Image by Katja Schulz/Flickr
Deep in the jungle, an ant begins to act strangely. It walks away from its colony and up a tree, biting down on a leaf’s vein. The ant stays there until it dies. And nothing happens for a while, but then a fungus sprouts out of the base of its head. Long and thin, the fungus grows into a macabre leash. Once it’s good and ready, the fungus rains spores down onto ants below, infecting them. And so the cycle of zombie ants continues.
The one where the ant gets turned into a zombie
If this were a movie, we’d jump back to the beginning of the story: we’d see a spore growing vertically out of the ground, waiting until it catches on an ant that just happens to be walking by. Then it blows a hole in the ant’s exoskeleton. Using enzymes and a lot of pressure, the fungus breaks into the ant, kind of like a safe-breaking team in a heist movie.
The fungus is called Ophiocordyceps; it’s a parasite that uses zombie ants to do its bidding. At this point, the fungus is branching out inside the ant, using its string-like hyphae. It becomes a network within the insect, feeding off its host. The ant has no closed circulatory system, so its fluids sort of slosh about in its body. This makes it easy for the fungus to get around.
Ophiocordyceps makes its way to the ant’s brain but then stops. The fungus encircles the brain but doesn’t interfere with it. There’s more important business elsewhere. And besides, the brain must be intact to ensure the ant can still function. Moving on, the fungus breaks into the ant’s muscle cells.
For three weeks, the fungus grows inside the ant. Its victim acts normally and no one suspects a thing. Normally, ants quickly remove sick individuals from their colony because one infected ant threatens the entire family. In a way, the ants act like an immune system for the colony as a whole. But Ophiocordyceps gets around this. It doesn’t change the ant’s behavior or smell — at first. Once the ant is out of sight from its colony, the horror begins.
The fungus takes control of the ant’s muscles, moving its puppet jerkily up a tree. By stopping the flow of calcium between the muscle cells, the fungus has essentially given the ant a case of rigor mortis. Ophiocordyceps has created a zombie ant minion.
Finally, the zombie ant bites down on a leaf (or a twig, depending on where this is happening) and dies six hours later.
Parasitic mind control isn’t just for the movies
While the “mind-control” technique appears to actually be muscle manipulation, Ophiocordyceps may be affecting the ants’ brains after all. The parasitic fungus is very closely related to another fungus — the one used to make the hallucinogenic drug LSD. When scientists dissected parasitized ant brains, they found tons of alkaloids inside. These are organic compounds that have various effects on animals and humans. For example, morphine and nicotine are both alkaloids. The opium poppy and the ergot fungus (the one LSD was made from) both have about 30 different alkaloid kinds in them. However, it’s unclear what the alkaloids are doing in the ant brains. The fungus appears to be heavily drugging its ant victims.
As miraculous of a story this is, it isn’t the only case of mind control in the animal kingdom. There are parasitoid wasps that command spiders to make webs for their young, barnacles that turn crabs into barren barnacle nannies, and worms that force crickets to drown themselves. It’s a ruthless world out there.