Hair of the bug
Robert Treasure discusses how fruit flies use alcohol as a defensive tactic
I’m sure I’m not alone in my scepticism of the apparent healing properties of alcohol when suffering from a cold or general post-Saturday-night divine punishment. Yet the latest research conducted at Emory University, Atlanta, suggests that fruit flies genuinely use alcohol to combat infection – from parasitic wasps.
As you may well have inferred from their imaginative name, fruit flies (Drosophila melanogaster) eat rotten fruit, or more accurately, the yeast that decays said fruit. As by-products of the decaying process, yeast produces carbon dioxide and ethanol, thus rendering the fruit slightly alcoholic. Subsequently, the fruit fly has evolved resistance to the harmful effects of alcohol (in the form of the enzyme alcohol dehydrogenase), an adaptation not exhibited by the parasitic wasps (Leptopilina boulardi and Leptopilina heterotoma) that deposit their eggs in its circulatory system.
This disparity in ethanol resistance prompted Todd Schlenke and his colleagues to feed healthy and parasited fruit flies in an environment containing untreated and alcohol-coated fruit, the latter ranging in concentration from that of medium strength lager to Special Brew (4-10%). They observed that the parasitised flies overwhelmingly preferred the alcoholic to the regular fruit (80 to 20% respectively), whereas only thirty percent of healthy flies were equally enticed. These numbers show a conscious decision on behalf of the parasitised flies to actively seek out the alcoholic fruit in a bid to remedy their infection. This proved to be an excellent tactic: the degree of oviposition (egg laying) by the wasps in these flies was reduced greatly by the presence of ethanol, Schlenke explains why:
“The wasps die [from ethanol exposure] and all of their organs are diverted through their anus. Their guts actually pop out..”
Apologies to anyone eating their lunch for the vivid mental image painted by Schlenke, but it’s clear that it is in the wasps’ best interests to steer clear of the ethanol-inducing flies. Schlenke also goes on to state that the investigation documents the first evidence that alcohol consumption can act as a defensive mechanism against infectious diseases and parasites, but before you hit the bottle to cure your ailments remember that the fruit fly’s alcohol tolerance is the result of millions of years of evolution in an ethanol-rich environment, not consecutive nights in the student union.
