On a summer’s night, there’s nothing more magic than watching the soft glow of fireflies switching on and off. Few other life forms on land can light up the night, but in the dark depths of the oceans, it’s a different story: nearly 90% of all species shine from within. Whether it’s to scare off predators, fish for prey, or lure a mate, the language of light is everywhere in the ocean depths, and scientists are finally starting to decode it. NOVA and National Geographic take a dazzling dive to this hidden undersea world where most creatures flash, sparkle, shimmer, or simply glow. Join deep sea scientists who investigate these stunning displays and discover surprising ways to harness nature’s light—from tracking cancer cells to detecting pollution, lighting up cities, and even illuminating the inner workings of our brains.
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Creatures of Light
PBS Airdate:February 3, 2016
NARRATOR: They're some of the most dynamic, dazzling, jaw-dropping displays in nature.
EDIE WIDDER (Ocean Research & Conservation Association): It's these rocket ships and explosions of sparks and spewing of what looks like blue smoke. And these long chains look like Japanese lanterns, extending off into the distance, as far as you can see. It's magic.
NARRATOR: Some flash, some sparkle, others simply glow. But most, we're only beginning to discover.
VINCENT PIERIBONE (John B. Pierce Laboratory): Suddenly, we recognize it, and now we find it everywhere under there.
NARRATOR: Hidden in the deepest, darkest, most remote stretches of our planet, these luminous critters can be timid performers. But the closer we look, the more we realize the light they create is pervasive.
JOHN SPARKS (American Museum of Natural History): If it wasn't important to the organisms, you wouldn't see it all over the tree of life.
NARRATOR: Now, scientists are thrusting these cryptic creatures and their fantastical displays into the limelight. Some are even attempting to harness this light, co-opting millions of years of evolution for the betterment of our own dim species.
DAVID GRUBER (National Geographic Emerging Explorer): We have to go to the ocean to find these animals that give off light, so that we can then understand ourselves. To me it's a beautiful connection.
NARRATOR: We're shedding light on the Creatures of Light, right now, on this NOVA/National Geographic Special.
It's one of life's essential ingredients. We soak up its energy, set our clocks by it, need it to see. Light is so precious to us humans, we've coaxed it into lasting all night long.
But imagine a world without it.
While we're cursing the darkness, countless thousands of other species have evolved a much brighter response, without burning an ounce of fossil fuel. It's called "bioluminescence," living light. And from glowworms and fireflies to plankton and jellyfish, it's been lighting up the dark for hundreds of millions of years.
JOHN SPARKS: If you look across the tree of life, essentially, bioluminescence is splattered all over it.
EDIE WIDDER: It's just everywhere you look. How to survive in the dark? Make light!
NARRATOR: On land, where it's dark only at night, just a fraction of creatures evolved the gift of glow, but descend into the deepest depths of the oceans, where the bulk of Earth's creatures reside, and you find a very different story. Down here, as many as 90 percent of lifeforms shine.
DAVID GRUBER (Marine Biologist): I'm going to come off the wall and head out into open water.
Surface, surface, this is Nadir. Our present depth is approaching 100 meters, life-support okay.
NARRATOR: That's why a team of scientists from New York's American Museum of Natural History is here, plying the dark waters of the South Pacific Ocean in search of new luminescing creatures.
DAVID GRUBER: I'm going to start motoring away here.
NARRATOR: They've journeyed to the other side of the world to the pristine and remote waters of the Solomon Islands to unravel how and why light-producing animals evolved, and perhaps, put their living light to work for us.
David Gruber is a marine biologist.
DAVID GRUBER: After about 100 meters in the ocean, you get into this twilight zone. About one percent of light gets down. So, as you start getting deeper, you'll start seeing almost everybody down here, every fish that we see down here has this ability to blink or flash or communicate, producing its own light.
NARRATOR: The problem is, common as bioluminescence may be down here, it's challenging to study, even with a submersible. The water is too dark, the distances are too great, and the light the animals give off is too unpredictable.
It's a tough environment for marine biologists to work in, but a neuroscientist, like Vincent Pieribone, feels especially out of his depth.
VINCENT PIERIBONE: I'm a scientist that spends most of my time in a laboratory. So, it's very scary, to be completely honest with you. You have to keep your head and your wits about you, and try to focus on what the job is, not really think about the fact that there's, you know, a few tons of water on top of us, at the moment. So, but we're here for…in the name of science, so we press on.
DAVID GRUBER: Ooh. That's a photophore.
NARRATOR: One goal for this trip is to develop a better low-light camera. Deep-sea bioluminescence has only been filmed in the wild a handful of times. Most of what we know comes from observing animals in carefully lit tanks on the surface. Whether it's the infamous anglerfish, with its luminous lure, or the light-packed viperfish, one of the deep's most ferocious predators, scientists typically collect them in small trawl nets, like these.
JOHN SPARKS: You're going to turn around the net, right? All right, thanks!
NARRATOR: They then examine their unique light-producing organs to infer how they work. That's what biologist John Sparks is trying to do with this viperfish. They may be fierce but even the big ones are actually pretty small.
JOHN SPARKS: This is a monster for these things. There are a bunch of different species. They're hard to tell apart. I've actually never seen one that big.
We still know so little. That is what is kind of frustrating. You've got to get the organisms up alive, which is tough. You've got to be able to image enough different species to make it meaningful, but in terms of us doing anything scientific with it, it is very tough, because we got so little data.
NARRATOR: What scientists want to understand is how luminescent features became so pervasive in the deep ocean. And why, in a world full of predators, would animals invest so much energy into lighting up, and standing out, in the first place?
They are questions marine biologist Edie Widder has been grappling with for decades. An expert on living light, she was among the first to study it under water.
EDIE WIDDER: I wish I could describe what it is like to be down there, because I would like people to be able to appreciate it the way I have. It's these rocket ships and explosions of sparks, and spewing of what looks like blue smoke, and these long chains of cyphonophors, that are like chains of jellyfish, that look like Japanese lanterns, extending off into the distance, as far as you can see. It's magic.
NARRATOR: Edie devised her own methods to trigger these underwater light shows. She mounted a large screen on the front of her submersible. When creatures bump into it, they light up, and her low-light cameras record them in the act. Over the years, the aptly named "splat cam," has helped bring to light some of the most bizarre creatures in the deep, everything from jellyfish to sea cucumbers.
EDIE WIDDER: The open ocean is the biggest living space on our planet, by far, and it is a very unusual environment. There's no trees or bushes to hide behind, but animals have to play all the same games of hide and seek that animals do on land, and that is where bioluminescence comes in.
NARRATOR: In this deep, dark abyss, light, it seems, is vital, and creatures have evolved to wield it in many different ways for many different reasons. Tiny organisms called dinoflagellates, for example, alight in unison whenever the water around them is disturbed, taking the shape of whatever swims through them. It's a treat for the lucky few who get to bask in their soft glow, but for predators of these microbes, like shrimp, it's more like tripping a motion sensor. Every time they make a move, the lights come on and give away their location. Predator becomes prey to a host of other creatures, like cuttlefish.
But some shrimp are armed with their own light-filled defenses. When threatened, certain species shoot bright flashes of light to stun and confuse their enemies.
EDIE WIDDER: There's a lot of animals that actually can release their luminescence that way. So, you can have something like a shrimp that will spew luminescence out of its mouth like a fire-breathing dragon and temporarily blind its predator, while it pulses away into the darkness.
NARRATOR: Rather than blinding their predators, a huge variety of fish, from squid to sharks, use light to hide from them. It's called counter-illumination, and it may seem counterintuitive, but consider how a fish swimming near the surface appears to a predator in the depths below. As sunlight or moonlight beams down on them, their silhouettes are plain as day.
EDIE WIDDER: And so an enormous amount of animals in the ocean produce bioluminescence, from their bellies, that exactly matches the intensity and the color of the sunlight coming down through seawater.
NARRATOR: When the lights come on, the animals vanish.
EDIE WIDDER: It is an amazing cloaking device. They just disappear, utterly disappear.
NARRATOR: Others, like ostracods, tiny shrimplike critters, use light a bit more extravagantly. They ooze light to stand out and impress the opposite sex.
EDIE WIDDER: Ostracods, which are about the size of sesame seeds, produce a crazy amount of light, for such a little organism. And they'll squirt out one little dot, and then they swim a little further and they squirt out another dot, and another dot, and another dot. And the spacing of the dots is species-specific. And so, the female can recognize the male that she can mate with. So, it's almost like skywriting, but it's light-writing. It is beautiful.
NARRATOR: But mates aren't the only creatures light attracts. Many fish use light to lure food in, as does the most notorious bioluminescent creature of all.
ALBERT BROOKS (Voice of Marlin in Finding Nemo/Film Clip): What is that?
ELLEN DEGENERES (Voice of Dory in Finding Nemo/Film Clip): It's so pretty.
EDIE WIDDER: Remember that ugly angler in Finding Nemo?
ALBERT BROOKS (Voice of Marlin in Finding Nemo/Film Clip): Good feeling's gone.
EDIE WIDDER: That lure is actually meant to attract another fish or another little shrimp that comes to gobble it up and then finds itself engulfed in this living mousetrap of needle-sharp teeth.
NARRATOR: Lures, motion sensors, cloaking devices, all together, bioluminescence lights up the deep, like an aquatic Times Square.
DAVID GRUBER: Bioluminescence was a tool that was laying out there, and somebody was like, "I can use it for this," and somebody's like, "Well, I can use it for that."
JOHN SPARKS: They use it to find food; they use it to avoid being eaten; they use it for mating; and they use it to communicate with each other, just like all these signals are trying to communicate with us; things that are very important to, not only the individual, but the species, as well.
NARRATOR: Despite all the risks, light is a shining example of Darwin's theory of evolution. From bacteria to jellies to fish, it helps organisms survive. But the question remains, how did the initial spark for this light arise?
To find out, scientists have turned to a different set of bioluminescent creatures, ones that are a bit more familiar and easier to study.
Land critters have evolved their own special ways of using light. Take the glowworm, for example. Like anglerfish of the deep, thousands of these fly larvae light up the roofs of these caves, in New Zealand, like the night sky, to lure in a meal. The starry ceiling fools prey like flies and moths, which are attracted to the light. As they fly upwards, they get trapped by the glowworms' sticky, threadlike snares.
Rather than luring prey in, other bioluminescent creatures, like this millipede in the Sierra Nevadas, use light as high-voltage signs to keep predators out. The bugs are laced with cyanide. Their nuclear glow alerts potential predators to leave them alone.
And then there are probably the most familiar displays of all. The brilliant flashes of fireflies are some of the most sophisticated mating strategies ever evolved, the ultimate in romance languages. By triggering a chemical reaction in their abdomens, male fireflies can turn themselves on or off on cue. And if they do it just right, they'll turn on female fireflies, too.
University of Florida biologist Marc Branham has devoted the last 15 years to deciphering this elaborate language of love.
MARC BRANHAM (University of Florida): It's like breaking the code.
NARRATOR: A secret code that has two parts.
MARC BRANHAM: If you actually measure these flash patterns very, very carefully, there are some features that are always standardized. And we think those are the parts of the signal which say, "I am a member of the following species."
NARRATOR: One of the 2,000 different species of firefly, which are actually not flies at all; they're beetles.
MARC BRANHAM: There's also parts of the signal that have a lot of variation across individuals.
NARRATOR: This second set of flashes is personalized. The timing differs from fly to fly within a given species.
MARC BRANHAM: Males are telling females, "I am a member of this species," but also "here is a little bit about me." It is the females who actually make the choice. They can see all these males flying around, flashing, and they see lots of variation in those signals. And some are more sexy than are others, and so those males get a flash response, by the female.
NARRATOR: Thanks to their enormous eyes, shaped over the eons to detect faint light, the males see the response and home in on the female's location.
MARC BRANHAM: He will flash back to her, she will flash back to him, and they will have a short dialogue, until the male finds out where she is, exactly. And he will land right beside her. It is Valentine's Day.
NARRATOR: It's the equivalent of strutting tail feathers, or chirping and croaking. To succeed in the reproduction game, you've got to make yourself known, and light is an effective way to cut through the chatter.
MARC BRANHAM: I mean, how can you miss a flash on a hot summer night?
NARRATOR: So how do fireflies and everything else that lights up, both on land and at sea, produce these brilliant flashes? It turns out, the luminescing beetles were the torchbearers for finding that out. In 1885, a French biologist, working on a firefly cousin called Pyrophorus, deciphered the chemistry responsible for their magical glow. He determined it's the result of a reaction between two chemicals, which he named for the fallen angel, Lucifer, the "light bearer."
One chemical, luciferin, acts as the fuel, kind of like gasoline. The second, luciferase is an enzyme, which fires the reaction, like a spark plug. When the chemicals are mixed together in the presence of oxygen and some other key ingredients, they react, and the excess energy is given off as light.
Over the last century, this light-producing reaction has been discovered scattered across the entire natural world, both above the surface and beneath the waves. That's how readily available these ingredients are.
The actual chemicals differ from creature to creature, but the basic mechanism of fuel and spark is the same, from flies and worms, to jellies and fish, to snails, even mushrooms. The reaction is so common, it has evolved independently, on different branches of the evolutionary tree, more than 40 separate times.
JOHN SPARKS: You find it from single-celled bacteria, up through things like starfish, jellyfish, up through the vertebrates, fishes. It's evolved so many times in so many different lineages. I mean, if it wasn't important to the organisms, you wouldn't see it all over the tree of life.
NARRATOR: When it comes to the survival of a species, nothing holds a candle to light.
But living light turns out to come in a variety of flavors, and back on their ship in the Solomon Islands, the scientists from the American Museum of Natural History are now preparing to study an altogether different type. Unlike the bioluminescence of the deep, this second kind, found in shallower waters, doesn't produce light of its own. Rather, it absorbs light from an outside source, soaks in its energy, and spits it back as a different color. It's called biofluorescence, and anyone who's ever danced under a black light or watched fingerprints light up on a crime show is familiar with the concept.
Fluorescent chemicals absorb light in a unique way. Down at the atomic level, light jolts electrons into more energetic orbits around the nucleus. When they fall back to their original state, a few billionths-of-a-second later, the electrons re-emit, or fluoresce, the light back, at a lower energy level, giving off a different color.
Fluorescent animals work the same way, only their special chemicals, typically fluorescent proteins, are built into their skin and other tissues.
VINCENT PIERIBONE: Biofluorescence is an odd property, because the animals don't actually produce any light. You shine one color of light, and they will produce a second color of light. And it is a pretty rare phenomenon.
NARRATOR: That's because, unlike bioluminescence, biofluorescence requires a special set of conditions to occur in nature. It needs sunlight to make light, but not sunlight as we know it up on the surface.
When it hits Earth, sunlight contains all the colors of the rainbow, as light going through a prism reveals. Each color is the result of a different wavelength of energy. But once the light hits water, things get interesting. Water acts like a filter, and the different wavelengths are only able to penetrate to certain depths. Long wavelengths like reds and oranges, fade out first, then yellows and greens, and then finally, a sea of blue. And, this pure blue light turns out to be the perfect trigger for fluorescence.
VINCENT PIERIBONE: So, they take the blue light that is coming to them in the ocean, and they convert it to greens and reds, and that gives them this color, this contrast.
NARRATOR: Depending on their chemical composition, different fluorescent proteins give off different colors, all of which can be hard to see. Without special filters, visible light can wash it out. That may explain why it's gone unnoticed for so long.
How animals use fluorescence is still a mystery. In corals, where fluorescence seems to be the most prevalent, it may be used as a kind of protective sunscreen, deflecting harmful U.V. light or absorbing dangerous byproducts of photosynthesis.
VINCENT PIERIBONE: So, the coral is this piece of rock with a skin coat of a few cell layers on top. And, in that layer, it's packed with this fluorescent protein. These animals are doing a lot of work to produce a lot of this protein. So that's the mystery: why are they doing it?
NARRATOR: For years, fluorescence was thought to be confined mainly to corals and some jellyfish, but recent finds reveal it may be much more widespread.
And in 2012, while shooting a mosaic of fluorescing corals off the Cayman Islands, David Gruber and John Sparks had a big "eureka" moment.
DAVID GRUBER: It's like 10 o'clock at night, we're diving on the coral wall, we're about 80 feet down. We're photographing lots of little montages of a coral reef, and we stitch it together, and when we got back to our lab at night and we're looking through our photographs, and there it is: like this bright green fluorescent eel in one of our photographs.
NARRATOR: It was the first time they'd ever seen a fluorescent fish in the wild.
JOHN SPARKS: We said, "What the heck is that?" And we thought it was a joke, that the guy, the photographer with us had Photoshopped something and was just playing with us.
JOHN SPARKS: No, no.
DAVID GRUBER: I'm turning this light up.
We didn't believe it at the time. We just checked our lenses. We thought it was some kind of glitch in the camera. Essentially, we got photobombed by a reclusive green fluorescent eel.
JOHN SPARKS: We get in on these guys, down here?
NARRATOR: The eel opened up a whole new world for the scientists.
DAVID GRUBER: Keeps turning it on.
NARRATOR: Armed with blue lights and yellow filters, the team started seeking out fluorescence closer to home, in aquariums.
DAVID GRUBER: Hey, this guy right here.
NARRATOR: They found it everywhere, all the way up the food chain…
JOHN SPARKS: Man, check that out.
NARRATOR: …in seahorses, rays and even some sharks.
DAVID GRUBER: Ah, pretty good.
JOHN SPARKS: Good. You get it?
I saw the shark glowing like crazy.
NARRATOR: All have been hiding their true colors in plain sight.
JOHN SPARKS: Whoa, there it is, the fluorescent one. Look at it. You can see it from here.
We are kind of looking back and going, "Why didn't anybody see this?" And, you know, you probably just think it is a bright fish, right? You don't know it is fluorescing, until you start looking. Once you start looking, then it is all over the place.
NARRATOR: To find out how prevalent fluorescence is, the scientists needed to move beyond aquariums and study it in the wild.
DIVER: There's a lot of nice…I just kind of cut into the reefs.
JOHN SPARKS: These little guys are gobies, or blennies. What's nice about these guys is almost all of these little groups are fluorescent, really fluorescent. These fish, here, look exactly alike, but they're all different species, so… And if you put them under fluorescent light, they look really distinct.
NARRATOR: In the monotonous, blue underwater world, the fluorescent splotches and stripes may act as secret barcodes, signaling fishes' identity to potential mates.
It's an idea made even more compelling, when scientists look closely at the fishes' eyes. Unlike human eyes, many fluorescent fish seem to have built-in yellow filters. The filters block out the ambient blue in the water, letting the vibrant colors of fluorescence stand out. This world, that's been hidden to us, may be plain as day to the fish.
DAVID GRUBER: The coral reef is one of most competitive environments in the world, it's one of the most biodiverse, everybody's fighting for space, so by having this ability to fluoresce, they're creating a richer world for them. And now we're, for the first time, we're beginning to see this world that they've been seeing for millions of years.
VINCENT PIERIBONE: Yeah, let's test it. Bring in the patient.
NARRATOR: For neuroscientist Vincent Pieribone, the discovery of new fluorescent animals is particularly exciting.
VINCENT PIERIBONE: Impressive. Wow, it's brilliant, brilliant.
NARRATOR: He's especially interested in the proteins that make the fish fluoresce. He's hoping to use them to light up living nerve cells and ultimately, map the human brain.
VINCENT PIERIBONE: The inside of the brain is a black box. It's probably the most amazing instrument on the entire earth. Nothing else comes close to the ability of the human brain. And yet we don't have even a very thin understanding of how it works. So, we have been in the ocean looking for proteins that we can put into nerve cells, so that those nerve cells glow. And we interpret that information and find out how the brain is doing what it does.
NARRATOR: Scientists use fluorescent protein to light up the inner workings of cells. The initial work began with a green fluorescent protein or G.F.P., which was initially isolated from this jellyfish.
DAVID GRUBER: Green fluorescent protein is like a little bicycle reflector that you could tag on to any protein, and then you'll watch, in real time, that protein moving about the cell, in a living cell.
NARRATOR: To do it, scientists take the gene that carries the recipe to make green fluorescent protein and then insert it into cells. Once the genetic instructions are inside, the cells make the protein. When scientists hit the organisms with blue light, the targeted cells fluoresce green.
DAVID GRUBER: So this revolutionized our ability to see, at the protein level, inside living cells.
NARRATOR: G.F.P. was a Nobel-Prize-winning discovery, bringing to light everything from the way cancer spreads—these are malignant cells travelling through blood vessels—to how viruses infect and replicate.
Here is H.I.V., the AIDS virus, spreading from one cell to another.
If scientists attach G.F.P. to virus-resistant genes and insert them into the D.N.A. of animals like mice and cats, they can even assess potential cures for AIDS, lighting up entire creatures in the process.
VINCENT PIERIBONE: So G.F.P. was a beautiful discovery. It allowed people to see cells in green. It makes, essentially, what is completely invisible, visible.
NARRATOR: Scientists have since manipulated G.F.P. to fluoresce different colors, enabling them to tag different cells at once.
VINCENT PIERIBONE: Very green.
DAVID GRUBER: Yeah, it's beautiful.
NARRATOR: They've also gone beyond that, mining the deep for new fluorescent proteins and finding colors across the light spectrum. But human brain tissue presents a unique challenge. It's quite dense, and none of the colors discovered so far can easily pass through it, so neuroscientists, like Vincent, have been looking for colors with longer wavelengths, like far reds and infrareds that can.
VINCENT PIERIBONE: Reds are a little bit better. They go a little bit deeper, but infrared will pass all the way through the tissue. So, for neuroscientists, the Holy Grail has always been as far red as possible.
DIVER: Exactly. Got it!
VINCENT PIERIBONE: So, getting these things out of the ocean is really key. It is the only place they have ever been really found, and we are back here again looking for ones with different colors, different intensities. So, that is our mission.
NARRATOR: To find the glowing creatures Vincent needs, the team dives at night, when there is no natural light to obscure their vision.
DAVID GRUBER: We are getting ready for a scoping mission, looking for biofluorescence out here on the reef. And we're going to be using this camera.
NARRATOR: To stimulate fluorescence, they'll shine blue lights that match the blue found underwater during the day and look through yellow filters, just like the ones the fish see through, to block out the blue light they're shining.
DAVID GRUBER: So, this way, we can be sure that everything we see in here, the different critters that we're looking at, are truly biofluorescent.
VINCENT PIERIBONE: Ready to roll?
NARRATOR: The divers have to get pretty deep, about 100 feet down, approaching that special zone that during the day is awash in blue, the most likely spot to find fluorescent animals. The reef is dramatic, even under blue light, but when the team looks through their filters, a different world comes into view, a technicolor dreamscape.
Vincent and David scan the reef for novel sources of fluorescence.
VINCENT PIERIBONE: We look around in the reef, and we swim around, and we identify something. Everything looks black, except those animals that are sending light back at us. And there's coral, and there's crinoids, and there's anemones, and there's fish, all giving this back. And I can take a tiny piece of a single animal, or tiny part of an animal, and you can sequence an entire genome. Now you have everything you need to know about the animal, genetically.
NARRATOR: They're especially interested in glowing, red animals, and there's no shortage of them down here. But not all red animals are useful. Some depend on multiple proteins to produce the color, making them too complicated to study the brain. To hedge their bets, they grab as many interesting samples as they can.
SCIENTIST 1: Top of the evening to you.
SCIENTIST 2: Hey, mate, you want to kill the engine for me?
SCIENTIST 3: Some friends out there, huh?
SCIENTIST 1: Yeah, it's really sharky out there tonight.
SCIENTIST 3: This one, this thing right here, the leafy thing right here, unbelievable. You see it? Like a Christmas tree.
SCIENTIST 1: And I got another one of these guys.
SCIENTIST 3: Let's get them back and look at them.
SCIENTIST 1: Yeah, that was unbelievable.
NARRATOR: Back at the ship's lab, the scientists anxiously examine their catch, once again simulating the ocean blue with their special lights, and peering through their yellow filters.
SCIENTIST 3: And this is what? This is the soft coral, right?
So, let's go through here.
Oh, my goodness, it's very nice.
NARRATOR: Anything promising gets a closer look under the microscope.
SCIENTIST 1: What is it? It's crazy. You think it's a coral?
SCIENTIST 3: No, and it's only on small… I wish this boat wasn't shaking so much. Somebody radio up.
SCIENTIST 1: Somebody radio up to stop moving the boat.
NARRATOR: Not everything they collect turns out to be fluorescent.
SCIENTIST 1: Nothing. It's not fluorescent at all. No. Not a single bit.
NARRATOR: They do isolate several interesting green specimens, photographing and freezing away each one. And then, finally…
VINCENT PIERIBONE: There you go!
VINCENT PIERIBONE: That's beautiful. That's the red fluorescent protein we're hunting for. We're shining blue light on it, but what you're getting is red light coming out. So that's the whole, that's the trick to fluorescence.
Check that out. Whoa! Looks like fire.
NARRATOR: The scientists won't know if they can isolate the red fluorescent proteins, until they get back to their labs, onshore. Even if they can, it's still a longshot, whether they can turn them into useful probes to study the brain.
VINCENT PIERIBONE: I'm getting pumped up now. Look at that.
Good stuff. Isn't that awesome?
NARRATOR: But for now, this is as close to success as they allow themselves to hope for.
VINCENT PIERIBONE: Science must march forward!
NARRATOR: Back in New York, John Sparks and David Gruber rescue their samples from the deep freeze at the American Museum of Natural History and begin the painstaking process of carefully examining each of their hundreds of fluorescent specimens.
From one eel, just a few years ago, the scientists have now discovered fluorescence in more than 200 species of fish.
JOHN SPARKS: Biofluorescence is found all over the tree of life, just like you see for bioluminescence, just like somebody took it and threw it at the tree, and kind of stuck it in certain places, no clear pattern to it.
NARRATOR: Now it's a matter of extracting the proteins from the diverse creatures, starting with a bit of tissue.
DAVID GRUBER: We only want to isolate the little bit of the tissue that is fluorescent and nothing else.
Here to here.
LAB TECH: Yeah.
DAVID GRUBER: Perfect. Now, let's go into here.
NARRATOR: From this, they isolate the genes that make the proteins causing the critters to fluoresce, and then send any promising targets off to Vincent.
VINCENT PIERIBONE: This is exactly how the plates should look, nice and distributed. They should be far enough apart.
NARRATOR: At Yale, Vincent and his colleagues try to turn them into tools to understand the brain. Using genetic engineering, they fuse the fluorescent proteins to others that are sensitive to voltage, the language of brain cells.
VINCENT PIERIBONE: So, that'll run for an hour.
LAB TECH: Okay.
NARRATOR: They've recently done this with green fluorescent protein and fruit fly brains, which are less dense than ours.
VINCENT PIERIBONE: So we need a protein that can go from dim to bright very quickly, up, down, up, down, to be able to follow these rapid transitions in electrical signals that we see in a cell.
NARRATOR: They then insert the glowing, voltage-sensitive protein into the flies. Under a special microscope, they can now watch as the flies think. Each time a neuron fires, the voltage changes, and so does the intensity of the glow.
VINCENT PIERIBONE: To be honest with you, it is absolutely exciting to sit there and see a brain of an organism as the animal is thinking, and watching it, as it happens, in real time.
NARRATOR: Unlike conventional scans, which measure activity across the entire brain, these flashes of light and color are some of the first direct images of electrical activity of individual neurons in a living, thinking brain, the basis of all behavior.
Here's a fly being presented with a new smell…when going to sleep…when waking up.
So far, the scientists have managed to image just a handful of neurons, a far cry from the 86-odd-billion powering the human brain. But to Vincent, it's a profound step on the way to decoding how our brains govern our actions and conjure our thoughts.
VINCENT PIERIBONE: Ultimately, that nerve cell activity is what gives us consciousness, memory, behavior, personality. Everything we do, it derives from that, so not understanding that is an absolute crime. And now, with these probes that we are developing, we can start to record every single neuron.
NARRATOR: To map anything more sophisticated than a fly, though, Vincent is missing one key ingredient, those red fluorescent proteins. Fly brains are tiny and relatively transparent. Green fluorescent protein can penetrate them easily. But for bigger, more complex brains, scientists still need infrared.
VINCENT PIERIBONE: Again, the goal of the far red is to have this ability to shine far red light, which penetrates through tissue better. So red is just really what everybody wants.
NARRATOR: It'll take years to fish through the hundreds of samples recovered in the Solomons. They're still working to purify the bright red coral that had them so excited on the ship. But one of the fish they picked up, a species of lizardfish, seems to fluoresce far red light quite well. The team has just determined that a single protein is responsible for the red fluorescence, and Vincent hopes to soon engineer it to light up neurons.
VINCENT PIERIBONE: These tools that we are developing and other labs are developing are giving us a chance to witness those things that we have wanted to witness since neuroscience began 100 years ago, but we're, for the first time, being able to see the process as it happens.
NARRATOR: And the promise of glowing creatures isn't limited to the brain. Around the world, other researchers are harnessing them in many different ways. In Florida, Edie Widder is using bioluminescent bacteria to shine a light on pollution. Toxins in polluted water happen to interfere with the bacteria's ability to produce light.
EDIE WIDDER: The more polluted it is, the more the light dims, so you get a relative measure of toxicity.
NARRATOR: By taking sediment samples in threatened estuaries, mixing it with the bioluminescent bacteria and measuring the light they give off, the technique provides a quick and cost-effective way to detect pollution.
Elsewhere, scientists have modified firefly genes in the hopes of creating bioluminescent trees that could one day light up cities. Another lab has co-opted marine bacteria to produce an electricity-free lamp.
And it might not be a cure for cancer or a map of the brain, but one company has made biofluorescence available to the masses, with green fluorescent ice cream, a mere $220, or so, per scoop.
As for Vincent, David and John, they're already planning a return trip to the South Pacific and other remote stretches of our planet to search for new dazzling critters, both bioluminescent and biofluorescent.
DAVID GRUBER: We humans can't create these from scratch. We need to go to the corals, we need to go to these fishes, to find these molecules that we can then illuminate the inner workings of ourself. To me, I think that's just, you know, incredibly cool.
NARRATOR: We're only just beginning to see the light of this mysterious hidden world. Who knows what illuminating wonders await? But, thanks to those alluring creatures of light, the future of at least one species, our own, may be an enlightened one.
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This program was produced by WGBH, which is solely responsible for its content.
Original funding for this program was provided by Cancer Treatment Centers of America, Google, the David H. Koch Fund for Science, the Corporation for Public Broadcasting and Public Television Stations.
IMAGE: Image credit (seahorse) © David Gruber
- Marc Branham, David Gruber, Vincent Pieribone, John Sparks, Edie Widder