Rejected fruit flies turn to booze


Before you swat that little fruit fly landing on your apple, be aware that he may share at least one thing in common with humans. He might react to rejection by a female by turning to alcohol.


A recent study from a Howard Hughes Medical Institute research centre found that male fruit flies drink more alcohol when a female denies them sex. Their luckier male friends who successfully have sex show significantly less desire to chug ethanol.


The experiment sounds relatively simple. The scientists exposed male fruit flies to two different types of female fruit flies. One set of females were virgins, and the males had plenty of them to mate with. The other set of females had already mated.

Once female fruit flies mate, they are not inclined to mate again very soon. When a male fruit fly mates with a female, he injects her with a sex peptide that affects her brain to no longer desire sex. This prevents her from mating with his competing male rivals.


When the new male fruit flies were exposed to this second set of females, they were rejected. This meant no sex, and no “reward” experience in the brain. Weward mechanisms are well documented in the insect and human brains. They respond to activities like sleeping, eating, and, yes, having sex. When this reward system in the fruit fly isn’t satisfied, scientists believe the fly “drowns its sorrows” the way we do: with a good, stiff drink.


The researchers connected the lack of sex with a decrease in a certain brain protein, neuropeptide F, in the rejected males’ brains.


When scientists exposed the sexually satisfied and unsatisfied males to a choice of ethanol-based and non-ethanol-based foods, the unsatisfied males went straight for the alcohol. It appeared to make up for their earlier lack of reward. The satisfied males showed no significant preference for the alcohol.


The scientists wondered whether or not manipulation of the receptors of the neuropeptide would change the flies’ behaviour. When scientists blocked the receptors in satisfied males, these males quickly turned to alcohol also. When scientists boosted the neuropeptide in unsatisfied males, their original desire for alcohol lessened.


Is this the same for humans? Scientists say it’s still too early to tell, but it looks promising.


Past research shows human males also turn to alcohol when they’ve been rejected by a female. Studies have also found similarities between neuropeptide F in fruit flies and a human neuropeptide, neuropeptide Y. Neuropeptide Y has already been linked to depression and post-traumatic stress disorder.


If scientists successfully manipulate the brains of fruit flies to bring alcoholism under control, they may be able to eventually do this with humans as well. This could lead to a breakthrough in the treatment of alcoholism and in understanding addictions in general.


So if you ever see a fruit fly land on your Smirnoff, know that he probably just had a really bad beating to his ego, and a rotten banana just wouldn’t do.


P.S. This is my last Medium article at UTM. I have loved every minute of writing for our university, and I hope anyone who has enjoyed my articles would like to contribute to the science topics in our newspaper in the future.