Placeholder Image

Subtitles section Play video

  • [Music]

  • ED YONG: 1977.

  • A big year.

  • Saturday Night Fever.

  • Star Wars.

  • Apple becomes a company.

  • The first boomboxes take to the street.

  • Voyager 1 launches on an expedition

  • into the outer solar system.

  • And a small submersible named Alvin

  • begins a dive to the bottom of the Pacific Ocean.

  • [Splash]

  • [motor whirring]

  • February 1977.

  • 250 miles north of the Galapagos islands.

  • A place where two continental plates

  • are pulling away from each other on the ocean floor.

  • Three men in a miniature sub set off

  • on an expedition that would completely

  • change our view of how extreme life on earth can be.

  • They were on the hunt for deep-sea hydrothermal vents

  • caused by the rift between those continental plates.

  • Their existence had been predicted for decades,

  • but no one had ever seen them.

  • At a depth of 7,500 feet their temperature sensors spiked

  • - they had reached volcanically super heated water gushing

  • through the ocean floor.

  • But they also found something that utterly surprised them:

  • life.

  • In extreme abundance.

  • Weird and wonderful.

  • How could this underworld support so much life?

  • There is zero sunlight here.

  • Skull crushing pressures and yet the Alvin crew

  • have discovered a hidden ecosystem.

  • This was NOT what they had expected.

  • They were the first to ever set human eyes

  • on this environment - rich and full of life,

  • like an underwater rain forest.

  • And then they found...

  • ...the worms.

  • These bizarre creatures are tubeworms.

  • They are giants that can grow over six feet long.

  • Their bodies are encased in white tubes anchored

  • to the rocks.

  • At their upper end is a spectacular crimson plume.

  • It looks like a tube of lipstick that's been pushed out too far.

  • Or like maybe Mick Jagger's lips?

  • The Alvin team knew that they had

  • come upon a wonderful zoological oddity.

  • What they didn't know was that the worms would reveal

  • an undiscovered eco system, that we didn't even think

  • was possible.

  • The Alvin crew collects one of the worms

  • and gives it to this man.

  • This is Meredith Jones, the Smithsonian Institution's

  • curator of worms, and as befits his role as chief worm guy

  • he gives the thing a name: Riftia pachyptila.

  • Jones dissects the worm.

  • And he encounters something - that to us,

  • as non-worm people - is really weird: Riftia has no mouth,

  • no gut, no anus.

  • This thing has no way in, no way out.

  • How does it survive if it can't eat, digest, poop?

  • Well Jones, as a curator of worms,

  • had seen this kind of thing before - gutless worms.

  • Instead of a gut these worms have an organ

  • called a trophosome.

  • It's brown and spongy and makes up half the creature's length.

  • A trophosome isn't technically a gut,

  • but it does deal with nutrition.

  • But this trophosome was different

  • because there was nothing remotely like food in it.

  • Instead, it was packed with crystals of pure sulfur.

  • Something was going on inside this worm

  • that Jones had never seen before.

  • And that's when Colleen Cavanaugh enters the picture.

  • [Discotech music]

  • COLLEEN CAVANAUGH: I was a first year graduate student

  • at Harvard taking a course called Nature and Regulation

  • of Marine Ecosystems.

  • And the professors organized so that there

  • were four talks on the vents.

  • ED: Jones came in to give a talk about his worms.

  • It was a long talk.

  • Amazingly I was still awake when he

  • mentioned that in this trophosome tissue

  • it had sulfur crystals in it.

  • ED: What Jones knew that the water spewing

  • from the hydrothermal vents had a high concentration

  • of hydrogen sulfide, a potent toxin to most lifeforms.

  • So maybe the trophosome wasn't an organ to help feed the worm

  • - maybe it was a filter - something

  • to help get rid of all the poisonous hydrogen sulfide.

  • And when she heard that...

  • I immediately jumped up and said, "It- it's clear!

  • They must have symbiotic sulfur-oxidizing bacteria

  • inside of their tissues that are feeding the worm."

  • ED: Bacteria?

  • Bacteria!

  • CHORUS OF BACTERIA (SINGING): BACTERIAAA!!!

  • ED: And how did Jones react?

  • He was a little bit dismissive.

  • It was a little bit like, you know, sit down kid.

  • Ultimately I was able to get some tissue.

  • ED: Of the trophosome?

  • Of the trophosome.

  • So it looks like little pieces of brown tissue.

  • COLLEEN: It took a lot of detective work, chemical

  • analyses, DNA stains, scanning electron microscopy,

  • transmission electron microscopy.

  • ED: Ultimately?

  • I was right.

  • CHORUS OF BACTERIA (SINGING): BACTERIA!!!

  • ED: So Colleen discovered that trillions of bacteria are

  • living in the trophosome, using the hydrogen sulfide from

  • the vents as an energy source...

  • ...in a process called chemosynthesis.

  • COLLEEN: Chemosynthesis is a process

  • using chemicals such as hydrogen sulfide as energy sources.

  • ED: As opposed to photosynthesis which uses sunlight.

  • Plants do photosynthesis.

  • They need wat-eh-hem, um.

  • They need water and carbon dioxide,

  • which they transform into sugars using the energy in...

  • sunlight.

  • But the worms can't do that.

  • COLLEEN: It's dark.

  • We're two and a half kilometers down up to,

  • I mean to even deeper.

  • That's, you know, over a mile and a half deep.

  • So it's complete darkness in the deep sea.

  • ED: So instead of sunlight the bacteria ingest and process

  • the sulfides from the vents.

  • [sucking/slurping sound] In doing so they excrete sulfur,

  • but they also release energy which

  • they use to make food for themselves and for the worms.

  • [Bacteria eating, burping, and farting.]

  • And that's what chemosynthesis is.

  • Making food not with solar power, but with chemical power.

  • So it's apparent from a mouthless and gutless

  • point of view that the worm is benefiting from getting

  • it's food from the bacteria.

  • When you're a bacterium inside of the animal

  • and you've somehow convinced the host

  • to provide you with the sulfide and the oxygen

  • then you're, you have easy street.

  • ED: So it's good for everyone?

  • That's right

  • Ok so one things not quite tracking with me here.

  • So, if Riftia has no mouth how do

  • the bacteria get into it in the first place?

  • So we found out that the bacteria were actually

  • getting in through the skin, through the body

  • wall into the, the worm.

  • Wow!

  • Ok so how do the sulfides get in?

  • So the hydrogen sulfide goes in via the plume.

  • (Pause) So they do have a mouth?

  • It's more, it's more like a lung.

  • But a lung is for breathing...

  • Thats right.

  • It's breathing oxygen just like you and I.

  • But it's also effectively breathing

  • hydrogen sulfide because that's what

  • the bacteria need to produce organic compounds

  • via chemosynthesis.

  • And that deep red of the plume I mean

  • it almost looks like blood.

  • COLLEEN: It is blood.

  • They have a blood supply all the way through it.

  • And the blood is carrying the hydrogen sulfide,

  • the oxygen into the trophosome to the bacteria.

  • ED: Huh.

  • And this type of chemosynthesis is it just a worm thing?