Hi, my name's Raj.
You are listening to Sleep Tight Science.
Did you know that scientists estimate that about three quarters of deep sea animals can produce their own light?
What?
Light that comes from chemistry happening inside their own bodies.
Hello friends and welcome back to Sleep Tight Science a bedtime show that answers your questions about science.
In this episode, we have three questions from four different kids about exactly the same thing.
Autumn is 8 years old and lives in Canada.
Kyren is 5 years old and lives in Las Vegas, Nevada.
Virginia is 5 years old and lives in Massachusetts.
And Elliot is 7.
All four of them wanted to know about bioluminescence.
Bioluminescence is a bit of a mouthful.
Let's try to say it together.
Bioluminescence.
It means light made by living things, not by the sun or by a flashlight, and not by electricity, but by chemistry happening inside an animal's own body.
So we're going to find out how bioluminescence works, where it lives and what scientists have discovered by studying creatures that glow in the dark.
We'll go very deep into the ocean and we'll meet some of the most interesting living things on Earth.
A quiet thank you to Rush Rinaldi, age 8, in Irving, Texas, for introducing our show.
And to all our curious friends who send in questions.
You help us learn together.
Take a slow, deep breath.
Get comfortable.
And let's find out what glows in the dark.
Let's start with the word itself, bioluminescence.
Bio means life.
Luminescence means the production of light.
Put them together and you have something that sounds like it belongs in one of our Kai Kai and Boo Boo stories, but it is completely and wonderfully real.
Lights made by living things.
But how does a living thing make light?
Usually when we think of light, we think of the sun or electricity powering a lamp in your room.
In this case, It's all chemistry.
Inside the bodies of creatures that bioluminesce, from tiny ocean bacteria to deep sea fish.
There are two key ingredients that work together to make this happen.
The first is a molecule called luciferin.
The second is something called luciferase, which is an enzyme, a special molecule whose job it is to help chemical reactions happen faster.
When luciferin meets oxygen inside the creature's body and luciferase is there to help the reaction along something remarkable occurs.
Energy is released, and instead of becoming heat, that energy becomes light.
Both words come from the Latin word lucifer, which simply means light bearer.
The same root gives us the word lucid, meaning clear and bright.
These are ancient words for an ancient phenomenon.
Now, here is something that makes this even more impressive.
When a regular light bulb produces light, It also produces a tremendous amount of heat.
In fact, roughly 90% of the energy used by a traditional light bulb is wasted as heat.
Only about 10% actually becomes visible light.
Bioluminescence works almost the opposite way.
Most of the energy becomes light with very little heat produced.
Scientists call this cold light.
It is one of the most efficient energy processes found anywhere in nature.
Different creatures produce different colors of light, depending on the exact chemistry involved.
The most common color is blue-green, and there's a good reason for that.
Blue and green wavelengths of light travel much further through water than red or yellow wavelengths do.
In the deep ocean, blue-green light can be seen from a much greater distance, so the creatures most useful for that environment have evolved to produce exactly that color.
Some species produce red light, some yellow, and a few produce light in ranges human eyes can barely detect.
One of the most astonishing things about bioluminescence is how many times it has appeared in the history of life on Earth.
Scientists estimate that bioluminescence has evolved independently at least 40 separate times, meaning it didn't appear once and spread, but kept being invented over and over again in bacteria, in fungi, in plankton, in jellyfish, in worms, in fish and in many other creatures.
When something keeps evolving independently across such different forms of life.
That tells scientists something important.
It works.
It is so useful in so many situations that life keeps finding its way back to it.
We did touch on bioluminescence briefly in our jellyfish episode, but tonight we go much deeper.
Because the science behind living light is one of the most interesting stories in all of biology.
And four curious listeners from Canada Nevada, Massachusetts and somewhere else in the world thought you should know about it.
So now we know how bioluminescence works.
But where does it live?
And why do creatures use it?
The answer to the first question takes us somewhere most humans will never go.
The ocean covers more than 70 of the Earth's surface, and most of it is deep, far deeper than sunlight can reach.
Below about 200 meters or roughly 660 feet, sunlight fades quickly and deeper still later.
Darkness becomes complete.
Below that line, it is permanently, absolutely dark.
And yet life is everywhere down there.
Extraordinary, strange, patient life.
And much of it glows.
This is the world Kyren and Virginia are asking about.
How does bioluminescence work inside a fish's body?
To answer that, let's talk about the anglerfish.
The female anglerfish is one of the most recognizable deep-sea creatures on Earth, partly because she looks like something from a nightmare and partly because her fishing technique is genuinely brilliant.
Growing out of the top of her head is a long spine, and at the very tip of that spine hangs a small glowing lure.
It pulses softly in the darkness.
Small fish and other creatures drawn toward the light swim closer and straight into the anglerfish's waiting jaws.
But the anglerfish doesn't actually make that light herself.
She can't.
The glow comes from millions of bioluminescent bacteria living inside the lure.
The anglerfish provides the bacteria with a safe, warm home and nutrients to survive.
The bacteria provide the anglerfish with light.
Scientists call this kind of arrangement a symbiotic relationship, where two different creatures live together and both benefit.
The anglerfish and her bacteria have been working together this way for millions of years.
Other creatures carry their light differently.
The firefly squid found in the waters around Japan is covered in tiny light-producing organs called photophores, which it can control individually flashing patterns across its body.
One use is communication, signaling to other firefly squid in the dark.
Another is something called counter illumination.
From below looking up toward the faint surface light.
A creature swimming overhead casts a dark shadow easy for a predator to spot.
By producing light on its underside that matches the faint glow from above, the firefly squid erases its own shadow and effectively disappears.
Camouflage made of light.
And then there are the dinoflagellates tiny single-celled organisms, each one invisible to the naked eye, that float in their billions near the ocean surface.
When they are disturbed by a wave, a swimming hand, the bow of a boat, they flash blue-green light.
In places where dinoflagellates gather in large numbers, the ocean itself seems to glow.
Waves breaking on a beach at night sparkle blue.
A swimmer's arms leave trails of cold fire in the water.
It has been described as one of the most magical sights in the natural world.
So creatures glow to hunt, to hide, to communicate, and to disappear.
Four different problems with one amazing solution.
And much of it happening in a part of the ocean most people never think about.
In permanent darkness, very far below.
Elliot asked about bioluminescence in the broadest way, just the word itself and everything it contains.
So this last part is for Elliot.
The biggest question of all.
Why does any of this matter beyond the deep sea?
It turns out that living light has quietly changed the course of modern medicine.
In the 1960s, a marine biologist named Osamu Shimomura was studying a small, unremarkable jellyfish called a crystal jellyfish, found off the coast of the Pacific Northwest.
He wanted to understand why it glowed.
After years of patient work, he isolated something unexpected a protein that fluoresced bright green when exposed to ultraviolet light.
He called it green fluorescent protein, or GFP.
At the time, it seemed like a curiosity, an interesting fact about a small jellyfish.
Nothing more.
Then other scientists realized something.
If you could attach GFP to other proteins inside a living cell, those proteins would glow.
You could watch them move.
You could track them in real time inside a living body without disturbing anything.
For the first time in history, scientists had a way to see inside the machinery of life as it was actually working.
The implications were enormous.
Researchers began using GFP to watch cancer cells divide and spread, to track how viruses move through the body, to study how the brain forms memories and to understand how diseases develop at the cellular level.
Osamu Shimomura and two colleagues were awarded the Nobel Prize in Chemistry in 2008 for this discovery.
A jellyfish that glows in the Pacific Ocean, helped unlock some of the deepest secrets of human biology.
And there is still so much left to find. much of the deep ocean remains unexplored.
The creatures living there, many of them glowing, many of them unknown to science, are waiting.
Every research expedition into the deep sea returns with species nobody has ever seen before.
Some of them will almost certainly have things to teach us.
Now for some fun facts about living light.
Did you know that fireflies are remarkably efficient?
Their light is produced with almost no heat at all.
Scientists estimate their bioluminescence is close to 100% efficient.
Compare that to a traditional light bulb, which wastes most of its energy as heat.
Engineers have actually studied firefly lanterns to design better LED lights.
There are approximately 100 known species of glowing fungi, mushrooms that produce a faint, eerie light in the dark.
Scientists are still working out exactly why.
Did you know that the cookie cutter shark has bioluminescent markings along most of its body, with one dark patch near its throat that from below, looks like a small fish?
Larger predators investigate and find a cookie cutter shark instead. a glowing disguise.
Bioluminescent bays exist in a handful of places around the world, including Puerto Rico and parts of Vietnam, where concentrations of glowing dinoflagellates make the water light up with every movement.
People kayak through them at night.
The first bioluminescent organisms appeared on Earth approximately 540 million years ago, long before dinosaurs, long before flowers, long before almost everything we recognize as familiar life.
And finally, some sea turtles can fluoresce.
They absorb blue light and re-emit it as green or red.
In 2015, Researchers photographing coral reefs at night discovered that hawksbill sea turtles were absorbing blue light from bioluminescent organisms around them and re-emitting it as green and red.
In this episode we heard from four curious listeners Autumn Kyren, Virginia and Elliot, who all wanted to know about bioluminescence, the remarkable ability of living things to produce their own light.
We learned about the chemical reaction between luciferin and luciferase that makes cold light possible and why bioluminescence is one of the most efficient energy processes in nature.
We went into the deep ocean to meet the anglerfish and her glowing bacterial partners, the counter-illuminating firefly squid and the dinoflagellates that turn ocean waves electric blue.
And we discovered how a small Pacific jellyfish changed the course of modern medicine and why the darkest parts of the ocean may still hold the most remarkable discoveries of all.
Here's a wave to some of our question askers.
Kenneth, six years old from San Jose, California.
Regan, seven years old from Melbourne, Australia.
Amelia, age seven, from Madison, Wisconsin.
Franklin, seven years old, in London, Ontario.
Emma Tao, eight years old, in Shanghai, China.
Killian.
Ruth Miser.
Maddie, seven years old, from Quaterio, Mexico.
Dominic, age 5, and Annie, age 2, from Medford, New Jersey.
Alyssa, age 5.
Harrison, 6 years old, from Castle Rock, Colorado.
Otis, 4 years old, from San Diego, California.
Piper and Otto, from Harrisburg, Virginia.
Heidi, age 5, and Peter, age 2, who live in Kentucky.
And Lori, age 6.
Thank you for asking questions that spark our curiosity and keep us learning.
To submit your questions.
Ask your parents to help you.
Write us a note to the email address in our episode notes.
You can also visit our website and send a message that way.
Also don't forget to leave us a review.
It helps other people find our show.
Did you know your brain can go on amazing adventures when you sleep?
Tonight you might dream about some of the incredible things we talked about, like sinking slowly into a warm, dark ocean, watching the water around you begin to glow blue and green with every movement you make.
Maybe you'll imagine yourself as a deep sea scientist, lowering a camera into the darkness for the first time and watching the screen fill with creatures that pulse and flicker and flash.
Things nobody has ever named.
Things nobody has ever seen.
Maybe you'll dream of swimming alongside an anglerfish, watching that little lure glow and sway in the deep, or floating through a bioluminescent bay at night, every stroke of your arms leaving trails of cold blue fire in the water behind you.
Whether you're watching dinoflagellates spark like tiny stars beneath the surface, tracking a glowing sea turtle through a coral reef, or holding a crystal jellyfish in your hands and watching it shimmer green, your dreams can take you anywhere the light goes.
Who knows?
Maybe tonight you'll dream of finding something in the deep that nobody has ever found before.
And maybe, just maybe... you'll wake up with a question nobody has ever thought to ask.
And from our little corner of the world, we're glad you spent this time with us.
From Cheryl and Clark, good night, sleep tight.
