1Laboratoire d'éthologie et pharmacologie du comportement and Institut de Recherche sur la Biologie de l'Insecte, Faculté des Sciences, Université François Rabelais, 37200 Tours, France.
2Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.
Social isolation is an unusual situation in ants that normally keep frequent contacts with their nestmates. After being isolated for few days, workers of Camponotus fellah engage in long trophallaxis when they are reunited with their nestmates. Long trophallaxis allow them to re-adjust their individual cuticular hydrocarbon profiles to the cuticular profile of their non isolated nestmates. Therefore, they can be re-integrated in their mother colonies without being attacked by guardians. An octopamine administration to 5-day isolated workers one hour before being reunited with nestmates leads to a decrease of their urge to trophallax. This decrease is not due to any modification of the general activity and it is specific since it is reversed by an administration of the octopamine antagonist phentolamine. Octopamine also leads to a reduction of the hydrocarbons transfer between nestmates. We propose that social isolation leads to reduction of octopamine (as do social isolation to brain noradrenaline in some vertebrate species) that may mediate the need for trophallaxis. Therefore, an octopamine injection could bypass the isolation effect on the behaviour and on the homogenisation of the colony odour.