If you are one of the millions who have tuned in to HBO’s new show, “The Last of Us”, you might have a new fear of fungus.
On the show (and in the video game it is based on), a fungus that makes humans into zombie-like creatures causes modern society to crumble.
That fungus – Ophiocordyceps unilateralis – exists in real life, though it turns ants into zombies rather than humans.
According research published in the Communicative and Integrative Biology journal in 2011, “Ophiocordyceps unilateralis… is a specialized parasite that infects, manipulates and kills formicine ants, predominantly in tropical forest ecosystems.”
A study published in the Nature journal in 2020 explained that “the parasitic fungus manipulates its ant victims to behave like ‘zombies,’ walking randomly and displaying convulsions that make them fall down, after which the ants climb up vegetation to bite the underside of leaves or twigs.”
“We suppose that the heavy armament ‘of choice’ is the stromatal plate (the sexual stage or teleomorph) produced laterally on a stalk or clava emerging from behind the head of the ant – the emblematic feature of the zombie- ant fungus – buried within the stroma are the flask-shaped, thick-walled ascomata producing sac-like structures called asci,” said authors of the 2011 research.
When fungus branches breach the exoskeleton of the insect, “avoiding the cellular and humoral defenses of the ant,” it grows inside “as free-living yeast cells,” they said. They believe it take “a matter of days” for the yeast to colonize and produce “the nerve toxins to alter the behavior of the ant causing it to climb and bite onto vegetation.”
Fungus will form outgrowths from the ant’s body orifices and joints to “further secure the ant to the substrate,” as the insect cadaver is “mummified,” researchers explained.
Although the ants are dead, the fungus continues to grow inside their bodies “and the fungus’s fruiting body sprouts from the back of the ant’s head,” authors of the 2020 research said. After one or two weeks, the fungus produces spores from the fruiting body inside the zombie ants and it ruptures, spreading spores on the forest floor.
“Each spore has the potential to infect other unfortunate ants, turning them into zombie ants that allow the fungus to continue to propagate,” said the study.
“The show [is] taking a more realistic approach to the story and the world,” writer and co-creator Neil Druckmann of “The Last of Us” told Polygon about the team’s decision to depict the fungus on the show as a mushroom network. “If we wanted to treat it realistically, and there are spores near, characters would wear gas masks all the time. Then we lose so much, which is maybe the most important part of the journey is what’s going on inside behind their eyes, in their soul, in their beings. For that logistical reason, we were like, Let’s find a different vector.”
Zombie-ant fungus is usually found in tropical forests and may also be found in warm-temperate forest systems.
Ophiocordyceps unilateralis is an example of how “parasites (or parasitoids) can indirectly affect the behavior and physiology of their hosts in ways fit only for science fiction,” said the authors of the 2020 study. These “behaviors are known as the extended phenotypes of these parasites and are parsimoniously explained as the capacity of parasites to express their genes to modify the host behavior. The parasite manipulation hypothesis suggests that specific behavioral modifications induced in a host can be used by parasites to advance their own fitness.”
So, could this fungus actually take over humans like on “The Last of Us”?
“In a fantastical way, the logical links are there, but it’s not likely to happen in real life,” said Ian Will, a fungal geneticist at the University of Central Florida, according to National Geographic.
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