Ant-Doctor will not be the sequel to this summer's blockbuster from Marvel Studios, but you can catch the next best thing crawling across the ground throughout much of Europe.
Scientists studying an ant species called Formica fusca offered the insects a choice between a pure honey solution and a honey solution spiked with toxic hydrogen peroxide. They found that ants afflicted by a fungal infection tended to opt for the hydrogen peroxide solution, whereas healthy ants were more likely to avoid it. This shift in preference suggests that the ants recognize that hydrogen peroxide helps fight off fungal infections and that its noxious effects become worth the risk when an ant falls ill.
"It is not known yet how ants know they are infected, but it's very clear that they do somehow change their behavior once they are," researcher Nick Bos told New Scientist.
Humans commonly use hydrogen peroxide that comes in an opaque brown bottle as an antiseptic for minor wounds. It's effective for this purpose because it's a source of reactive oxygen species, chemicals that are toxic to our own bodies as well as to invaders. These chemicals are found naturally in aphids and dead ants, which could provide a source of reactive oxygen species for sick ants in the wild.
To demonstrate that these ant doctors aren't quacks, Bos and his colleagues first demonstrated that hydrogen peroxide is an effective treatment for ants infected with the fungus Beauveria bassiana. On the pure honey solution, infected ants experienced a mortality rate of 60 percent, but that rate dropped to 45 percent when given the hydrogen peroxide-spiked solution. Healthy ants, in contrast, experienced a jump in mortality rate from five to 20 percent when fed the hydrogen peroxide solution.
The ants even appear to have a sense of the proper dose for treating infections. When offered a solution that had only a low concentration of hydrogen peroxide, infected ants typically chose to eat equal amounts of the toxic food and the pure food. Offering a stronger hydrogen peroxide solution caused the infected ants to change the balance, eating only half as much of the toxic solution as they did of the pure solution.
Taken together, these results suggest that ants have weighed the risks and potential benefits of ingesting reactive oxygen species remarkably precisely. They're also not the only insects out there self-medicating — scientists at Queen Mary University of London recently showed that bumblebees seem to do it, too.
Via: New Scientist
