We humans take medicine when we're sick. As do our primate cousins. Chimps, for example, snack on a bitter African shrub to combat intestinal worms. But the habit extends even to invertebrates. Take fruit flies—which sip alcohol to ward off parasitic wasps. Or wood ants, which line their nests with antifungal, antibacterial tree sap. Now researchers in Finland report that ants there that have encountered a pathogenic fungus appear to fight the infection by eating foods high in free radicals. Those are molecules with a talent for causing cell damage, in this case, to the cells of the fungus. That's according to a study in the journal Evolution. [Nick Bos et al, Ants medicate to fight disease]

The researchers collected some 400 wild ants. They exposed some to the fungus, and left the rest alone. Then they offered up a sort of eggy custard—either plain, or laced with free radicals—in the form of hydrogen peroxide. Uninfected ants didn't want anything to do with the radical-rich food. Which makes sense.  

“Exactly, I mean we don't take painkillers on a daily basis, or we don't take antimicrobial agents on a daily basis. Because that would have really severe side effects on the organism." Dalial Freitak, an insect immunologist at the University of Helsinki. 

Sick ants, on the other hand, preferred the peroxide diet—even before developing a full-blown infection. And the medicine upped their odds of survival some 30 percent. "I would definitely go for it!"

As for free radicals in the wild? Dalial says ants might get them from the honeydew substance that aphids produce. Or decomposing corpses—another ant favorite. No word on whether they sometimes seek out antioxidants.

—Christopher Intagliata

[The above text is a transcript of this podcast.]