Courting both ways

Doped-up male fruit flies fancy other males

Boost the dopamine in a male fruit fly’s brain, and he’ll see guy flies in a whole new way.

Given a choice, these high-dopamine fellows still prefer a virgin female fly to a male, says Jean-François Ferveur of the University of Burgundy in Dijon, France. But given only a male, the fruit flies with the altered brain chemistry will court him. Male fruit flies from the wild do so only rarely, Ferveur and colleagues from China report in the May 21 Journal of Neuroscience.

Flies genetically engineered to crank up dopamine concentrations in their nervous systems or just given dopamine-enhancing drugs still make the usual romantic gestures, the researchers say. A courting male flirts with his wings, extending one hopefully or vibrating them in a serenade. He taps his intended, and if all is going well, licks her. Or him.

In all-male groups enhanced for dopamine, courting males focus attention on males that were already occupied with another male. At times multiple males form chains, sometimes closing into rings. “It’s very spectacular,” Ferveur says, but raises the question of whether the effect comes from the courter or the courted.

To sort out the effect, researchers offered high-dopamine males a potential male partner that wasn’t going to do much come-hither luring because he’d had his head removed. “Decapitated fruit flies can live for days,” Ferveur says. They still smell male, and they walk, jump and groom, but they don’t serenade. Even such low-key partners attracted attention from the high-dopamine courters.

Enhanced males still had their normal senses about them; they still responded as usual to offerings of sugar and other olfactory and gustatory tests. So Ferveur argues that the alteration is not about receiving distorted information to begin with. Instead, he says, it’s about what the brain does with information.

Studying same-sex courtship in fruit flies offers a way to explore the brain chemistry underlying loss of inhibition, says Kyung-An Han of Penn State University in University Park. She and her colleagues have shown that chronic drinkers among male fruit flies, those given ethanol repeatedly by researchers, also start courting other males. “Alcohol is a dirty drug” in that it affects a lot of physiological processes, Han says. The new paper indicates that dopamine by itself can produce the reaction.

Susan Milius

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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