Behold the fungus that turns spiders into zombies and marches them to their deaths

As It Happens6:29Newly discovered fungus turns spiders into zombies

Tim Fogg walked past the zombie spider fungus many times over the years before he learned what it actually was.

As someone who explores caves for a living, Fogg would often see little globs of fuzzy white fungus on the walls of Ireland's subterranean networks, sometimes with spider legs sticking out of them.

Now, he's a co-author of a study that identifies those globs as a newly discovered species of fungus that takes control of spiders, essentially turning them into zombies, and marches them to their deaths.

Zombified spiders infected by deadly fungi in dark caves may be the stuff of nightmares for some people. But, for Fogg, it's a dream. 

"I find it fascinating and extraordinary and really intriguing," he told As It Happens host Nil Köksal.

Though, he admits, it's "sad for the spiders."

The findings are published in the journal Fungal Systematics and Evolution.

Discovered during a BBC shoot

It all started in 2021 in an abandoned gunpowder storage shed near Belfast. A film crew was shooting footage for the BBC nature program Winterwatch, when they stumbled across several dead spiders on the roof, enmeshed in a prickly looking white substance. 

They sent samples to Harry Evans of U.K. office of the Centre for Agriculture and Biosciences International, who theorized the crew had found a fungus not yet known to science. 

Fogg saw the documentary, and immediately recognized the stuff from caves around Northern Ireland and the Republic of Ireland. So he reached out to Evans, who promptly put him to work.

"Over the last two and a half years, we've been watching them and getting samples and culturing the samples and doing DNA sampling on them," Fogg said. "The results are a new species, and this interesting behaviour."

The fungus — called Gibellula attenboroughii after famed nature documentary host David Attenborough — appears to affect two cave-dwelling species of spiders, Metellina merianae and Meta menardi.

Both spiders prefer to spend their time in dark, dank places. But the fungus forces them to abandon the holes and crevices they call home, and march to open, high-up spaces, like cave walls or cellar roofs, to die. 

"When they're dead, they have a lot of long filaments coming out of them, with the spores on them," Fogg said.

The scientists theorize the spores are then carried on the breeze, raining down upon other, unwitting spiders.

If this sounds familiar, it's because Gibellula attenboroughii is one of many species of parasitic fungi around the world that take over and kill their hosts, which are usually insects. 

Andy MacKinnon, a forest ecologist in British Columbia who studies fungi, calls these "zombie fungi," and says they even exist in Canada.

"It's not an uncommon thing, but it's uncommonly interesting," MacKinnon, who was not involved in the study, told CBC.

Perhaps the best known example is Ophiocordyceps, a parasitic genus of fungi that infects ants and other insects. It grows inside a host, forces it to climb to a high point, then bursts through its body, usually the head, and showers spores upon its brethren below. 

It's the fungus that inspired The Last of Us, a popular video game and television series about a fungi-fuelled zombie apocalypse.

Gibellula attenboroughii is part of a totally different fungi family than its ant-exploding counterpart, says João Araújo, a mycologist at Denmark's Museum of Natural History, and another co-author of the study.

But the behaviour it induces — making its host defy its natural instincts by climbing up high to die — is very similar.

Some research suggests the zombie ant fungus works by flooding its host with the feel-good hormone dopamine in order to make it do its bidding. Other research suggests the fungus acts on the ant's muscles, rather than its mind.

"If you were the ant, your brain may be able to contemplate that your legs were moving all on their own and taking you to places you wouldn't normally go," MacKinnon said. "You might be able to ponder that as an ant."

Whether this new fungus bestows that particular horror on Ireland's cave spiders, or simply blisses them out with happy hormones, is not yet clear. 

"We don't know the mechanisms behind it," Araújo said. "This species was just discovered, there is a lot to investigate about it yet."

The pros of zombie fungi 

While zombie fungi are no friend to the ants of Brazil or the cave-dwelling spiders of Ireland, MacKinnon says they have an important role in the natural world, keeping their hosts species' populations in check. 

"They're a predator of sorts," he said. "They don't prowl around on four legs and chase the insects, but they are performing the same function in the ecosystem."

They pose no danger to humans, and may even be beneficial. 

Some kinds of zombie fungi have long been used in traditional medicine, for all kinds of things, including improving energy and libido. And some preliminary research suggests they could boost immune responses and help slow the growth of cancer cells.

That gives hope to Fogg, who spent years collecting dead spiders from dark caves.

"Hopefully, there's something in these amazing fungi that will help humans in the future medically," he said.