Flies fight off parasites by consuming alcohol

17 February 2012


Fruit flies that fall victim to parasitic wasps turn to alcohol to fight off the infection, recent research has revealed. Fruit flies, or drosophila as they are known scientifically, are often exposed to relatively high concentrations of dietary alcohol produced by the natural fermentation of sugars in the rotting fruit that forms their food staple.

In fact the creatures are attracted to the scent of alcohol since it indicates a likely meal, which is why they frequently flock to an open bottle or glass of wine. But this same smell also attracts a different beast entirely - a species of parasitic wasp that lays its eggs inside the fly larvae where they hatch and devour the insect from the inside out.

Remarkably, however, the drosophila can detect when they've become a victim of these bodysnatching wasps and up their alcohol intake accordingly. This, in turn, triggers the insect equivalent of foetal alcohol syndrome in the developing wasp, destroying it.

Alcoholic fliesThe discovery, published in Current Biology, was made by Emory University scientist Neil Milan and his colleagues. Compared with controls that tend to avoid alcohol-containing foodstuffs, fly larvae infected with wasp parasites, they found, when offered a choice between food containing 5% alcohol or food containing no alcohol, preferentially picked the boozy food. And the larvae also wandered between the two food sources to achieve the right level of alcohol in their bodies to poison the wasps without harming themselves. According to the researchers, this is the first time that such "self medication" using alcohol to treat an infectious illness has been observed.

Even more intriguingly, as they point out in their paper, "Although many studies in humans have documented decreased immune function in chronic consumers of alcohol, little attempt has been made to assay and beneficial effect of acute of moderate alcohol use on parasite mortality or overall host fitness following infection." So maybe the age-old argument that the occasional tipple is "medicinal" is perfectly valid after all!


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