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Title: Isolation of a pyrazine alarm pheromone component from the fire ant, Solenopsis invicta

Author
item Vander Meer, Robert - Bob
item Preston, Catherine
item Choi, Man-Yeon

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2009
Publication Date: 2/10/2010
Citation: Vander Meer, R.K., Preston, C.A., Choi, M.Y. 2010. Isolation of a pyrazine alarm pheromone component from the fire ant, Solenopsis invicta. Journal of Chemical Ecology. 36:163-170.

Interpretive Summary: Social insects maintain colony integrity and sociality largely through complex pheromone (chemical) interactions. One pheromone, the alarm pheromone, acts to put other colony members in a state of heightened alertness. In ants alarm pheromones were among the first chemical ecology examples, primarily due to the large amount of pheromone produced. The fire ant is at the top of the list of the world’s worst invasive ant species, causing billions of dollars in costs each year for damage repair and control. The fire ant alarm pheromone may provide opportunities for development of novel biologically-based fire ant control methods. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida, isolated and identified 2-ethyl-3,6-dimethylpyrazine as an alarm pheromone component of the fire ant, Solenopsis invicta. The compound is produced in the mandibular glands of male and female sexuals, and worker fire ants. Workers produce very little of the pyrazine, but respond to it at extremely low concentrations. This is the first report of 2-ethyl-3,6-dimethylpyrazine from a Solenopsis species and the first report of this alkaloid functioning as an alarm pheromone. The synthetic pyrazine alarm pheromone could lead to novel control methods for this invasive pest ant through disruption of normal fire ant activities, including mating flights.

Technical Abstract: Alarm pheromones in social insects are an essential part of a complex of pheromone interactions that contribute to the maintenance of colony integrity and sociality. The alarm pheromones of ants were among the first chemical ecology examples, primarily due to the large amount of pheromone produced and a distinct bioassay. However, the alarm pheromone of the fire ant, Solenopsis invicta, has eluded identification for over four decades, until this report. We have identified 2-ethyl-3,6-dimethylpyrazine as an alarm pheromone component for S. invicta that is detected by worker ants at 30pg/cm3, which is comparable to alarm pheromone sensitivities reported for other ant species. The source of this alarm pheromone are the mandibular glands, which in fire ants are not well developed and contains only ca. 300pg of the pyrazine - significantly less than the microgram quantities of alarm pheromones reported for several other ant species. The pyrazine is produced by female and male sexuals, and workers, which suggest that it may be involved in fire ant mating flight initiation, as well as the typical worker alarm response. This is the first report of 2-ethyl-3,6-dimethylpyrazine from a Solenopsis species and the first report of this alkaloid functioning as an alarm pheromone.