The moment I saw it, I thought, my God,
I’m looking at Cordyceps.
I’m Lizzie Daly, a biologist and wildlife broadcaster.
A number of years ago,
I had the opportunity to venture into a beautiful part of the world.
It’s a place called Danum Valley, and it sits in Borneo.
I remember arriving, feeling really excited.
This is a place with, you know, clouded leopards, Orangutans.
You’ve got, you know, Rhinoceros Hornbills flying over.
You can hear them flapping.
You can feel the warmth and the humidity of an environment like this rainforest.
And we were really lucky
because we were there at a time where there was a unique event happening.
It’s called ‘mass flowering’.
It’s basically where, you know, all these trees,
life, and fruit burst into flower and into life.
And it creates this kind of supercharged environment.
At the beginning of our trip, we started heading on these kind of overgrown trails.
And, you know,
the minute you step on these trails, you are immersed in this environment.
You can feel the humidity.
It’s raining on and off all day, so you’re damp.
There’s lots of noise,
you’re surrounded by the sounds of these Emperor cicadas, which is kind of
almost like the pulsing heartbeat of the rainforest.
You know, I like to think I’m quite comfortable in natural environments
and hostile environments,
but there is nothing like walking through a dense rainforest by yourself.
You are truly swallowed up by the environment.
Suddenly you’re in an overwhelming chorus of just the rainforest,
You’re being, you know, rained on every 5 minutes.
I would keep stopping
along this path to notice some of the life around me,
and I remember stopping,
and I remember stopping,
and I saw a trail of ants.
You know, ants are a big player in this environment.
And these ants were going across the footpath
that I’d just crossed, and I was watching them for a while.
I noticed that next to the trail
there were a few individual ants acting kind of strange.
There was one ant that was carrying off another dead ant.
I thought, you know, not much of it perhaps that ant was ill.
But there was another ant kind of moving slowly.
It wasn’t part of the rest of the trail, constantly cleaning itself.
It would stop and, you know, clean its antenna and its legs quite thoroughly.
And it was just moving in a really odd way.
Later on in the day, as I was walking along a different trail,
I was standing next to this trunk and it was kind of covered in mosses,
this beautiful, kind of vibrant green that you can only get in this kind of environment.
And I noticed a kind of like a mossy lump
that was attached to this tree, and I realised it was a cicada.
But the cicada wasn’t singing, it wasn’t calling, and it wasn’t moving at all.
I realised that that cicada was actually dead.
It was covered in this kind of fungus appearance,
and it basically looked like it had melted into the side of the tree.
I wasn’t looking at a natural death here.
All of a sudden, this beautiful environment
which has so much wonder and beauty in it, suddenly the darker side came to the fore
and at that moment changed my entire perception of this environment.
I was looking at Cordyceps.
When we think of a fungus, images of mushrooms,
crazy toadstools, or just blue mold on some bread comes to mind.
It all seems quite benign, but Cordyceps is anything but benign.
It’s a parasitic fungus,
that infects and can even manipulate the behavior of its animal host.
That sounds sinister, but here’s what probably happened to the ant that I saw.
When a Cordyceps spore landed on the ant’s body,
It would have released a mix of proteins
and enzymes such as Chitinase to break down the ant’s harder outer-shell,
and the infective hypha used mechanical pressure
to basically drill through the exoskeleton.
Once inside the ant, Cordyceps hyphae set about reproducing.
But unlike, say, a bacterial infection, these cells now start to get organised,
joining together to create a mycelial network.
Similar really to the networks that run underground through a forest.
But in this case, through the body of the ant
using the ant’s own cells as fuel.
A few years ago, in fact, a research team in the US painstakingly scanned
an infected carpenter ant, discovering that the mycelial network
actually wrapped its way through the individual muscle fibers of the ant.
What’s more, this network seemed to leave the brain intact.
The traditional view was that the fungus controlled the ants behavior
through a cocktail of mind bending drugs.
But this new research has led people to liken Cordyceps to a macabre puppet master,
cutting off the brain from the body
and controlling the limbs of the ant through its network of mycelial filaments.
Then Cordyceps is ready for its grim finale.
In the case of the zombie ant fungus
it drives the infected ant’s body to climb to the top of a nearby plant.
Once the fungus detects is at the perfect height,
the ant is then forced to lock its tiny jaws around a bit of foliage.
And here, finally, the ants dies in what has become known as
death grip.
The Cordyceps mycelium causes the ant to bite so hard
that it destroys the muscle filaments that slide past each other,
causing the jaw to lock shut forever.
Finally, a fruiting body sprouts out the back of the ant’s head,
showering down fungal spores on the rainforest below,
hoping to land on another poor, unsuspecting ant
restarting the whole cycle again
There are over 500 species of Cordyceps that have been identified,
and we can safely say there are many more that we don’t even know about.
Each species of Cordyceps has evolved to infect a specific host,
such as an ant, a cicada, a caterpillar, or even a spider species.
We understand the precise nature of very few of these relationships.
Little is known of the true biodiversity of the fungi kingdom.
Around 120,000 species have been formally described,
but it’s thought there may be, as many as 2.2 to 3.8 million species.
We are only beginning to scratch the surface of what evolution has to offer.
But this insidious fungus crafts nature’s very own walking dead,
earning its victims the very worst of deaths.
I think it’s that aspect of its lifecycle that really fires up our imagination.
Earning names like ‘zombie ant fungus’
and inspiring science fiction
such as ‘The Girl With All The Gifts’
and video games such as ‘The Last of Us’,
where parasitic fungus has jumped
from infecting ants and cicadas to infecting and controlling humans.
But before you have nightmares, you’ll be glad to know that
it doesn’t infect humans…
yet.
