orco Mutagenesis Causes Loss of Antennal Lobe Glomeruli and Impaired Social Behavior in Ants

Life inside ant colonies is orchestrated with diverse pheromones, but it is not clear how ants perceive these social signals. It has been proposed that pheromone perception in ants evolved via expansions in the numbers of odorant receptors (ORs) and antennal lobe glomeruli. Here, we generate the first mutant lines in the clonal raider ant, Ooceraea biroi, by disrupting orco, a gene required for the function of all ORs. We find that orco mutants exhibit severe deficiencies in social behavior and fitness, suggesting they are unable to perceive pheromones. Surprisingly, unlike in Drosophila melanogaster, orco mutant ants also lack most of the ∼500 antennal lobe glomeruli found in wild-type ants. These results illustrate that ORs are essential for ant social organization and raise the possibility that, similar to mammals, receptor function is required for the development and/or maintenance of the highly complex olfactory processing areas in the ant brain. [Display omitted] [Display omitted] •We generated odorant receptor co-receptor (orco) mutants in an ant•orco mutants did not follow pheromone trails or cluster with other ants•Mutant ants also had greatly reduced antennal lobes in the brain•Odorant receptors are essential for the complex organization of ant societies Development of the first line of mutant ants, using CRISPR/Cas technology, reveals what happens inside of a colony when ants lose the ability to recognize odors.