Male Fruit Flies Have Method for Dealing with Rejection

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The courtship ritual of the lowly male fruit fly is far more elaborate than one might presume. It goes a little something like this:

First, the eager hopeful taps the female's body with his foreleg, partially to say, "Well hello, beautiful," but mostly to make sure that the lady fly he's pursuing is actually a lady. Next, the male rhythmically vibrates his wings, using them as instruments to play a sultry courtship song. If the female likes what she hears, she'll become more receptive to mating. After his sweet serenade, the male engages in a little foreplay, extending his proboscis -- a mouth appendage -- and licking the female's genitalia. Lastly, the male attempts to mount the female and initiate copulation.

If the male's attempt is successful, the lovemaking will last approximately 15 to 20 minutes. If not, the female will abruptly kick him to the curb (so to speak). At this point, according to a recent study, the spurned male fruit fly may turn to drinking. But in all likelihood, alcohol will not be readily available, so he will resiliently bounce back and continue on his quest to mate.

shutterstock_110050226.jpgNaive male fruit flies begin their reproductive pursuits courting both virgin and mated females, despite the latter being more unreceptive to mating. This often works out poorly, because males can waste a lot of time, energy, and libido on futile mating efforts with unreceptive females.

Luckily, males appear to have a neurological process for coping with and learning from rejection. It was recently uncovered by scientists at the Research Institute of Molecular Pathology in Vienna and reported in the journal Nature.

The process is fairly simple: Male fruit flies start their pursuit of a mate by being promiscuous, then grow more selective over time, the researchers say.

As mentioned earlier, male fruit flies begin by courting both virgin and already mated females, despite the latter being less inclined to mate. But after numerous rejections, males learn to identify mated females and thus concentrate their reproductive efforts on virgin females. Attempts are more infrequent, but success rates vastly increase.

Researchers gleaned the process by conducting assays that paired male fruit flies with both virgin and mated females. They found that males that had been rejected by mated females less actively pursued mated females compared to virgins. Further testing revealed that this new selectiveness stemmed from males becoming more apt at recognizing cVA, a male-specific pheromone that is transferred to the female's cuticle upon mating.

Seeking to uncover the hormone and signaling pathways involved in male flies' improved ability to recognize cVA, the researchers carried out numerous experiments designed to narrow down the neurons and genetic receptors involved. Using previous research as a guide, they targeted neurons and genes involved in the dopaminergic pathway, which is associated with learning and responsible for transmitting dopamine. They then whittled down the suspects by suppressing and activating them in a controlled fashion and monitoring how the changes affected flies' ability to learn to detect cVA.

After carrying out their experiments, the researchers proposed that a failed mating attempt causes dopamine neurons to convey a learning signal via the DopR1 receptor, which induces the changes in cVa detection.

"Our work... reveals critical behavioral, cellular and molecular components of the learning rule by which Drosophila adjusts its innate mating strategy according to experience," the researchers said.

In other words, a relatively simple learning circuit helps male fruit flies learn from rejection, thus greatly aiding their quest to find that special female.

(Image: Fruit Flies via Shutterstock)


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