All language subtitles for David.Attenboroughs.Light.On.Earth.2016.1080p.WEB.H264-GRASHOPR_track3_[eng]

(gentle music)

(owl hooting)

- As dusk gives way to twilight,

the encroaching darkness is lit by life.

These dancing lights around me

are produced by fireflies,

creatures that have the strange
ability to produce light.

They bioluminesce.

(dramatic music)

And fireflies are not alone.

Scientists are finding evermore strange

and wonderful glowing life
forms all around the world.

(dramatic music)

Living light has always fascinated me,

and the discovery of more
and more luminous creatures

raises more and more questions.

Why?

What is the light for?

And how is it made?

In recent years, scientists have begun

to find answers to those questions,

and in doing so, they've taken us

into a world that is
utterly unlike our own.

(dramatic music)

However astonishing these
images look, they are all real.

(dramatic music)

With help from new cameras, one
designed just for this film,

we can reveal this
extraordinary phenomenon

as it has never been seen before.

(dramatic music)

(bugs chirping)

(owl hooting)

Bioluminescence holds many mysteries,

but we do know that fireflies use it

to attract the opposite sex.

(gentle upbeat music)

Each species has its own flash code,

and we can join in the conversation.

(gentle upbeat music)

I'm going to use this rod
to fish for fireflies.

It's the actual rod used by the scientist

who was the first to decipher

the various call signs of fireflies.

And there are 15 different species,

at least around here,
each with its own signal.

Biologists Jim Lloyd used the
rod to imitate male fireflies

and so decode their
various light patterns.

He discovered that the call sign consisted

partly in the actual flight
path of the species concerned.

There are, for example, some
fireflies which move steadily,

horizontally, like that.

And there are others
which turn their light on

as they climb, like that.

But in addition to the flight path,

they flash a particular signal.

It's rather like Morse code.

So I should be able to
use this light myself.

There's a female amongst
these leaves here,

which will emit a single flash,

and the male of her species

waits for precisely four seconds

and then answers back with a flash,

whereupon she immediately
gives another flash, like that,

and the male then knows that

he's going to be a welcome visitor.

But the message has recently been shown

to be more than a simple signal for sex.

A female judges the
quality of a male's genes

by the precision of his timing

and the brightness of his light.

(gentle upbeat music)

She encourages her chosen suitor

by directing her lanterns towards him.

(gentle upbeat music)

And it seems this male sent
out all the right signals.

We are now discovering

that this language of light
even has local dialects.

(gentle upbeat music)

Throughout the summer months

from Florida to Southern Canada,

gardens, fields and forests

sparkle with these mating messages.

Time-lapse photography reveals

the extraordinary extent
of this courtship.

(dramatic music)

Some species flash only at dusk.

Others prefer the forest
canopy for their light show.

Some species make their
flashes more conspicuous

by choosing the very darkest
places in which to display.

I can see virtually nothing
here except the flashes.

And this particular species
has another trick too.

It synchronizes the displays.

Individuals flash together.

(gentle upbeat music)

Each individual is
triggered by its neighbor,

and soon waves of light
pulsed through the woods.

(gentle upbeat music)

Speeded up, the wave becomes clearer.

(gentle upbeat music)

Between the waves, an
impressed female can respond

with two flashes of her own,

and the males hone in on her.

But she can only choose one.

(gentle upbeat music)

These displays peak for
just a few nights in June,

which could explain why they
were only recently discovered.

Why they all flash together
is still a mystery.

(gentle upbeat music)

(birds singing)

It's surprising how little we
know about bioluminescence.

Fireflies are perhaps the best understood,

but some living light is
still very perplexing indeed.

With dawn, the sexual
signals of the fireflies

are drowned by the
increasing flood of light.

The flies take refuge in the undergrowth,

away from the sharp-eyed
predators of the day.

But right now, light is being produced

by life in the soil under my feet.

(gentle music)

The threads of certain fungi

form a glowing underground network.

(gentle music)

But why would a fungus shine

in the permanent darkness of the soil?

We simply don't know.

And for years, fungus bioluminescence,

like much other living light,

was written off as a beautiful byproduct

of evolution with no function.

But some species only glow above ground

and only at night when
their intense green light

is very obvious.

(gentle music)

If it was just a biochemical accident,

then surely they would shine all the time.

The glow certainly attracts insects

and the theory is that these visitors

spread the fungal spores.

(gentle music)

So here too, just as with fireflies,

we're learning new things all the time.

(tense music)

But much living light
remains a beautiful enigma.

And throughout history,
stories of bioluminescence

were often thought to be pure fiction.

In the 1870s, Jules Verne,

the French science fiction
novelist wrote this in his book

"Twenty Thousand Leagues Under the Sea."

"At seven o'clock in the evening,

our ship, half immersed, was
sailing in a sea of milk.

At first sight, the
ocean seemed lactified.

The whole sky seemed black by contrast

with the whiteness of the waters."

Jules Verne may have based his story

on a myth told to him by sailors.

But in 1995, the captain
of a British vessel

wrote a real life account
in his ship's log.

"At 1800 hours on a clear, moonless night,

while 150 miles east
of the Somalian coast,

a whitish glow was
observed on the horizon,

and after 15 minutes of steaming,

the ship was completely
surrounded by a sea

of milky white color with a
fairly uniform luminescence.

And it appeared as though the ship

was sailing over a field of snow

or gliding over the clouds."

(gentle music)

Reports like this are rarer
than the supposed sightings

of the Loch Ness Monster,

and there was no photographic evidence.

Some scientists, including
marine biologist Stephen Haddock,

were curious and sought
confirmation from above.

- [Stephen] We wondered if you could find

one of these ship reports

where they record sailing
through one of these milky seas,

and actually find the
corresponding satellite data

that cover that area at that same time.

So we looked at this satellite
from the ship report in 1995

and it was somewhat of a eureka moment.

We cleaned up the noisy
sensor image from the camera.

We mapped it onto the ship track,

and this 300 kilometer
feature emerged on the map

matching exactly with what
the ship had reported.

So it was really an amazing moment.

We are able to document the full extent

of the milky sea over
three successive nights

as it rotated with the currents.

- So satellite images from the space age

validated a piece of maritime folklore.

On rare occasions, the oceans do glow.

But what was causing a glow so bright

that it could be seen from space?

The answer can be found at the
back of a neglected fridge.

(gentle music)

Left for a couple of days,

this sea bream starts to glow.

(gentle music)

The fish itself has no
light producing ability.

The glow is in fact produced by bacteria

that are found in almost all sea water

when they start to feed on decaying fish.

On rare occasions when currents

and temperatures cause a large
bloom of algae in the ocean,

these very same bacteria
also feed on dying algae.

Once they reach a critical concentration,

their secretions trigger others to glow.

They were glowing in such numbers

that they can be detected
by a satellite in orbit.

(gentle music)

Bacteria are among the
most ancient forms of life,

so they may have been the very
first living things to glow.

But why they did so is still debated.

Today, some animals have stolen
the genes of the bacteria

and incorporated them into their own DNA.

Others have simply kidnapped
the bacteria themselves.

(gentle upbeat music)

These lights are made by captives

which are farmed in special organs

below the eyes of flashlight fish.

(gentle upbeat music)

They have harnessed the
bacterial glow for many purposes.

We can only see them

because our special
cameras use infrared light.

But to a predator, the
fish look like this,

a confusion of lights, which makes it hard

to pick a single target.

(gentle upbeat music)

Just before they change direction,

the fish give a quick blink.

(gentle upbeat music)

These lights have other functions too.

They act as headlights to
illuminate the sea floor

as the fish search for food.

(gentle upbeat music)

They may even help a fish to
flirt with the opposite sex.

(gentle upbeat music)

Unlike their captive bacteria,

flashlight fish use living light

for functions we now understand.

But how is the light made?

While it might appear magic,

it's actually a straightforward
chemical reaction

that happens when a substance is mixed

with a particular enzyme, like this.

(gentle upbeat music)

Hey presto, light.

The exact chemical formula
varies according to the species.

The reaction is very similar to that

with which bacteria produce energy.

Indeed, it could well be
that the first luminescence

was a byproduct of that process.

An evolutionary accident
that has been co-opted

by the fish to help them survive.

The chemicals involved are quite harmless.

In fact, you can actually buy a lollipop,

which when you put it in hot water glows.

But to be truthful, I don't really find

that very appetizing.

Perhaps at the back of my mind,

there's a memory of those
bacteria on rotting fish,

which tells me that things that glow

aren't all that nice to eat.

Bacteria may have been
the first living lights,

but then many other organisms
also developed the ability.

From jellyfish to fungi and insects,

bioluminescence has evolved
independently over 50 times,

and is now produced by
thousands of different species.

And defense seems to be a common function.

(birds singing)

Millipedes are found across the globe.

Many are active during the day,

scuttling across the damp forest floor.

They can do this with impunity

because they're deadly poisonous.

Their bright colors are a
clear message to predators.

"Do not eat me.

I'm laced with cyanide."

(gentle music)

But what about millipedes
that are active at night?

They're no less toxic

than those that are active during the day.

But of course, colors at
night are no warning at all.

Could it be that luminescence is a way

of warning off nighttime predators?

These extraordinary
millipedes are only found

in the high mountains of California.

Their bioluminescence has
never been filmed before.

They can't be sending signals

to one another because they're blind.

Their living light evolved separately

from bacteria from a chemical process

that helps millipedes conserve
water in dry environments.

But since the millipedes
already contained cyanide,

the light evolved a function.

To my eyes, he doesn't look very bright,

but my eyes are not the
eyes of a nighttime predator

or indeed of our specialist camera,

and to both of them, this
could look very bright indeed

and be a real warning.

When scientists made clay
models of these millipedes,

half of which glowed, nocturnal predators

were more likely to attack
those that didn't glow.

(tense music)

This simple experiment
produced a clear result,

living light can act as a warning.

(gentle music)

But proving the function

of bioluminescence is not always so easy,

as a recent discovery has shown.

(gentle music)

These surely are like
creatures from science fiction,

luminous earthworms.

A few years ago,

a lady living in the Loire
Valley in Central France

went out during the
evening to look for a dog

which was digging a hole in the garden,

and in the bottom of the
hole, the soil was glowing.

It was these earthworms.

She could hardly believe her eyes.

And she went and told
people what she had seen,

and few people would believe her.

The species of worm was already known.

It lived over quite a lot of France,

but no one had ever seen it glow before,

perhaps such because few
people went out in the middle

of the night digging a hole,
especially without a light.

But eventually science
recognized these creatures.

But why should they bioluminesce

in the darkness of the soil?

Nobody knew.

(gentle upbeat music)

This blue light had gone
unnoticed by science until 2010

when biologists Marcel Koken
first saw their eerie glow.

- We are trying to find out why

this animal produces light,

a thing living underground,
why producing light?

No use for it apparently.

- [David] Is it just a byproduct
of some internal chemistry

or could the glow be used
to frighten off attackers?

These ground beetles
are voracious predators

and they love earthworms.

The worms look like ordinary
ones until the light goes out.

Our special camera gives
us a privileged view

of what's happening in the dark.

(gentle music)

Marcel's experiments have shown

that the worms can
control their brightness.

When the beetle touches part of the worm,

it's light gets brighter.

- So it could be that in case
a predator tries to bite it,

it lights up, that scares the predators.

Predator goes off and
the earthworm can escape.

- The beetle bites

and the worm's entire
body bursts into light

as it struggles to break free.

But the beetle doesn't
seem put off by the glow.

(gentle music)

If this is defense, it isn't working here.

Marcel is still looking for the function.

Perhaps other predators are put off,

or perhaps the worms use
light to find each other.

So it seems that this beautiful glow

has a function which we
still don't understand.

The world of living light
is full of mysteries.

The French worms went
unnoticed for so long

because they produced their
eerie light underground.

But there are rare
occasions when luminous life

is all about revealing yourself.

(gentle upbeat music)

(gentle music)

May, 2015.

While the sudden aurora
illuminates the night sky above,

the sea below produces
a strange blue glow.

(waves crashing)

(gentle upbeat music)

Each wave causes a
ripple of intense color.

(waves splashing)
(gentle upbeat music)

The animals in the bay notice it first.

Wading birds are attracted

to small crustaceans caught in the glow.

(gentle upbeat music)

Each movement alerts others
to this rare spectacle.

People gather to marvel at
this once in a lifetime event.

- Look at this.

- Oh, wow.

- [Spectator] Ah, that is amazing.

I've never seen anything
like this before in my life.

(spectator laughs)
(water splashes)

- [Camera Operator] That's wicked.

(gentle upbeat music)

(spectator laughs)

- [Spectator] There he is.

(water splashes)
(gentle upbeat music)

(spectator laughs)

- It may look like something

from Willy Wonka's chocolate factory,

but the phenomenon is real.

A mass bloom of microscopic organisms

caused by a rare combination
of climate and nutrients.

Under this microscope, I've got
a drop of ordinary seawater,

and it's full of tiny organisms

invisible to the naked eye
called dinoflagellates.

And if I disturb them in some way,

they combine two chemicals in their body

to produce a flash of light.

Watch.

(gentle upbeat music)

Dinoflagellates are one

of the biggest single
celled organisms known.

They're 1000 times bigger than bacteria.

They're neither animal nor plant,

but have characteristics of them both.

And when conditions are right in the sea,

as they were in Tasmania, they
bloom in enormous numbers.

Bioluminescent tides, like
this one, are certainly rare.

However, dinoflagellates
are found in huge numbers

all over the world.

They're among the most widespread

of all bioluminescent life.

Wherever they exist, these
single celled creatures

highlight anything that moves.

But why do dinoflagellates
behave in this way?

It's certainly not to entertain us,

though it obviously does.

Well, it could be that it's
a kind of burglar alarm,

that when a shrimp or some other animal

that feeds on the dinoflagellates

by filtering them out comes
along and starts to feed,

it is in doing so illuminating itself.

So that attracts the attention
of perhaps bigger fish

that might feed on the shrimp.

Just as a flashing burglar alarm

alerts the police to a thief,

the dinoflagellates expose
their attacker to its enemies.

(tense music)

The shrimp is revealed to
cuttlefish, with fatal results.

And so the cuttlefish can
hunt in total darkness.

But while the dinoflagellates'
light could work in this way,

it's still debated if
that's why they do it.

(gentle music)

Whatever the reason, the
magic created by their light

can be one of nature's
most magical spectacles.

(dramatic music)

(water splashing)

Bow riding dolphins are
revealed as dazzling outlines.

(water splashing)
(dramatic music)

Whenever these lights appear,

the way life in the ocean
hunts and hides is transformed.

Perhaps dolphins are guided to their prey

by the light of the dinoflagellates.

(dramatic music)

Only now has it become possible

to film these scenes with such clarity,

but every night spectacular light shows

like this play out somewhere
in the vastness of the oceans.

(dramatic music)

(waves crashing)

While exactly how dinoflagellates

use bioluminescence remains unproven,

there are other instances

when the burglar alarm effect

has been clearly demonstrated.

(tense music)

Caribbean coral reefs

are some of the most well dived
waters in the world, by day.

(birds squawking)

(water splashing)
(tense music)

At night, it's a different world.

A crab searches for a tasty morsel.

This is just what it's looking for,

the delicate tentacles of a brittle star,

a relative of starfish.

(tense music)

But the brittle star has a
surprisingly effective defense.

(light zapping)

When disturbed, it
unleashes a dazzling weapon,

raising the alarm.

(light zapping)
(tense music)

Having been revealed, the
crab makes a run for it.

(tense music)

And the normally well
camouflage crustacean

becomes easy prey for the
octopus, even in the gloom.

Scientists have only recently proved

the light helps the brittle
star drive off predators,

or better still, to get them eaten.

(tense music)

It's in the open water where
there's nowhere to hide

that the burglar alarm
defense is most effective.

Fish hunt small invertebrates

silhouetted against the night sky.

Ostracods, tiny crustaceans,

no bigger than a grain of
sand emerge from the reef.

Cardinal fish are common
predators of the small and unwary,

but when they strike an ostracod,

they get more than they bargained for.

The ostracod discharges a
bioluminescent flash bomb,

one of the brightest
forms of living light,

and the cardinal fish
quickly spits it out.

(gentle music)

The light is so bright that it shines

through the body of the fish,
temporarily blinding it,

and this normally invisible fish

becomes an easy target for a predator.

(water bubbling)
(tense music)

Ostracods, with their flash bomb defense,

are found throughout the world's oceans.

(waves lapping)

But in the Caribbean,
they employ their glow

to attract as well as to repel.

(boat motor whirring)

It's something that
researchers Gretchen Gerrish

and Trevor Rivers are studying,

the spectacular mating
display of ostracods.

But they can't even begin to
work until the moon is set.

- A fully moonlit night is not dark

in the eyes of an organism

that depends on their own
light that they create,

and so darkness truly
is just a starlit sky,

no moon present in the sky at all.

(diver grunts)

(water splashes)

(water bubbling)
(gentle music)

- [David] Diving without
torches in near total darkness,

Gretchen and Trevor are entering a world

that few people ever witness.

- [Gretchen] You're immersed in darkness.

You're immersed in water.

And you see streaming
stars floating past you,

and they're being produced
by these tiny crustaceans

that we barely understand.

- [David] By releasing small amounts

of glowing liquid as they swim,

male ostracods leave a trail
of lights in their wake.

The series of precisely
timed dots tell the female

where he will be in exactly half a second.

But as one male starts to display,

another and another join him.

(upbeat music)

- [Gretchen] And as they synchronize,

they fan out into this
firework like display of light.

(upbeat music)

It's one of the most awe-inspiring
things I've ever seen.

(upbeat music)

- With every research trip,

Trevor and Gretchen discover new species,

each with its own light language.

(upbeat music)

(bugs chirping)

Ostracods and fireflies
use bioluminescence

to find potential mates,

and it can be an efficient means

of getting your message
across, but it's not foolproof.

Those messages can be hacked.

There's a love cheat in this situation.

There's also a female of
a particular species here

that when she sees the males

of a different species fly past

answers with their particular call sign

and that attracts them.

And when they arrive,
instead of mating with them,

she has her own dastardly way with them.

(tense music)

She mimics the flash
patterns of other species.

An unsuspecting male is lured in.

(tense music)

Fireflies contain toxins

thought to protect them
against most predators.

But this femme fatale is not put off

and she eats him alive.

In fact, it may be the
toxins that she's after.

She can't produce such chemicals herself,

so she tricks and then devours males

of different species to obtain them.

(gentle music)

If she can't get males to come to her,

she goes after them.

And a good place to look for
one is on a spider's web.

(gentle music)

A male firefly is ensnared.

As the spider venom takes effect,

his thrashing turns to a constant glow.

(gentle music)

The femme fatale is
alerted by the dim glow

and she flies straight onto the web

to steal the spider's catch.

As the spider struggles to keep its prey,

she dazzles it with her lantern.

(bugs chirping)
(gentle music)

Using her light, the firefly

can clearly see the
spider and avoid the web.

(tense music)

The confused spider loses out.

(tense music)

(gentle music)

Predation turns out to be one area

where light making life
has been very creative.

(bugs chirping)
(gentle music)

Like a scene from the
surface of an alien planet,

these termite mounds have
lodgers living in their walls.

(thunder rumbling)
(gentle music)

The luminous larvae of click
beetles wait in burrows.

(tense music)

(bugs chirping)

Insects are drawn to their death

by the green glow, like moths to a flame.

And the beetle larvae gorge

on the steady supply of
unsuspecting victims.

(tense music)

(thunder rumbling)

These predators work as individuals.

There is another insect
that excels in deception,

but it works alongside
thousands of its own kind.

(water trickling)

From outside, this cave shows no sign

of the astonishing
things that go on inside.

(tense music)

The entrance is fringed
with a curtain of silk,

woven by the larvae of a kind of gnat.

They move back and forth along the rocks,

lowering sticky strings of
saliva from the roof of the cave.

(tense music)

As night falls, the walls
and ceiling of this cavern

become nature's very own planetarium.

(gentle upbeat music)

The trap is set.

The cool blue light,

produced in each larva's
tail, is the lure.

(gentle music)

Other insects that hatch
and emerge in the cave

instinctively fly upwards to the sky.

But this is not a starlit sky.

It's a death trap.

(tense music)

Bioluminescence is clearly a powerful tool

to these life forms that possess it,

but it's only effective in darkness.

Each dawn, the bright rays of the sun

overwhelm the power of living light.

(waves crashing)

(birds squawking)

For all of the wonders of bioluminescence

in the plains and woodlands of the earth,

there is one place where living light

is virtually the key to existence,

the world of eternal
darkness, the deep sea.

(waves crashing)
(gentle music)

The Western Flyer is one of the world's

most advanced deep sea research vessels.

In the black depths,

there are no edges, no
boundaries, nowhere to hide.

Predators and prey have
therefore had to develop

some extraordinary
strategies to stay alive,

and many do so with the help of light.

Dr. Steven Haddock has
spent the last 25 years

studying the least known
part of our planet,

the ocean depths.

(gentle music)

- I think people look at bioluminescence,

this ability to make light,

they think of it as a very magical thing.

But once you see the diversity

and the range of functions
that bioluminescence serves

for animals in the ocean,

it's clear that it's a critical part

of the whole ecology of the system.

- [David] Until recently,
it was all but impossible

to collect living bioluminescent
creatures from the deep.

But this remote submersible

known as the Doc Ricketts
is equipped to do just that.

They're trying to find new life

and clues as to why light making

has evolved in so many forms.

(tense music)

In the control room
thousands of meters above,

Steve and the crew navigate
past alien-like life forms.

- Nice.

Wow.

- [David] But in truth,

it is us who are the aliens down here.

(dramatic music)

Although very sophisticated,

the Doc Ricketts' own remote cameras

are not sensitive enough
to record bioluminescence,

so they use bright lights to
find and film these creatures.

To have any hope of observing
their light making powers,

the research team needs to
bring them to the surface.

Gentle suction and remotely
controlled canisters

are used to delicately scoop
up the rare sea creatures.

(gentle music)

Vampire squid.

- [Steve] Even with it in.

Down.

Yes!

- [David] Viper fish.

- [Scientist] That's it.

- [Scientist] Perfect.

(Steve laughs)

- Oh, look there!
- Oh!

- [David] And dragon fish.

They don't just sound like
something from a sailor's tale

of fantasy monsters.

They look like them too.

This is one of the few dragon fish

that has ever been seen alive,

and it's one of the even fewer

that have been captured unharmed.

(gentle music)

- Yes!
- Yay!

- Oh my gosh.
- Up and down 10.

(tense music)

- [David] Once they arrive on the ship,

thousands of meters above
their normal environment,

there is no time to waste.

The enormous pressure
change is likely to cause

any bioluminescence
abilities to disappear.

- [Scientist] One of
the cuts just appeared.

- [David] The race is
on to try and observe

those abilities and
understand their functions.

(gentle music)

- [Scientist] Wow.

(gentle music)

- In some species, it
seems to be defensive,

like the circling flashes
of the Atolla jellyfish,

or the rippling light waves
of the Beroe comb jelly.

(gentle upbeat music)

In other species, like this viper fish,

light is used not only for
defense but to lure prey.

(gentle upbeat music)

These pyrosomes, colonies of
minute translucent creatures,

use light to communicate
within the colony.

The team's experiment shows that

as one colony begins to glow,

its neighbors light up in response.

What could they be saying?

Thanks to the delicate sampling
methods of the Doc Ricketts,

the team are able to observe

a living and luminescent dragon fish,

a sight few have ever witnessed.

Whatever their function,

one thing unites all these
types of bioluminescence,

their other worldly beauty.

(gentle upbeat music)

And this beauty is the result
of an evolutionary arms race

where light is a weapon
to blind or deceive.

In response, some animals have evolved

the most sophisticated and
bizarre eyes on the planet.

The rare barrel-eyed fish has eyes

that can only look upwards

through the top of its translucent head,

searching for prey above.

It's so rare, catching
even a glimpse of it alive

is a huge achievement.

(gentle upbeat music)

And the same is true
for the cockeyed squid.

It has one normal eye and one
strange upward looking eye.

(gentle upbeat music)

At this depth, it is
too dark for human eyes,

but the faintest light from the surface

half a kilometer above can
just reach this twilight zone.

Firefly squid normally
live at these depths.

To prevent themselves from
being seen from below,

they hide themselves with light.

It's a strange paradox.

In this dark world,

light can be used for camouflage.

(gentle upbeat music)

At close range, the light emitting cells

called photophores are easy to see,

but from a distance, they break
up the outline of the squid

and it merges with the background.

(gentle upbeat music)

It's an elegant solution
used by many creatures

when a silhouette can be a death sentence.

(gentle upbeat music)

In shallower waters, the
color of the light changes,

so the squid, as it gets
closer to the surface,

uses green photophores.

(gentle upbeat music)

The lives of firefly squid are short.

When they're only a year old,

mated females make their final journey

to the surface to spawn.

(gentle upbeat music)

But even in their final moments,

they're both spectacular and valuable.

(gentle upbeat music)

All along the coast here, these squid,

which die naturally after spawning,

are gathered as a local delicacy.

It's largely through this fishery

that we know anything at
all about the firefly squid.

Like so many deep sea creatures,

their daily lives are
still virtually unknown.

What we do know is that
their world is dominated

by bioluminescence.

We've come a long way
from watching fireflies

in the woodlands of Pennsylvania.

Organisms that produce light
on land may be exceptional,

but in the sea, creatures that do so,

like these comb jellies,
are in fact the norm.

(upbeat music)

In the oceans and on land,

living creatures of many
kinds have harnessed

the power of light in extraordinary ways,

to mate, to lie, even to
hide under a cloak of light.

(dramatic music)

Yet, with the latest
cameras and technology,

we're only beginning to understand

the lives of luminous creatures.

There remain many mysteries,

but what a beautiful world they create,

and what a beautiful world

awaits the scientists of the future.

(dramatic music)

(water splashing)