In underground chambers where carbon dioxide accumulates, some ant species have not only adapted to life in such an environment but also use its unique features for their own benefit. Instead of completely removing carbon dioxide to the outside, part of it is transformed by the insects into a durable mineral layer that strengthens their exoskeleton.

Life Features of Leafcutter Ants

Leafcutter ants, which cultivate fungi, are considered unique farmers among insects. Some species collect fresh leaves and use them as a substrate for growing fungi, while others utilize detritus and fallen plant parts. The fungi grown in their nests serve as the main food source for the numerous members of the colony.

However, this underground “farming” faces the challenge of ventilation. In colonies where millions of ants live together, fungi grow, and plant debris decomposes, the concentration of carbon dioxide (CO2) in the chambers can rise significantly. Natural gas exchange with the surface is difficult, and without air renewal, the atmosphere inside the nest becomes unsuitable for breathing.

Although leafcutter ants have mechanisms to remove CO2 from the nest, their effectiveness varies among species, and not all can ensure perfect ventilation.

Biomineralization in Ants

Research into the structure of ant nests and their methods of regulating gas exchange has been ongoing for a long time, but the role of the ants’ body surface and their microbiota in this process remained unclear. In 2020, it was discovered that worker ants of Acromyrmex echinatior possess a unique biomineral armor made of calcite crystals distributed across the surface of their chitinous shell. This layer significantly increases the strength of their exoskeleton and serves a protective function.

The reasons for biomineralization in leafcutter ants are not fully understood, but it is believed that bacteria of the genus Pseudonocardia, which live in symbiosis with Acromyrmex echinatior, play a key role. These bacteria likely initiate carbonate precipitation or participate in converting CO2 into solid carbonate minerals.

New Findings on Sericomyrmex amabilis

Another research group found that Sericomyrmex amabilis ants, which inhabit Central and South America and are close relatives of leafcutters, are also capable of biomineralization. However, this species has not yet been found to have symbiotic bacteria similar to those discovered in Acromyrmex echinatior. If this is confirmed, Sericomyrmex amabilis could become the first known animals to independently evolve the ability to convert gas into mineral during evolution, without the help of bacterial partners.

To test the biomineralization ability of Sericomyrmex amabilis, scientists used methods such as stable carbon isotope tracing, nanoscale secondary ion mass spectrometry, and solid-state nuclear magnetic resonance with carbon-13 isotope. The results showed that ants remove part of the CO2 through ventilation systems, while another part is converted into a strong biomineral layer covering their exoskeleton.

Composition and Features of the Mineral Layer

This layer contains dolomite—a carbonate mineral with the formula CaMg(CO3)2, which is difficult to synthesize in laboratory conditions. Its structure includes calcium, magnesium, and carbonate groups. In the lab, dolomite synthesis is challenging due to the strong hydration of magnesium, which hinders its incorporation into the calcium carbonate crystal lattice and slows crystal growth.

In nature, the formation of dolomite usually takes from several thousand to millions of years, especially when it comes to forming structurally ordered minerals. At low temperatures and pressures, calcium and magnesium ions require significant time to form an ideal crystal lattice.

Studies have shown that Sericomyrmex amabilis can create partially ordered dolomite quite rapidly and at relatively low temperatures. The mechanism of this process is still unclear, and further research will focus on exploring the “chemical kitchen” of ants and the molecular mechanisms of biomineralization.

The Importance of Biomineralization

Biomineralization solves two problems for insects at once. First, the mineral layer strengthens their exoskeleton, providing protection against external threats. Second, this process allows them to get rid of excess carbon dioxide inside the nest.