The social glue of ants is the sense of smell, or at least its equivalent, understood as the ability to perceive smells. When the ability to perceive odors is lacking, chaos reigns in the colonies, as demonstrated by a study that, for the first time, managed to genetically modify these insects to study their behavior.
The research of Rockefeller University represents a fundamental step in the study of the evolution of social behaviors that push living beings - in particular the members of the most crowded animal colonies - to cooperate to reach a goal.12 things you (perhaps) don't know about smell and smells
A real challenge. Deactivating or even identifying the genes that drive socializing in ants is a titanic undertaking. Hardly the eggs survive without the workers, and the complex life cycle of the individuals (from egg to larva, to pupa, up to the adult stage) means that it can even take years to obtain a genetically modified population.
The stroke of genius. Thus the researchers have resorted to a "shortcut". They have studied a species of invasive ant, the Ooceraea biroi, which has no queens in its colonies but reproduces by parthenogenesis. In other words, each individual lays unfertilized eggs, which develop as clones. In this way it was possible to replicate genetically modified DNA in eggs more quickly, using CRISPR molecular precision scissors.
Mad splinters. The scientists deactivated a gene called ogre, which encodes an essential protein for the perception of odors through antennas. The genetically modified ants, unlike what usually happens, did not spend the first month of their life together with their peers but they started to wander immediately after hatching; later they proved incapable of following the odorous traces of other individuals and died after 2-3 months instead of after 6-8. They were also less prolific, laying only one egg every two weeks, instead of 6 as is usually the case.
Finally, no tangles of odor-related receptors called glomeruli have formed in their brains. The difficulty in perceiving odors has therefore directly affected brain development, and the organization of the colony.