ARS | Publication request: Queen regulates biogenic amine level and nestmate recognition in fire ant, Solenopsis invicta, workers

Submitted to: Naturwissenschaften
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 29, 2008
Publication Date: August 13, 2008
Repository URL: http://www.springerlink.com/content/73x5475856514776/fulltext.html
Citation: Vander Meer, R.K., Preston, C.A., Hefetz, A. 2008. Queen regulates biogenic amine level and nestmate recognition in fire ant, Solenopsis invicta, workers. Naturwissenschaften. 95(12):1155-1158.

Interpretive Summary: Fire ants were inadvertently introduced into the United States early in the 1900s. They currently inhabit over 350 million acres in Puerto Rico and twelve southern states and more recently they have become established in isolated sites in California, Arizona, New Mexico, and Maryland. The fire ant’s large numbers and potent sting have resulted in medical, agricultural, and environmental economic impacts that cost the United States public billions of dollars each year. The ability of members of one colony to recognize members of another colony as different is a key feature of insect sociality. Understanding this process could lead to novel control strategies. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, USDA, ARS, Gainesville, Florida, and the Zoology Department, Tel Aviv University, Ramat Aviv, Israel demonstrated that worker brain levels of a neurohormone, octopamine, are low when the fire ant queen is absent and high when the queen is present, and that dietary octopamine given to queenless workers increased brain octopamine levels and worker recognition/aggression. This is the first demonstration of a link between the colony queen and biogenic amines in social insect nestmate recognition. Manipulation of biogenic amines could alter the dynamics of fire ant social structure and provide a novel way to reduce fire ant population levels.

Technical Abstract: Nestmate recognition is a critical element in social insect organization, providing a means to maintain territoriality and close the colony to parasites and predators. Ants detect the colony chemical label via their antennae and respond to the label mismatch of an intruder with aggressive behavior. In the fire ant, Solenopsis invicta, worker ability to recognize conspecific non-nestmates decreases if the colony queen is removed, such that they do not recognize conspecific non-nestmates as different. Here we tested the hypothesis that the presence of the colony queen influences the concentration of octopamine, a neuromodulator, in worker ants, which in turn has an effect on nestmate recognition acuity in workers. We demonstrate that queenless workers exhibit reduced brain octopamine levels and reduced discriminatory acuteness; however, feeding QL workers octopamine restored both. This is the first demonstration of a link between the presence of the colony queen, a worker biogenic amine, and conspecific nestmate recognition, a powerful expression of colony cohesion and territoriality.