armour discovered in insects

The first known example of biomineral body armour discovered in the insect world is reported in Nature Communications this week. The discovery of the armour — widely seen among marine creatures — in a species of leaf-cutter ant (Acromyrmex echinatior) could have implications for our understanding of the evolution of armour and widens our knowledge of the use of biominerals in the natural world.

Biomineral skeletons evolved more than 550 million years ago. This type of armour has been observed in crustaceans, such as lobsters and other marine animals, but has not previously been seen in insects.

Cameron Currie and colleagues report the discovery of magnesium-rich calcite armour overlaying the exoskeletons of worker leaf-cutter ants from the species A. echinatior. The authors found that the armour develops as the ants mature, which increases the hardness of their exoskeleton, and covers nearly the entire body. They observed that worker ants with the biomineralized exoskeletons were more likely to survive in encounters with Atta cephalotes soldier ants than those without, and that the armour helped to protect them against infection from the disease-causing fungus, Metarhizium anisopliae.

Currie and co-authors conclude that the discovery of this armour in a relatively well-studied insect species suggests that it may be more widespread than previously thought.