Brain Injection Permanently Changes Ants' Behavior

Florida carpenter ant majors, the larger ants seen here, which normally protect the nest from intruders, can be made to act like the smaller ants (called minors) and forage for food—by injecting their brains with enzymes that alter their epigenetics. AAAS/Carla Schaffer

Carpenter ants have a rigid caste system made up of majors and minors. The former grow big and brawny, and they act as guards to defend the nest against intruders. The latter remain small, and they generally forage for food and help care for the queen.

Strangely, however, these ants have identical genes. So how could they turn out so differently in appearance and behavior? The answer lies in epigenetics, in which genes are turned on or "expressed" based on external factors such as the environment in which the animal develops and the food it eats.

In a study published January 1 in the journal Science, researchers found that they could alter the epigenetics of ants, as well as their behavior, by injecting various enzymes into their brains. Immediately after injecting newly hatched majors, the ants began acting like minors and foraging for food.

"These are long-term, permanent changes that occur when we inject the brain with these chemicals," Shelley Berger, a study co-author and epigeneticist at the University of Pennsylvania, told The New York Times.

The scientists found that the injection changes the way a single gene, called Rpd3, is expressed or is "read" to create proteins. This sets off a cascade of further changes that alters the way the ant behaves, Ars Technica explained.

The finding suggests the epigenetic changes may govern how insects handle division of labor and social behavior, and that such alteration could have similar impact in other animals, including mammals.