Zombie Fungus – How it takes over ant bodies to control their minds
To find the world’s most sinister examples of mind control, don’t look to science fiction. Instead, go to a tropical country like Brazil, and venture deep into the jungle. Find a leaf that’s hanging almost exactly 25 centimeters above the forest floor, no more and no less. Now look underneath it. If you’re in luck, you might find an ant clinging to the leaf’s central vein, jaws clamped tight for dear life. But this ant’s life is already over. And its body belongs to Ophiocordyceps unilateralis, the zombie-ant fungus.
The fungus’s skill at colonizing ants is surpassed only by its skill at colonizing popular culture. It’s the organism behind the monsters of the video game “The Last of Us” and the zombies of the book The Girl With All the Gifts. It’s also an obsession of one David Hughes, an entomologist at Pennsylvania State University, who has been studying it for years. He wants to know exactly how this puppet master controls its puppets—and his latest experiments suggest that it’s even more ghoulish than it first appears.
Hughes’s student Maridel Fredericksen used a special microscope to julienne infected ants into slices that were just 30 microns thick—the width of an extremely fine human hair. She scanned each slice, compiled the images into a three-dimensional model, and painstakingly annotated which bits were ant and which bits were fungus. It took three months to mark up just one muscle. To speed things up, Hughes teamed up with computer scientist Danny Chen, who trained an artificial intelligence to distinguish ant from fungus.
But surprisingly, they can do that without ever physically touching the brain itself. Hughes’s team found that fungal cells infiltrate the ant’s entire body, including its head, but they leave its brain untouched. There are other parasites that manipulate their hosts without destroying their brains, says Kelly Weinersmithfrom Rice University. For example, one flatworm forms a carpet-like layer over the brain of the California killifish, leaving the brain intact while forcing the fish to behave erratically and draw the attention of birds—the flatworm’s next host. “But manipulation of ants by Ophiocordyceps is so exquisitely precise that it is perhaps surprising that the fungus doesn’t invade the brain of its host,” Weinersmith says.
In retrospect, that makes sense. “If such parasites were merely invading and destroying neuronal tissue, I don’t think the manipulated behaviors that we observe would be as compelling as they are,” says Charissa de Bekker from the University of Central Florida. “Something much more intricate must be going on.” She notes that the fungus secretes a wide range of chemicals that could influence the brain from afar.
So what we have here is a hostile takeover of a uniquely malevolent kind. Enemy forces invading a host’s body and using that body like a walkie-talkie to communicate with each other and influence the brain from afar. Hughes thinks the fungus might also exert more direct control over the ant’s muscles, literally controlling them “as a puppeteer controls as a marionette doll.” Once an infection is underway, he says, the neurons in the ant’s body—the ones that give its brain control over its muscles—start to die. Hughes suspects that the fungus takes over. It effectively cuts the ant’s limbs off from its brain and inserts itself in place, releasing chemicals that force the muscles there to contract. If this is right, then the ant ends its life as a prisoner in its own body. Its brain is still in the driver’s seat, but the fungus has the wheel.
A carpenter ant infected with a brain-controlling zombie fungus