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The Rules of Attraction

Tinkering with pheromones turns fruit flies into indiscriminate lovers

In the popular imagination, pheromones equal irresistibility. Now a team of University of Toronto biologists are saying that sometimes the chemical messages may be more “beat it” than “hey baby”.

Joel Levine, from U of T’s Mississauga campus, and his team genetically engineered fruit flies, Drosophila melanogaster, to lack the cells that give off pheromones. When they put the mutant flies to the test, they discovered that females lacking pheromones were even more desirable than regular gals — and even males from other species pursued them. Then again, pheromone-free male fruit flies were also the object of male affections.

Replacing just one missing pheromone restored both the species barrier and gender identity. “Just by manipulating one pheromone you can completely change the way they behave,” Levine told Nature News. “Recognition of sex and species is not about the genes of the individual; it’s about these cues.”

The researchers propose that the default for fruit flies is to be exceedingly sexually attractive, and that certain pheromones superimpose identity upon that substrate. Female attractiveness in the fruit fly, they speculate, depends on a delicate interplay between signals that attract and those that repel. They reported their findings in the prestigious scientific journal, Nature.

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