Zombie roaches and other parasite tales | Ed Yong

Elise Hu (0:00)

Where I live, October means pumpkins on porches and fake cobwebs stretched across just about every bush. My family has been planning their Halloween costumes for weeks. It's a holiday with ancient roots, and plenty of cultures around the world have their own traditions for honoring the dead and the mysterious. But whether or not you celebrate, it's a fun time to lean in to the strange and the spooky. For October's TED Talks Daily playlist, we have gathered five haunting talks covering everything from grieving crows to zombie roaches. They might give you a few chills, but they're also full of weird, wonderful discoveries that remind us just how fascinating our world is. Happy listening.

You're listening to TED Talks Daily, where we bring you new ideas to spark your curiosity every day. I'm your host, Elise Hue. Nature is full of creatures doing things that seem to make no sense at all. Would it surprise you to know that sometimes because something else is pulling the strings? Science writer Ed Yong has spent years writing about those somethings, parasites that hijack their hosts' minds and bodies. In this talk from 2014, he takes us into the macabre, often hilarious world of parasites, from a worm that drives crickets to leap into the water, to a wasp that leads a cockroach around like a dog on a leash. Then he asks an unsettling question. Could something similar be happening to us?

If you're able, I recommend watching this one on ted.com also because Ed shares some truly amazing and occasionally stomach-turning photos of these creatures in action. That's coming up right after a short break.

And now our TED Talk of the day.

Ed Yong (1:56)

A herd of wildebeest, a shoal of fish, a flock of birds. Many animals gather in large groups that are among the most wonderful spectacles in the natural world. And why do these groups form? The common answers include things like seeking safety in numbers, or hunting in packs, or gathering tomato breed. And all of these explanations, while often true, make a huge assumption about animal behaviour, that the animals are in control of their own actions, that they are in charge of their bodies. And that is often not the case.

This is artemia, a brine shrimp. You probably know it better as a sea monkey. It's small, and it typically lives alone, but it can gather in these large red swarms that span for meters. And these form because of a parasite. These shrimp are infected with a tapeworm. A tapeworm is effectively a long, living gut with genitals at one end and a hooked mouth at the other. As a freelance journalist, I sympathise.

The tapeworm drains nutrients from artemia's body, but it also does other things. It castrates them.

It changes their colour from transparent to bright red. It makes them live longer. And as biologist Nicholas Road has found, it makes them swim in groups. Why? Because the tapeworm, like many other parasites, has a complicated life cycle involving many different hosts. The shrimp are just one step on its journey. Its ultimate destination is this, the greater flamingo. Only in a flamingo can the tapeworm reproduce. So to get there, it manipulates its shrimp hosts into forming these conspicuous colored swarms that are easier for a flamingo to spot and to devour. And that is the secret of the artemia swarm. They aren't sociable through their own volition, but because they are being controlled. It's not safety in numbers. It's actually the exact opposite. The tapeworm hijacks their brains and their bodies, turning them into vehicles for getting itself into a flamingo. And here is another example of a parasitic manipulation. This is a suicidal cricket. This cricket swallowed the larva of a Gordian worm, or horsehair worm. The worm grew to adult size within it, but it needs to get into water in order to mate. And it does that by releasing proteins that addel the cricket's brain, causing it to behave erratically. When the cricket nears a body of water such as this swimming pool, it jumps in and drowns, and the worm wriggles out of its suicidal corpse.

Crickets are really roomy. Who knew?

The tapeworm and the Gordian worm are not alone. They are part of an entire cavalcade of mind-controlling parasites, of fungi and viruses, and worms and insects and more that all specialize in subverting and overriding the wills of their hosts. Now, I first learned about this way of life through David Attenborough's Trials of Life about 20 years ago, and then later through a wonderful book called Parasite Wrecks by my friend Carl Zimmer. And I've been writing about these creatures ever since. View topics in biology and throw me more. It's like the parasites have subverted my own brain. Because after all, they are always compelling, and they are delightfully macabre. When you write about parasites, your lexicon swells with phrases like devoured alive and burst out of its body.