Bio-luminescence for creatives, the magical world of organic light.

What is bio-luminescence

Bio-luminescence is, simply said, a chemical reaction that causes light. Most of the time, when a chemical reaction occurs, it causes heat. But in the case of bio-luminescence, it only causes light. Technically though, at least in animals, the reaction is caused by the oxygen oxidation of an organic molecule called the ‘luciferin’. This luciferin molecule is then catalyzed by an enzyme that’s called ‘luciferase’. Together, this causes a bright flash of light or a glow. This glow you see is coming from active photons, or units of light. Sometimes there are more molecules involved than those mentioned before.
It is thought that the light intensity is the direct result of the actual velocity (speed) of the enzyme-substrate reaction. The higher the velocity, the brighter the light.

Fun fact:
Did you know that Luceferin comes from the word Lucifer? It means Light Bearer.

Distribution of light on a single organism

The distribution of light on different species is really varied. Many creatures, like fish and squids, have organs called photophores. These are organs that emit localized light on specific areas of the body. These photophores can be controlled by the animals, which decides when they will light up and when not. Other creatures don’t have these organs, they glow consistently on specific body parts, or glow from top to bottom (some bacteria and mushrooms).
Some animals can spit out a glowing substance, like some squid species and a tiny crustacean called ‘ostracods’. Both animals will produce a light bomb to illuminate their predator and scare them off.
There are even animals out there that have glowing organs. This you can only see when you open one up. It’s likely the result of their diet, or storage of the needed molecules to create light on other places of the body.

Fun fact:
Did you know that bio-luminescence evolved over 50 times and is now produced by over 1000 different species?

Bio-luminescence is mostly seen in the ocean. This makes sense, as all life came from the ocean. Bio-luminescence, therefore, had more time to creep into many species. But the darkness, especially in depths beyond 200 meters (650+ ft) makes bio-luminescence a key to life. There are many animal species out there we likely didn’t discover yet. But bio-luminescence is way more abundant among marine life than in terrestrial life.

Different manifestations of bio-luminescence

Bio-luminescence can manifest in many different ways and patterns. These patterns give off different signals, and just like the goal of bio-luminescence, has different meanings.

• Flashes (Mating signal for fireflies, and defense for Ostracods and squid).
• Dot pattern outside the body (Mating signal of Ostracods. Male Ostracods let females know where they’re going).
• Chemical bombs (Ostracods and squid as a defense mechanism).
• Permanent glow (To attract prey or reproduce, like click beetles or mushrooms).
• Circular glowing patterns (Seen in Atolla jellies, likely to attract prey or as a defense mechanism).
• Rippling light-waves (Seen in some comb jellies).
• Blizzards (Seen in some brittlestar starfish, when they are disturbed).

Click here to find out how bio-luminescence looks. (Clicking the link will scroll you down to a video).

Where to find bio-luminescent light

Bio-luminescence is a wonderful tool in the creative world. It’s a challenge to use for more advanced artists and an interesting feature in storytelling. But as with any remarkable feature, it’s useful to understand how it works, and where it comes from. Of course, you can use it on anything, and anywhere, but understanding its nature will help you to apply it in a believable and natural way.

So, where can you find bio-luminescent light? Well… Everywhere, really. You can find it in animals and a wide variety of fungi. However, you won’t see it in the plant-world, unless you’re looking at engineered plants. Another exclusion is mammals. We mammalian beings can’t emit light on our own unless we’re yes. You guessed it already: Are engineered.

What is the function of bio-luminescent light?

The short answer is to survive and reproduce. The longer answer is more complex and is best understood in the depths of the ocean beyond 200 meters, where no light from the surface can reach. Here we see that it can have many different functions, like:

• Defense (scaring off, or confusing predators).
• Schooling (fish can find each other and group together, also a way of defense).
• Lure (Light is the only thing visible in depths, with a luminescent lure you can be pretty sure to lure your prey your way).
• Feeding (Not only to lure your prey but also to find food on the ocean bottom).
• Communication (In the dark, the only really effective way to communicate is with light).
• Mating (Cause how else will you find your mate?)
• Camouflage (When schooling together, light is a perfectly confusing camouflage!)

Fun fact:
Did you know that there are bio-luminescent lollypops? They start glowing when they get warm and wet. Bio-luminescence is completely harmless.

Bio-luminescent color spectrum’s

Bio-luminescence is caused by a chemical reaction, causing a light that falls within the color spectrum we people can see. Which is roughly 400 to 700nm (wavelength) This wavelength starts at zero and is infinite, Before 400 we find ultraviolet light, X-rays, and Y-rays, while beyond 700 we find infrared, microwave, short radio waves, FM and AM, and long radio waves. Bio-luminescent light covers nearly all of our visual spectrum with exception of a few tints within the magenta range.
Terrestrial life usually emits light between 460-635nm while marine life emits light around 450-490nm, but there are exceptions to that rule. Comb Jellies for example do also emit orange-red light. This preferred color spectrum likely has to do with the fact that marine life is better suited to see blues, greens, and purples, as those are the wavelengths that can penetrate water, especially in deeper areas. Terrestrial life is better suited to see yellows. Blues and purples are less likely to be found above sea level.

Different organisms that emit bio-luminescence

Many organisms emit bio-luminescent light. From marine life to terrestrial life, and from tiny bacteria to large squid and jellyfish. But also mushrooms, which likely grow in your backyard. Key is though where and when to find them, and under which circumstances. We are still discovering new organisms that emit light, some of which are very faint and can hardly be seen on a starry night.

Fireflies

When you think of bio-luminescence, the first thing that comes to mind is probably fireflies. They’re fairly common and can be found throughout the globe. But did you know there are roughly 2000 different firefly species? It’s not uncommon to find up to 15 different species in the same area.
The light display comes mainly from the males. Every species has its own flight pattern. Some will flash their light when they fly up, while others do that when they fly horizontally. They have different flash patterns too, and some species create the so-called Christmas tree effect. Their flashes are tuned with that of their neighbors until they all flash at the same time. They usually do this while they’re in tree canopies.
The same species can also have its own ‘dialect’ in different areas. Females tend to respond with a single flash when they approve of a male nearby.

Some firefly species can’t create light of their own. Instead, mainly the females, mimic the light flashes to attract males from a different kind of firefly. When a male approaches her, she grabs him and munches down on his body. That way she can obtain everything she needs to emit her own light.

Click-beetles

Click-beetles can be found throughout the world. One of the places you can find their larva is in termite mounds, where they permanently hide out in their little tunnels until they grow into a beetle. When night falls, the click beetle starts to emit a faint greenish-light. Any curious insect that comes to have a look at that light is snagged by the larva, which just sits and waits with its jaws wide open. The larva emits light mainly from its head, but some also have a dotted pattern running down its body. When they’re disturbed by a potential predator they start glowing even more.
Adult click-beetles also emit light, and so do their eggs which are deposited on, or in suitable soil.

Glowworms

In many temperate and tropical regions, glowworms can be found all around the world. ‘Glowworm’ is a collective name for different groups of insect larva. This means they’re not really worms, although they look that way.
Glowworms are best known from the glowworm caves. The larva lives in large groups on the ceilings of the cave, creating strands of mucus with sticky droplets attached. When darkness falls, their shiny hinds become very visible, attracting insects which then will get entangled in the strands of sticky mucus, providing a nice meal. These particular glowworms are the larva of the fungus gnat, not really your most fancy bug out there. These caves however are a really famous tourist attraction. Waitomo Glowworm Caves in New Zealand are among the highest-rated glowworm caves.
These species can be found in North America, Europe, Australia, and Asia.

Fish

Many fish glow, especially beyond depths of 200 meters. A good example is the angler-fish, which has a glowing protrusion on its head which it can wave around like a flag. She does this right in front of her enormous jaw. It acts as a lure, attracting prey animals, and is proving to be a great tool for that purpose, but also to attract a mate. Only female angler-fish have a glowing lure. It holds glowing bacteria, making this phenomenon a perfect example of a symbiotic relationship between two different species.

Fun fact:
Did you know the male angler fish is usually not much larger than the female angler-fish’s tail fin? It’s so rare to find a mate that the male angler-fish will attach to the female for life. They fuse together and from that point on he will be no more than a sperm-providing attachment that lives off of the nutrients in the blood of the female. No, he doesn’t feed on her, instead, their blood vessels merge together and become one as well.

Another remarkable fish that lives in symbiosis with bio-luminescent bacteria is the flashlight fish. This fish has special ‘containers’ under its eyes, illuminating the eye and the ocean floor constantly. These fish live in schools and whenever they turn into another direction, they briefly ‘blink’ their lights.

There are many more fish out there that are bio-luminescent, too many to cover. But some other remarkable species are:

• Dragonfish (blue)
• Lanternfish (several different species, emitting green, yellow, or blue light)
• Chain catshark (yellow/green)
• False stonefish (red)
• Urobatis ray (yellow/green)
• Chlopsid eel (yellow)
• Eviota Goby (red)
• Acanthurid (yellow/green)
• Dorsal Flatfish (orange/green)
• Lizardfish (yellow/green)

Dino-flagellates

Dino-flagellates, you probably didn’t hear of that word before. But you saw them before! You likely even swallowed them when your best friend tried to drown you during a friendly fight in the ocean. Thing is, they’re so small that you usually don’t see their light. However, sometimes when a plankton bloom occurs, the Dino-flagellates, one of the biggest one-celled organisms, neither plant nor animal, bloom as well. They feed on dying plankton and fish, and when disturbed they give a flash of light. Which is most likely a defense mechanism.
When they are together in large volumes, they create milky blue waves, and whenever disturbed by movement, they will glow up as well.

Their liquid light looks like magic. Swim in it and you will feel like you’re flying. Dive in it and you will feel like you are among the stars. If you ever have the chance to witness it yourself, don’t let that chance pass you by. The best place to see this natural phenomenon is in Puerto Rico’s ‘Bio-luminescent bays’. The way these bays are shaped makes the Dino-flagellates accumulate, causing a very high concentration of these bio-luminescent organisms.

Click here for a video (The link will scroll you down to the video thats at the bottom of this chapter)

Fun fact:
Did you know that, when you leave a fish (for example a sea bream) in the fridge, it will start glowing after a few days? This is because Dino-Flagellates start feeding on the decaying fish.

Squid

There are several squid out there that use bio-luminescent light. The aptly named firefly squid is one of the best known bio-luminescent squids because they leave the ocean depths to feed at night, and because, during spawning season, females gather in large numbers at the oceans surface. In the depths of the ocean they tend to use blue light to attract their prey. Though they’re also capable of using green, red and yellow light. But it’s also thought that they use their light as camouflage (counter-illumination when seen from below, matching the water and/or sky brightness above), defense, and to attract mates.
They’re so well known because of the spawning gathering of the females. After spawning they will die, but before that happens, fishermen will catch the exhausted animals. Especially in Japan they’re a seasonal delicacy.

But there are way more squid out there that are bio-luminescent. In total there are roughly 700 different species that emit light, here are some of them:

• Humboldt squid
• Hawaiian bobtail squid
• Histioteuthis
• Abralia veranyi
• Vampire squid
• Giant squid
• Moonlight mimicker

Click here for a video (The link will scroll you down to the video thats at the bottom of this chapter)

Jellyfish

Many jellyfish glow. Jellyfish are strange creatures, simply because of what they are, and how they develop into an adult. Especially those that live at great depths emit light. Just like other animals, they do this to hunt, and scare off predators. But because jellyfish are such simple lifeforms, it’s hard to tell how complex (or not) the use is of their bio-luminescent light.

The Atolla jellyfish is probably one of the biggest freaks of nature. They look fairly developed for a jellyfish. They have a solid looking ‘body’ with tentacle-segments, each segment sporting a long thin tentacle. The dome-shaped bell is translucent, and emits light. Illuminating the insides of the jellyfish with a milky blue light. If they were to fly in the sky, they could easily be taken for a UFO.

The comb jellyfish species are likely the best known jellyfish out there. It’s a fully translucent jellyfish in the shape of a comb. The primary ring canals (the vertical rings lining a jellyfish’s bell) glow in a wide variety of colors in a rolling pattern. These jellyfish don’t have nettle cells, unlike other jellyfish. They therefore are their own kind of subspecies within the Cnidaria phylum.

Roughly half of all jellyfish out there emit bio-luminescent light. Here are some examples:

• Crystal jelly
• Upside-down jelly
• Aequorea jellies
• Helmet jelly
• Hydromedusa jelly
• Colobonema jelly
• Bloodbelly comb jelly

Click here for a video (The link will scroll you down to the video thats at the bottom of this chapter)

Ostracods

Ostracods are funny beings the size of a grain of sand. They’re little crustaceans, swimming through the ocean. They deploy their bio-luminescence in many ways, and their light is one of the brightest ones. It’s a defense mechanism and a way to attract mates. They’re prey animals, but when eaten they set off a light bomb. They spit out a cloud of light, illuminating its predator, making it visible to its own predator. This also blinds the fish for a short period of time.
These fish don’t know how quickly they need to spit out the Ostracod when this happens. If they swallow the Ostracod, or the light they emit, the fish end up glowing from within for a little while. This makes them a really easy target for larger predators.

Ostracods are one of the few creatures that can leave a glow outside their bodies. They use this for finding a mating partner too. The male Ostracods leave a dotted string in the water or light. These dots are not connected to each other. They’re individual dots, following the direction the male Ostracod is swimming. Every half a second the male leaves a dot behind, so females can come from their hiding places and know exactly where the male will be a half a second later. Like some firefly species, these Ostracods tend to sync their glow pattern.
Even more than with Dino-Flagellates, you will have the feeling like you’re swimming in a galaxy at light speed when you go swim with them.

Click here for a video (The link will scroll you down to the video thats at the bottom of this chapter)

Mushrooms

Mushrooms is one of the few organisms that isn’t an animal (or part animal) that glows. Glowing wood for example, is caused by the Mycelia of the mushrooms (the stringy usually white fuzzy part of the organism). They glow under the ground too, why they do that is unknown. However, the use of glowing fruiting bodies (the actual mushrooms growing above the ground) have a logical explanation.
Even though their glow is faint, (You won’t be able to see it if you have a flashlight on, or there are streetlights nearby, or its full moon and a clear sky) they do attract insects which pick up their spores and scatter them over a wide area. Which technically makes them the flowers of the night.

Glowing mushrooms are more common than you may think. It’s not unlikely to find them in your back garden. Roughly 80 of the more than 100.000 mushroom species glow. However, they only grow in specific habitats, on specific soils and woods and usually only after rainfall in the autumn. Which makes it harder for you to spot them.

There’s more!

Yes there is! But there are just way too much animals that are bio-luminescent out there to tackle in this article. But think of corals, starfish, snails, millipedes, worms, sharks, etc. Not all subspecies within an species makes use of bio-luminescent light, but it is widely seen among many different organisms. To this day, scientists keep discovering new glowing species. Either species that haven’t been discovered before, or species that glow so faintly, or only in some areas of the world. We really do live in a magical world.

Video bio-luminescent species

• 0:00 Ostracods mating signals
• 0:58 Brittlestar starfish warning signal
• 1:05 Ostracod lightbomb illuminating and blinding a fish
• 1:09 (Firefly) squid
• 1:20 Brittlestar starfish warning signal
• 1:24 Ostracod lightbomb
• 1:30 Jellyfish
• 1:39 Dino-flagellates
• 2:13 Cuttlefish
• 2:57 Giant squid

Different kinds of luminescence

There are many kinds of luminescence, but they shouldn’t be mixed up with each other. Bio-luminescence has its own very unique traits, and so do the other kinds of luminescence. The way these lights are produced is very different too, and so are the characteristics. We quickly run through some of them, to get a grasp on what’s out there. It’s good to be aware of these differences because it will help you find the right reference material when you’re working on your designs, and tell an accurate story.

Bio-luminescence

We already know this one. It’s actually light caused by a cold chemical reaction. It’s seen in the animal- and fungi world, but not in plants, or mammals. There is a wide variety of colors, throughout nearly the whole color spectrum we people can see. It’s used by all kinds of creatures for survival- or reproduction purposes.

Fluorescence

Fluorescence is a different way of emitting light. It’s not just a bright color, like your fluorescent markers. It’s actually light that’s absorbed by the organism, and emitted right back out again. However, these organisms tend to absorb light of a short wavelength (ultra-violet, x-rays, or another form of radiant energy) and emit light of a long wavelength. Ultraviolet has the shortest wavelength. From there it moves to blues, cyans, greens, yellows, oranges, reds, and finally infra-reds, the last of which we can’t see like we can’t see ultra-violet. An organism absorbing these radiant lights can emit any color from blue to red, but not the other way around.

Creatures like corals, jellyfish, fish, parrots, butterflies, South American spotted tree frogs and the loggerhead, and hawksbill sea turtle emits fluorescent light.
For an organism to emit fluorescent light, it needs access to the light of the right wavelength as it will bounce the light right back out again in another color. When this light is not available, there will be no fluorescent light.

Fun fact
Did you know that green fluorescent proteins (GFP) are used in gene- and protein tagging? That’s a nice little feature for your futuristic story.

Phosphorescence

Phosphorescence is a little different from Fluorescence, but it’s a lot rarer in the natural world. It only seems to exist in some cnidaria (jellyfish, corals, etc). The difference between fluorescent and phosphorescent light is that the latter emits light for a longer period of time, instead of bursting it out all at once. In modern technology, we use this kind of light in watches and glowsticks. Or the glowing stars you used to stick on your ceiling when you were young. It’s likely though that many more species emit this kind of light. But because the same process is used as with fluorescence, the light that’s emitted is dispersed over a long period of time. Therefore the glow is very dim and might be overpowered by other light sources.

Iridescence

Iridescence, unlike the luminescence’s mentioned earlier, doesn’t create light. Instead, it interferes with light with the help of structural coloration, which is caused by micro-structures on the surface that interfere with light. It’s so striking because it amplifies colors and changes these colors depending on the angle you look at it. The same counts for pearlescence. However, pearlescence reflects light that’s closer to the white spectrum. Giving peals their unique appearance. We see iridescence in feathers, shells, exoskeletons, scales of both fish and snakes, butterflies, flies, plants, and many different minerals and oils. When the sun is aligned just the right way, when the temperature is right, and there are clouds in the right spot, clouds will also be iridescent.

We people love these colors, so we use them everywhere. On car paint, nail polish, smartphone (back)panels, stickers, etc. Some minerals we love to have around are Bismuth, Goethite, and Labradorite. They all have extremely vibrant iridescent colors and are very easy to come by.

Origins of bio-luminescent light

You may wonder why something remarkable as bio-luminescence came to be: Well, that’s still hard to say. It’s clear why and how animals use this skill these days, but how it saw the ‘light of day’ is still being debated. One of the likely explanations is that bio-luminescence, back in ancient times, was a by-product of the metabolism of bacteria. And as most life stems from bacteria, it’s a logical explanation that some species happened to inherit this trait, and started using it to their advantage.

Fun fact:
Did you know that in some areas the same species may be bio-luminescent, while in other area’s they’re not? This is likely because of their dietary presence. They need specific nutrients or species to be able to use bio-luminescent light.

But on land we see similar displays. Glowworms and click beetles use their light to lure in prey and fireflies and mushrooms use this light to reproduce. The first to signal between sexes, the second by attracting insects which then spread their spores.