Odorant coreceptor which complexes with conventional odorant receptors (ORs) to form odorant-sensing units, providing sensitive and prolonged odorant signaling and calcium permeability (By similarity). Obligate coreceptor of all odorant receptors (By similarity). Orco is a universal and integral part of the functional odorant receptor, involved in the dendritic localization of other olfactory receptors. Can form functional ion channels in the absence of an odor-binding odorant receptor (By similarity). Plays a central role in the perception of olfactory stimuli in ants and is essential for ant social organization (PubMed:28802043). Required for pheromone sensing and mating behavior (PubMed:28802043). Also required for the development and maintenance of odorant receptor neurons (ORNs) and of antennal lobe glomeruli (PubMed:28802043). Heterodimer with conventional odorant receptors (ORs). Impaired behavior and decreased reproductive performance, probably due to loss of pheromone sensing. Ants show strongly decreased sensitivity to various pure semiochemicals delivered in puffs of air, and display increased levels of wandering outside of the nest. In a solitary environment, homozygous mutants also display an abnormal antennal twitching behavior: they quickly move their antennae, similar to the quick antennal movement observed during dueling among workers in the transition to gamergates. Mating and reproduction are impaired: worker dueling and the transition to gamergates in the absence of a reproductive queen or gamergates. Ants also display gross neuroanatomical defects in the antennal lobe, with a dramatic decrease in the number of odorant receptor neurons and antennal lobe glomeruli. In contrast to most eusocial ant species, where only the queen can transmit genetic information, workers in H.saltator ants can be converted into gamergates (pseudoqueens) that can found entire colonies, facilitating genetic studies (PubMed:28802043). Belongs to the insect chemoreceptor superfamily. Heteromeric odorant receptor channel (TC 1.A.69) family. Orco subfamily. Whispers - Issue 197 of November 2017