Zombie Ant Fungus Knows the Brains of its Insect Hosts

A parasitic "zombie" fungus may only be able to target one specific type of ant. Scientists have found that this fungus, which can manipulate the behavior of ants, only emits its cocktail of behavior-controlling chemicals when encountering the brain of its natural target host.

"Fungi are well known for their ability to secrete chemicals that affect their environment," said Charissa de Bekker, lead author of the new study, in a news release. "So we wanted to know what chemicals are employed to control so precisely the behavior of ants."

The "zombie" fungus causes host ants to journey to a location near an ant nest. Then, it causes the ant to bite onto a plant before dying. The fungus then emerges from the corpse of the ant and releases its spores to infect more hosts.

In this case, the researchers examined a fungus species that normally controls an ant species in the genus Camponotus. In order to test whether the fungus could control other ant species, they infected non-target hosts from the same ant genus and another genus, Formica. While the fungus was able to infect and kill non-target ants, though, it couldn't manipulate their behavior.

Intrigued by this, the scientists removed ant brains and kept the organs alive in special media. The researchers then grew the fungus in the presence of brains from different ant species in order to determine what chemicals it produced for each brain.

"We could see in the data that the fungus behaved differently in the presence of the ant brain it had co-evolved with," said de Bekker. "There is no single compound that is produced that results in the exquisite control of ant behavior we observe. Rather, it is a mixture of different chemicals that we assume act in synergy."

In fact, the scientists found thousands of unique chemicals, most of them completely unknown. In addition, they found two known neuromodulators, guanobutyric acid (GBA) and sphingosine, which have both been reported to be involved in neurological disorders.

"This is one of the most complex examples of parasites controlling animal behavior because it is a microbe controlling an animal-the one without the brain controls the one with the brain," said David Hughes, co-author of the new study. "By employing metabolomics and controlled laboratory infections, we can now begin to understand how the fungi pull off this impressive trick."

The findings are published in the journal BMC Evolutionary Biology.