Attenbobough's Life That Glows Page #2

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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.

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.

These lights are made by captives,

which are farmed in special organs below the eyes of flashlight fish.

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.

Just before they change direction, the fish give a quick blink.

These lights have other functions, too.

They act as headlights to illuminate the sea floor

as the fish search for food.

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

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.

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 by-product 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 appetising.

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 defence seems to be a common function.

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 are deadly poisonous.

Their bright colours are a clear message to predators -

"Do not eat me. I am laced with cyanide."

But what about millipedes that are active at night?

They are no less toxic than those that are active during the day.

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

Could it be that luminescence is a way

of warning off night-time 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 contain cyanide,

the light evolved a function.

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

But my eyes are not the eyes of a night-time 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.

This simple experiment produced a clear result.

Living light can act as a warning.

But proving the function of bioluminescence is not always

so easy, as a recent discovery has shown.

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 her 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 that's because few people went out in the middle of the night

digging a hole, especially without a light.

But eventually, science recognised these creatures.

But why should they luminesce in the darkness of the soil?

Nobody knew.

This blue light had gone unnoticed by science until 2010,

when biologist Marcel Koken first saw their eerie glow.

We are trying to find out why this animal produces light.

A thing living underground. Why produce light?

No use for it, apparently.

Is it just a by-product 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.

Marcel's experiments have shown that the worms can

control their brightness.

When the beetle touches part of the worm, its light gets brighter.

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

it lights up, that scares the predator.

The 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.

If this is defence, 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 produce their eerie light underground.

But there are rare occasions

when luminous life is all about revealing yourself.

May 2015.

While the southern aurora illuminates the night sky above,

the sea below produces a strange blue glow.

Each wave causes a ripple of intense colour.

The animals in the bay notice it first.

Wading birds are attracted to small crustaceans

caught in the glow.

Each movement alerts others to this rare spectacle.

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

That is amazing!

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

That's wicked.

LAUGHTER:

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.

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