Male fruit flies love to ejaculate – and they'll turn to booze if they can't

The team behind the research believes the findings could help to understand the biology of addiction.

Male fruit flies like to ejaculate and may turn to alcohol in absence of sexual reward, new research has found.

Scientists based in Israel found that sex – more specifically ejaculation – is an enjoyable experience for the flies (Drosophila melanogaster).

Galit Shohat-Ophir, of Bar-Ilan University in Israel, said: “Successful mating is naturally rewarding to male flies and increases the levels of a small peptide in the brain called Neuropeptide F.

“Male flies that are sexually deprived have increased motivation to consume alcohol as an alternative reward.”

The study is based on previous research from 2012, where the team found that male fruit flies opted for booze after being rejected by female partners.

The scientists believe their findings could help understand the biology of addiction.

Mr Shohat-Ophir said: “The principles by which the brain processes reward are extremely conserved in all animals; this is a really basic every day machinery that helps animals survive.

“Drugs of abuse use the same systems in the brain that are used to process natural rewards.

“This allows us to use simple model organisms to study aspects of drug addiction, including the interplay between natural and drug rewards and the connection between experience and the mechanisms that underlie the risk to develop drug addiction.”

To understand how the mechanism worked, the researchers looked at neuropeptide corazonin (CRZ) nerve cells in the abdomen – which cause sperm release and an increase of neuropeptide F in flies.

Some male fruit flies were then genetically engineered to ejaculate when exposed to a red light that activated the CRZ neurons.

Drink-drive survey
The researchers found male fruit flies turned to alcohol when deprived of sexual reward (Philip Toscano/PA)

Experiments showed the flies displayed a strong preference for the red light, implying that ejaculation in itself is a rewarding experience.

After several days of being exposed to the light, the insects tended to prefer non-alcoholic drink over one spiked with ethanol.

The flies had high levels of neuropeptide F in their brains, similar to males that actually mated with female partners, the researchers said.

But males – both control and engineered flies – who were not exposed to the red light (meaning they did not ejaculate) went for the boozier drink.

According to the researchers, their work “adds to evidence that manipulating sexual experience in flies affects their interest in consuming alcohol”.

The research is published in the journal Current Biology.

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