Drosophila's Drunk Defenses

Self-medication is natural, according to Dr. Schlenke at Emory University.

Although some people, and you may know a few, have mastered the art of drinking to get drunk. Some species actually drink alcohol to survive. One of these species happens to be the fruit fly, the most common of which is the Drosophila melanogaster.

Drosophila melanogaster
Photo credit: Aka

As tiny as fruit flies are, they serve as a host for parasitic wasps. These wasps lay their eggs in the larva of fruit flies. The wasps develop inside the living flies and feed on their tissues until eventually crawling out of their hosts -- this is why fruit flies drink. And I don't blame them.

Fruit fly larva graze on yeast and bacteria causing old fruit to rot. While breaking down sugar fruit fly fermentation can leave a brown banana with an alcohol content higher than your average bottle of beer. 

In a recent study called Alcohol Consumption as Self-Medication Against Blood-Borne Parasites in the Fruit Fly scientists tested the nature of this drunken defense in the lab. The scientists allowed the wasps to attack two types of fruit fly larva: the sober type and the drunk type.

In larva who were not permitted alcohol the parasitic wasps grew normally. However in larva who were allowed alcohol, 65% of the parasites suffered a brutal death and there was also about 60% less wasp eggs laid.

The wasps who were lucky enough to be laid in an alcoholic host ended up with their internal organs outside of their body. It seems their tolerance for alcohol is much lower than that of the fruit fly -- to the point where their guts shoot out of their anus. What was most interesting about this was that it only happened if the larva consumed alcohol after the wasps were already living inside them.

Noting this, researchers decided to test if the flies are smart enough to know that drinking can save their lives. Apparently they do. In test areas with alcoholic food and nonalcoholic food placed on different sides 30% of the larva indulged themselves in the free booze. However, in the same area with wasp infected larva, 80% sought release in drunkenness.

Over the years, scientists have gathered numerous examples of animals medicating themselves. But this study in particular is the first to show that animals actually use alcohol as medicine. The flies knew the wasps were infecting them and sought defense by drinking. In other words, they self-medicate by getting smashed.

When it comes to humans, we have no idea whether a heavy drinking binge has any effect on internal parasites, no one’s ever tested whether humans can consciously battle bloodborne pathogens by getting their blood alcohol levels up. But that doesn't mean you can't try! Cheers!