Ants, like other animals, smell to find food and to tell enemies from nestmates. They also communicate by detecting pheromones, hormones released into the air. It is no exaggeration to say that ant society runs on "smell." Researchers have found that ants' sophisticated olfactory system works because each neuron senses only one odor at a time.
A team at Rockefeller University in the United States said in the international journal Current Biology on the 19th (local time) that it discovered that when ants' olfactory neurons (nerve cells) operate, they select and use only a single odor gene out of hundreds.
Ants detect odors with their antennae. When an odor molecule binds to its matching receptor protein, a neuron can detect it. Ants have about 300–500 olfactory receptor genes, allowing them to sense a wide range of chemical odors. These include pheromones that guide communication and trails, food odors such as sugar and protein, and cuticular hydrocarbons that distinguish nestmates from foes. They also detect odors from sick nestmates.
The researchers identified which receptor genes activate when ants smell with their antennae. The study used Ooceraea biroi, which shows complex social behavior. This ant is a raider ant that invades other nests to steal eggs or larvae for food. A scout ant locates prey, returns home to alert nestmates, and then a group attack begins.
Unusually, Ooceraea biroi is called a "clonal" raider ant because it reproduces by cloning instead of mating. While other ants lay eggs after the queen and males mate, raider ants reproduce by thelytokous parthenogenesis, in which females lay eggs on their own.
Analysis showed that when raider ants smell, only a single receptor gene is active in each neuron. When a neuron activates a specific odor gene, nearby genes are also copied in the process. If all of these produced receptors, the sense of smell would inevitably be noisy.
However, the copies of other genes could not exit the cell and therefore did not function. As a result, surrounding genes are locked and sources of interference are blocked, allowing a neuron to detect exactly one odor signal. The same principle applies whether ants are detecting pheromones or smelling other chemicals.
The researchers explained that this mechanism is a new mode not seen in other organisms previously known.
Fruit flies have only about 60 olfactory receptor genes and operate with a simple switch in which one turns on in a neuron and the rest turn off. Mammals have hundreds of odor genes, but the operating principle is similar to that of fruit flies: one odor gene turns on at random and the rest turn off. In previously studied organisms, this simple one-on, rest-off mode was typical.
Ants, like mammals, possess hundreds of odor genes, many of which cluster closely together. Because of this, using a simple switch like fruit flies would risk turning on neighboring genes as well. In this study, the researchers reported discovering a new regulatory principle that ensures exactly one odor gene turns on per neuron. Even if other genes are transcribed, their copies cannot leave the cell and thus cannot produce receptors. In effect, even if signals arise, the noise cannot get out.
Daniel Kronauer, a professor of biology who led the study, said, "With this method, ants can rapidly evolve new odor genes without wrecking their existing olfactory system," adding, "Once such a system takes hold, it can develop into an increasingly complex olfactory apparatus."
References
Current Biology (2025), DOI: https://doi.org/10.1016/j.cub.2025.09.026