WEBVTT - How Does the 'Zombie Ant' Fungus Work?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff,

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<v Speaker 1>Lauren vogelbam here. Zombies are a horror trope for a reason.

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<v Speaker 1>For many reasons, really, but one is that we humans

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<v Speaker 1>tend to like the idea of being in control of

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<v Speaker 1>our own bodies and behavior, and in stories, the walking

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<v Speaker 1>dead are reduced to mindless doers of damage and often modernly,

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<v Speaker 1>spreaders of whatever infectious disease has caused the dead to rise.

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<v Speaker 1>There are many real life infections and conditions that can

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<v Speaker 1>alter a person's behavior, all horrific in their own right,

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<v Speaker 1>but none we know of could cause a full on

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<v Speaker 1>George Romero's style apocalypse or the Last of Us style apocalypse.

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<v Speaker 1>In the video games and television series The Last of Us,

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<v Speaker 1>a brain hijacking fungus evolves from the infecting insects and

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<v Speaker 1>other arthropods to infecting human beings. And don't worry, that's

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<v Speaker 1>the only spoiler we're going to give here. But today,

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<v Speaker 1>let's talk about the real life fungi that inspired the series.

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<v Speaker 1>Cordyceps and Afia. Cordyceps are each a genus of fungi

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<v Speaker 1>that are often parasitic to arthropods like ants, spiders, and wasps.

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<v Speaker 1>Fungi in general grow from spores, then consume living or

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<v Speaker 1>dead material like wood in order to grow root like

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<v Speaker 1>structures called mycelium and fruiting bodies like mushrooms that produce

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<v Speaker 1>more spores. But instead of in wood, Cortceps and Affia

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<v Speaker 1>cordyceps tend to grow in arthropods that in itself is

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<v Speaker 1>nothing very special. A fossil evidence of fungi growing in

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<v Speaker 1>insects has been found as far back as one hundred

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<v Speaker 1>and five million years ago, and over a thousand fungi

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<v Speaker 1>with insect hosts are known to exist today. But these

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<v Speaker 1>two genera of fungi can actually change an animal's behavior

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<v Speaker 1>when they're ready to spore in order to spread those

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<v Speaker 1>spores as far as possible. Take, for example, a species

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<v Speaker 1>of Apia cordyceps. The parasitizes carpent durants and hijacks the

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<v Speaker 1>ants behavior during the last days of its life. This

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<v Speaker 1>phenomenon caught the eye of British naturalist Alfred Russell Wallace

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<v Speaker 1>when he was in Indonesia back in eighteen fifty nine.

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<v Speaker 1>Even a newcomer to the area could see that something

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<v Speaker 1>was seriously wrong with some of the ants in the rainforest.

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<v Speaker 1>After all, carbondurants are generally pretty predictable in their behavior.

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<v Speaker 1>They work as a team, and each ant has a

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<v Speaker 1>very specific job, like building the nest, gathering food, or

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<v Speaker 1>caring for the queen. When an ant is infected with

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<v Speaker 1>the fungus, the fungus grows unnoticed in the ant's body

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<v Speaker 1>for a while, feeding on the ant until the fungal

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<v Speaker 1>cells account for over half of the ant's body mass.

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<v Speaker 1>All this time, the ant has been doing its usual

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<v Speaker 1>job and living its life. One day it begins to

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<v Speaker 1>act very differently. Breaking off from the colony. It stumbles

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<v Speaker 1>around by itself all day and night, climbing higher and

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<v Speaker 1>higher into the trees. Eventually, the ant clasps a leaf

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<v Speaker 1>for stem with its strong mandibles and dies. Check in

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<v Speaker 1>a week later, and you'll find the dead ant's body

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<v Speaker 1>covered in a brown mat of hair like structures, with

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<v Speaker 1>a beige stalk having erupted from a place near its head.

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<v Speaker 1>This stalk releases millions of tiny spores that float away

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<v Speaker 1>on the air for more ants to step on, thus

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<v Speaker 1>beginning the whole cycle over again. That chomping onto a

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<v Speaker 1>leaf for stem behavior by the way is how we

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<v Speaker 1>know that this kind of behavior altering fungal parasitism is

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<v Speaker 1>pretty ancient. Leaf scars created by an ant death grip

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<v Speaker 1>have been found on fossils at least forty eight million

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<v Speaker 1>years old. In all that time, carbenter ants have evolved

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<v Speaker 1>some strategies for avoiding these fungi, at least they try

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<v Speaker 1>their best. Many ant species groom each other in an

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<v Speaker 1>attempt to remove spores from their friends, while others fray

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<v Speaker 1>their nests with fungicidal poisons and seal off parts of

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<v Speaker 1>their nests. When infections arise, a whole ant colony will

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<v Speaker 1>relocate if necessary. But how does the fungus affect the

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<v Speaker 1>ants behavior to the extent that it does. It's a

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<v Speaker 1>question that's baffled generations of scientists over the years. Some

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<v Speaker 1>have argued that the ants aren't hijacked at all, that

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<v Speaker 1>certain protocols have evolved in response to a fungal infection,

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<v Speaker 1>and that the individual ants wander off not because they're

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<v Speaker 1>being influenced by the fungus, but to avoid infecting the

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<v Speaker 1>rest of their colony. And despite the tropes about zombies

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<v Speaker 1>and brains, a twenty seventeen study published in the Proceedings

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<v Speaker 1>of the National Academy of Sciences found that it's possible

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<v Speaker 1>that the ant's brain isn't involved in the whole process

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<v Speaker 1>at all. The researchers found that as the fungus grows

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<v Speaker 1>inside the ant's body, its cells create an interconnected network

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<v Speaker 1>of fibers that surround the ants muscle fibers, and that

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<v Speaker 1>it's this network that is most likely coordinating the ants movements.

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<v Speaker 1>They did find the fungus in the insect's head, but

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<v Speaker 1>not in its actual brain. In a press release, the

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<v Speaker 1>lead author of the study, an entomologist by the name

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<v Speaker 1>of David Hughes, said, we found that a high percentage

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<v Speaker 1>of the cells in a host were fungal cells. In essence,

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<v Speaker 1>these manipulated animals were a fungus in ants clothing. Pretty

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<v Speaker 1>much everything except the brain had been taken over entirely

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<v Speaker 1>by fungal cells, which led the researchers to believe that

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<v Speaker 1>the fungus might be preserving the brain for a reason,

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<v Speaker 1>maybe in order to help the ants survive until it

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<v Speaker 1>can perform its final death bite. To be fair, ant's

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<v Speaker 1>brains are pretty small, and they make up for that

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<v Speaker 1>by having clusters of neurons throughout their bodies that help

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<v Speaker 1>control different work, like the movement of a pair of

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<v Speaker 1>legs or receiving signals from an antenna. So although these

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<v Speaker 1>findings are compelling, it's still not crystal clear what's going

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<v Speaker 1>on between these parasitic fungi and their victims. But at

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<v Speaker 1>least it is clear that it would be extremely difficult

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<v Speaker 1>for a fungus to start hijacking human bodies in the

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<v Speaker 1>way that cordyceps and a few cordyceps do with arthropods,

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<v Speaker 1>so that's one less thing to worry about. Today's episode

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<v Speaker 1>is based on the article Meet the Zombie ant Fungus

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<v Speaker 1>that inspired HBO's The Last of Us on how Stuffworks

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<v Speaker 1>dot com, written by Jeslin Shields. Brain Stuff is production

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<v Speaker 1>of iHeartRadio in partnership with how Stuffworks dot Com and

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<v Speaker 1>is produced by Tyler Klang. Four more podcasts my Heart Radio,

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<v Speaker 1>visit the iHeartRadio app, Apple Podcasts, or wherever you listen

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