Past Experience Of Pheromones Induces Dominant Courtship Behavior In Fruit Flies

The work is reported by Jean-Francois Ferveur and colleagues at theUniversite de Bourgogne, France, and the University of Manchester,United Kingdom.

When an adult male fruit fly encounters a young male fly, hewill actively court the younger individual, sometimes becomingaggressive. These young males that have encountered older flies will goon to similarly dominate other adult males that had encountered onlyyoung flies--something in the early experience of the "dominant" fliesmakes them more aggressive. In the new work, researchers investigatedexactly what it is about past experience of these flies that influencesadult behavior. Clues caused the researchers to suspect that a key rolewas played by a chemical signal--a pheromone--carried by adult malesduring the early encounter.

To prove this, the researches used mutant flies that lack thenormal adult pheromones, and they covered these pheromone-defectiveflies with a variety of other smells. The researchers were able todemonstrate that a male shows courtship dominance behavior over youngmales if he has been exposed to the smell of normal adult males duringa critical period in his life--the first 24 hours. In fact, anencounter with a single adult male was sufficient to make males exhibitdominance behavior when they reached adulthood. The researchers foundthat, intriguingly, it was not enough for young males to smell thesepheromones--the pheromones had to be carried by active adult males. Theeffect was so strong that males carried on exhibiting courtshipdominance behavior until they were five days old.

The authors of the study note that similar findings have beenreported in mice and hamsters, suggesting that dominance behavior mayoften be affected by chemical signals. In future studies, theresearchers hope to take the next step in understanding how dominancebehavior develops and thereby to identify which parts of the fly'sbrain are involved in processing dominance-inducing signals.

The researchers included Nicolas Svetec and Jean-François Ferveur of the Université de Bourgogne in Dijon, France; and Matthew Cobb of the University of Manchester, Manchester, UK.

Svetec et al.: "Chemical stimuli induce courtship dominance inDrosophila." Publishing in Current Biology Vol 15 No 19, pages R790-792www.current-biology.com