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Wednesday, September 22, 2021

Column: Zombie ants

Zombies are real. Forget virus zombies or voodoo zombies – actual insect zombies roam the rainforests.

A genus of fungi called cordyceps sends spores into the air and infects oblivious invertebrates like ants and grasshoppers. Cordyceps eventually kills the insect host and sends a stalk that releases spores out of the cadaver. It’s the circle of fungal life.

The scary thing about cordyceps, though, is the insects turn into zombies before they die.

Cordyceps takes over the infected insect’s brain. Somehow, the fungus tells the insect’s brain climb, climb, climb because sending spores out from a greater height increases dispersion. Spores are carried on the wind, and air circulation increases higher up.

I’ve watched a lot of zombie movies lately, so I’m impressed with the healthy ants’ reactions to the zombies. Ants will find the infected individual and carry it far away from the colony. The ants aren’t smart enough to know how cordyceps works, but their instincts tell them to get the diseased ants as far away as possible. Our instincts tell us to blast zombies with shotguns, but ants take their still-alive, twitching zombie friends into the wilderness to die.

A whole colony of ants can be infected by the spores. The cordyceps fungi are so specialized scientists think each species of cordyceps is unique to one species of insect. The BBC show “Planet Earth” has a segment about cordyceps (Youtube: cordyceps). Chilling violin music plays as time-lapse photography shows a thin green tentacle of fungus rising from an ant’s head. Maybe I’ve watched too much sci-fi, but now I imagine a cordyceps that emerges alien-like from humans.

I interviewed Dr. Tom Gordon, chair of the UC Davis plant pathology department, about cordyceps. I’d first heard about cordyceps and their mind-control powers in Gordon’s SAS 30 class, “Mushrooms, Mold and Society.” Gordon said the ability to get infected hosts to climb is the reason cordyceps survives.

“There has been selection over time for [fungal] strains that influence that behavior,” Gordon said.

Cordyceps don’t infect humans. The high human body temperature and our protective layer of skin makes fungal infections of humans pretty rare. Humans can get toenail fungus and infections like ringworm (a fungus, not a worm), but fungi have a hard time breaching the skin barrier. There is no fungus that forces us to climb the Empire State Building.

There are fungi that can kill us, but some humans have decided to embrace the mind-altering powers of fungi.

Gordon, like many other researchers, thinks the hallucinogenic properties of some mushroom species were originally meant to control insect minds. Humans have bigger, much more complex minds than little ant ganglion brains, so fungal chemicals affect us differently.

Fondness for special kinds of mushrooms entered the college student scene during the psychedelic era, but use of “magic mushrooms” to obtain visions goes back centuries. In Siberia and Mexico, hallucinogenic mushrooms were used for religious visions and in healing ceremonies. Gordon says these traditional uses have been “contaminated by popular culture” as people were introduced to the hallucinogens in the context of recreation. The scene that pops into my mind is Paul Rudd and Seth Rogen watching Cirque du Soleil on shrooms in Knocked Up.

Will I ever have to worry about becoming a human fungal zombie? It’s unlikely, but I’ll keep the shotgun loaded.

MADELINE MCCURRY-SCHMIDT has a cow catcher welded to her pickup truck and a map to the nearest shopping mall taped to the dash. If you want help surviving the zombie apocalypse, e-mail her at memschmidt@ucdavis.edu.

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