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Don't bug me: Japan team finds brain mechanism behind female fruit flies' romantic decisions

This illustration shows a female fly judging a potential male mate while repeatedly refusing his advances. (Mainichi)

NAGOYA -- A Nagoya University research team has discovered the brain mechanism in female fruit flies behind the decision to accept the advances of male fruit fly lonely-hearts, even if she has rejected those advances repeatedly before.

"The existence of this brain mechanism shows that to mate, it's important for the male to continue courting even if the female has turned him down many times," the team concluded. Among living creatures which have courtship behavior, the female often refuses a male many times before accepting him as an adequate mate.

The team, led by neuroscience professor Azusa Kamikouchi, identified a neural network for making mating decisions that switches the female fly's intentions from "refuse" to "accept." The network consists of two bunches of neurons. One reacts to the dopamine released by contact with a courting male by issuing rejection orders. This phenomenon in turn activates the second group of neurons, pushing for acceptance as neurotransmitters are released that suppress the first group.

The research team also found that this network is located in a part of the insect's brain that is similar to the part of a human brain involved in forming social bonds and decision-making.

Team member Hiroshi Ishimoto explained, "The findings could be a clue to clarify the evolution of the female brain, which has developed a behavior of carefully judging a potential partner after first refusing him. The fruit fly has many neural mechanisms which are common among animals in general, so the findings should lead to the clarification of human brain mechanisms as well, including for forming social bonds."

(Japanese original by Takayo Hosokawa, Nagoya News Center)

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