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What makes a fruit fly sing
July/August 2008
by Carole Bass '83, '97MSL
In the fruit fly world, only the boys sing love
songs. But postdoctoral researcher J. Dylan Clyne has discovered that, with
help, the girls can make music, too. They just have to lose their heads.
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In fruit flies, the song neurons are located not in the head but the thorax.
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Clyne, a physiology fellow at the School of Medicine,
and his Yale mentor, Gero Miesenbock (now at Oxford), suspected that the song
circuit is present in females but lies dormant. Using a technique developed by
Miesenbock, the pair used lasers to stimulate the neurons they guessed were
controlling singing in males.
The results were encouraging, but not definitive
enough. So the researchers tried decapitation.
This seems extreme, but it makes biological sense. In
fruit flies, the song neurons are located not in the head but the thorax. The
head contains command centers, Clyne explains, which control not only singing
but other behaviors that could interfere with mating. "When you cut off the
head, you're eliminating the command neurons," he says. "That increases the
mating behavior."
When the researchers tried activating the neurons in
decapitated females, the technique worked beautifully. (The flies make songs by
vibrating one wing -- actually more like fiddling than singing.) "The female song
has a slightly different tune," Clyne notes. "But the surprising thing is that
they sing at all."
The findings, reported in the April 18 issue of Cell, show that "you don't need large
sex differences in the brain to get large differences in behavior," Clyne says.
"There seems to be a switch that's turned on in the males and off in the
females."
That observation supports the notion that, in flies
and in other species, "the neural system is more or less unisex, and then you
have these different modules" that control behavior, he says. "From an
engineering standpoint, it's a lot easier to give both sexes the same circuitry
and just turn the switch off or on."
Clyne's next ambition: "Try to figure out where those
switches are." 
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