Could the cordyceps ant fungus really cause a zombie apocalypse?
This animation shows the harmless fungus Phycomyces (not the zombie art fungus Cordyceps!) growing fruiting bodies, by Natasha Mutch, SayoStudio.
Cordyceps… it’s been all the rage ever since the release of HBO’s The Last of Us release. Prior to the show’s inception, The Last of Us video games gave audiences a unique twist on the ‘zombie apocalypse’ trope. Based on a real-world phenomenon, the fungus Ophiocordyceps, or what we’ll call ‘zombie ant fungus’ has now mutated to survive a warming planet; jumping from ants to humans as its host species. While The Last of Us show and games may seem much more thrilling to folks looking for a scare; the real Ophiocordyceps fungus doesn’t need any embellishment to scare your pants off.
Fungal Infections
But first, we need a baseline understanding of what fungus actually is. Fungi exist everywhere. We interact with fungus frequently (i.e. moldy bread or fruit, anyone?) but for the most part, it’s relatively benign for us. You can read more about the peach fungus featured here in our art gallery. There are indeed fungal infections humans do need to worry about, however. One example is the common fungal infections called ‘Athlete’s foot,’ which ranges from annoying for healthy people to deadly for immunocompromised individuals. Candida auris, a multi drug resistant fungus, is the scariest one to date; and is of high concern to WHO and the CDC. Spreading like wildfire in hospitals or nursing homes; C. auris clocks in at a 30-60% mortality rate in the U.S. alone.
Honestly, that seems scary enough to most of us, but ants seem to hold the winning category of Scariest Fungal Infection Ever (in case it were a contest…).
Zombie Fungus: Ophiocordyceps
Ophiocordyceps unilateralis has evolved in concert with its host for at least 48 MILLION years. We know this thanks to a fossil leaf found in 2010, which is uniquely scarred in a fashion that can only be attributed to ant ‘death grips’ (and no, that’s not a cool new metal band name.) A ‘death grip’ is a behavior that these zombie ants exhibit in the final stages of their cordyceps infection. The discovery of this parasitic relationship between this fungus and its host proves that this phenomenon is far more ancient than previously thought by researchers.
Once infected, the fungal cells invade the ant’s bloodstream and replicate. Ophiocordyceps begin to build tube-like connections, which transmit vital information and nutrients between each other. As their numbers grow within the ant’s body, they harvest nutrients to fuel even more networks, which function similarly to neurons.
Zombie Fungus: Mind Control
As the ant is slowly starved of vital nutrition, it’s believed (not yet proven) that the fungus secretes an array of chemicals tailored to take over the behavioral controls within the ant’s brain. The ant’s neurons die (researchers think) while the fungus begins pulling the strings of its muscle fibers, cutting off all control the ant has over its body. It’s even possible that specific neural receptors, like ones for dopamine or serotonin, might be hijacked by the fungus to control behavior.
Entering the final stage of infection, the ant begins to climb. The fungus needs just the right amount of humidity to help produce a fruiting body. After climbing just about 10” high, the infected host clamps onto the underside of a leaf. This ‘death-grip’ is the ant’s swan-song, as the fungus proceeds to use every last bit of energy to produce a large stem. That stem grows a fruiting body, which rains down spores onto the ant’s colony to reproduce and spread.
Do we need to worry about this fungus?
We hope that this wasn’t just pure nightmare fuel for our readers- who need not worry; cordyceps cannot exist in human bodies, which run far too hot. Hardcore The Last of Us fans might say, “Hey, they discussed this in the game! Global warming caused the fungus to mutate and leap to humans!” The zombie ant fungus is so very specifically evolved for insect hosts, as it’s taken millions of years to perfect that niche. So while we certainly don’t need to worry about zombie fungus at present, it’s a possibility that other fungi within our own bodies could change and evolve in the future. Current microbiome research advancements show that complex bacteria and fungus exist within our gut and sometimes dictate our cravings, moods, and actions. Perhaps it’s not so science fiction to look inward and study the fungus that do indeed live among us.
We have to admit, we’re fascinated by fungus. In the future, we’d like to highlight some of the amazing, beneficial impacts of fungus. We’re working on a piece about fungus and medicine, and another on fungus forest ecology. Let us know in the comments what science you’d like to learn more about and have us visualize it!