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How Giant Tube Worms Survive at Hydrothermal Vents | I Contain Multitudes


[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? Not at all. It’s ubiquitous, or it’s,
it’s widespread in nature. Wherever sulfide and oxygen
exist we can look for it and it’s found in
many of those places. ED: Chemosynthesis had been
discovered a hundred years ago, but after Colleen’s
discovery, it was established as the basis
of this entire new ecosystem, 7,500 feet below the surface. And in fact,
chemosynthesis might have been the way the earliest
lifeforms on the planet found a way to survive. COLLEEN: It took kind of getting
away from sunlit environments to see that it’s really possible
and that the whole ecosystem is dependent on the chemicals
– in this hot water that’s coming up. It’s like the fountain of life. ED: Very cool, these
vent creatures. COLLEEN: It’s
actually very warm. Well they’re in hot vents. [Laughs] Sorry. And I think we’ll
leave it at that. If you’re especially
curious about the story behind this episode,
check out the link below for an article
that dives even deeper into these amazing microbes. And don’t forget to
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for more weekly videos. Thanks for watching.

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