'Zombie fungus' lives among us and not just as HBO plot of 'The Last of Us'
The HBO series "The Last of Us" premiered on Jan. 15, and was watched by 4.7 million viewers – one of the largest HBO debuts ever. Its storyline is a grisly one. A naturally occurring fungus known as Cordyceps mutates and leaps from its insect hosts to humans. The end result: an apocalyptic landscape populated by human zombies. The series is based on the 2013 video game of the same name.
Ah, but television is the stuff of fantasies and fiction, fortunately. Not so fast! Cordyceps fungi and its allies are quite real and all around us. Upon encountering a zombified insect or spider victim of the deadly fungus, which happens nearly every year – sometimes multiple times - my colleagues and I have often joked about what might happen if it ever crossed over to people.
Now we know, or at least we can vividly imagine our fate thanks to Craig Mazin and Neil Druckmann’s cleverly written and creative HBO series.
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Not-so-lucky crickets
Cordyceps (and closely related Ophiocordyceps) fungi have been known for well over three centuries and was first discovered in China. The latter group is well known for infecting ants. In our neck of the woods, I mostly see Orthopteran victims, especially the Carolina leafroller cricket.
Carolina leafroller crickets are common but shy and retiring. During the day, they hide in leaves that they roll up to form a bivouac. The cricket – distinguished by exceptionally long antennae – emerges under cover of darkness to forage.
Airborne spores of Cordyceps that fall upon a cricket enter its body and commence growing via long strands known as mycelia. The mycelia worm their way through the cricket’s innards, feeding on tissues but not killing its host, at least quickly. As a critical fungal mass develops, the Cordyceps moves to the head of the cricket and somehow rewires its behavior.
In a horrific last hurrah, the fungal parasitoid forces its victim to climb to a prominent perch in a tree or shrub, causes it to clamp down tightly on leaf, and kills it. The fungus, which has mostly consumed the cricket’s inner workings by this point, prepares to reproduce. Stem-like spikes called stroma shoot from the insect’s body; these are capped by perithecia, or fruiting bodies.
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The accompanying photo shows a Carolina leafroller cricket completely zombified, eyes dead and white, bristling with fruiting bodies. The perithecia soon rupture, releasing scads of windborne spores, hence the reason for the fungal reprogramming of the victim: to force it into a breezier location for successful spore dispersal.
Cordyceps does not confine itself to crickets. I have seen caterpillars, flies, moths and spiders that have succumbed to it.
What about humans?
We can thank our lucky stars that Cordyceps “zombie fungus” does not invade Homo sapiens, at least yet. If it ever does make the leap, at least some of us are in for a rough ride. As webs of fungal mycelia consume the victim, their behavior would become increasingly erratic and antisocial, yet they would still appear “normal."
As a grand finale, the infected person would be forced to climb a flagpole or some such tall object and seize the top with an unbreakable death grip. The Cordyceps flag would be the grisly new banner, the human pennant bristling with spikes of fungal stroma like a macabre human porcupine, eyes dead and pearly. Clouds of spores would erupt into the wind, seeking other humans to further the fungus.
Hopefully, "The Last of Us" is not prescient, or we are in for a new world order ruled by fungi. And the takeover will not be a walk in the park.
Naturalist Jim McCormac writes a column for The Dispatch on the first, third and fifth Sundays of the month. He also writes about nature at www.jimmccormac.blogspot.com.
This article originally appeared on The Columbus Dispatch: Zombie fungus infects spiders and insects
