Linda Crampton has an honors degree in biology. She has taught high school biology, chemistry, and physics as well as middle school science.
What Is Bioluminescence?
Bioluminescence is a process in which living organisms produce light. The light often looks beautiful to humans and has an important function for its producer. Organisms use light for communication, for defense, or for attracting a mate or prey.
A wide variety of creatures produce light. These creatures include some types of animals, dinoflagellates, mushrooms, and bacteria. Most bioluminescent organisms live in the deep ocean, but some live in shallow water or on land.
Bioluminescence creates a cold light that is accompanied by very little heat. The process used to produce the light is complex and not completely understood. Researchers have suggested that some bioluminescent organisms might one day be useful to humans.
In this article, I describe light production in nine organisms (or types of organisms), which are listed below. I also include some additional facts about each organism or group.
- flashlight fish
- deep sea anglerfish
- firefly squid
- vampire squid
- Noctiluca scintillans (a dinoflagellate)
- Comb jellies or ctenophores
- fireflies (including Aspisoma sp.)
- Lampyris noctiluca (a glow worm)
- mushrooms of the bitter oyster fungus
Heterocarpus ensifer is a shrimp that lives in the deep ocean. Many aspects of its biology are poorly understood, including the role of its bioluminescence.
How Is Bioluminescence Produced?
Bioluminescent organisms–or at least the ones that have been discovered–contain a pigment molecule with the general name of luciferin. Different varieties of luciferin exist. A chemical reaction between luciferin and oxygen releases energy in the form of light. In most bioluminescent organisms, an enzyme called luciferase triggers the reaction. The word luciferin comes from the Latin word lucifer, which means “light bearer”.
The different kinds of luciferin have a different chemical structure. Examples of the substance include firefly luciferin, the dinoflagellate version, and the bacterial one. Vargulin is a type of luciferin found in the midshipman fish, which lives in deep water. Coelenterazine is the type found in some fish and invertebrates.
Some bioluminescent organisms make their own luciferin. Others obtain it from the creatures that they eat. Some light emitters house bioluminescent bacteria within their body and use the light produced by the microbes. Most produce the light without the aid of bacteria, however.
Many bioluminescent organisms are found in deep, dark ocean water far from sunlight. Scientists think that about ninety percent of animals in deep water are bioluminescent. Deep-water organisms usually produce light with a blue-green colour, which is the colour that travels best under water. The eyes of underwater animals appear to detect blue light better than light of other colours.
The light released by bioluminescence generally appears white, yellow, green or—especially in the deep ocean—a beautiful shade of blue.
The flashlight fish is one ocean inhabitant that produces light. The light-producing organ of the fish is called a photophore and is located beneath each of its eyes. The light is actually produced by bioluminescent bacteria that live in the photophores. The fish can flash its light on and off by covering the organ with a flap of skin that acts somewhat like an eyelid.
Though the term "flashlight fish" is often used in the singular, multiple fish with this name or a very similar one are found the family Anomalopidae. The fish are mostly nocturnal. Several theories attempt to explain the purpose of their light production. The fish might produce light for communication with other members of their species, for confusing predators, or for producing enough light for prey visibility.
The video below shows Photoblepharon palpebratus (or Photoblepharon palpebratum) when illuminated by a video light and then when the video light is turned off. The animal lives by coral reefs and is usually seen close to the ocean floor.
The Deep Sea Anglerfish
The female deep sea anglerfish or black sea devil (Melanocetus johnsonii) has a bioluminescent lure attached to a movable spine extending from her head. She also has a set of fearsome teeth. As in the flashlight fish, her bioluminescence is produced by bacteria.
When the anglerfish needs to eat, she lowers her “fishing rod” towards her mouth and flicks the glowing end to attract prey. The rest of the fish is hard to see in the darkness. Once the prey approaches, the anglerfish grabs hold of it with strong jaws. Since the stomach of the anglerfish can expand dramatically, the fish is able to eat large prey animals when they are available.
The male anglerfish is much smaller than the female and is not bioluminescent. The species has bizarre reproductive behaviour. The male attaches himself to the female’s body and supplies her eggs with sperm. The attachment becomes permanent, and the male becomes a parasite on the female. Most of his organs (but not his reproductive ones) shrivel, and he relies on the female’s body for nourishment.
Bioluminescence in the Firefly Squid
The firefly squid (Watasenia scintillans) is a tiny creature with a big light display. It reaches a length of only three inches. Photophores are present in many parts of its body and produce a rich blue light. The photophores may all emit light at the same time or the light may be released non-synchronously in a pattern. The complex light patterns are believed to have several functions. They may be a signal to rivals and mates and may confuse predators.
One of the best places to see the firefly squid is at Toyama Bay in Japan. During the mating season, thousands of squid are present in the bay. They spend the night in deep water and the day at shallow depths. While they are in shallow water, they emit their light as they search for a mate. The overall effect of thousands of squid producing blue light is said to be spectacular.
Light Production by the Vampire Squid
The vampire squid (Vampyroteuthis infernalis) doesn't suck blood as its name might suggest. The name comes from the webbing between the squid's arms and perhaps from the animal's reddish colour. The webbing produces a structure that is reminiscent of Dracula's hood. The squid is six to twelve inches long and has large and blue eyes. It also has side fins. Despite its name, it's classified in a different order from true squids.
Like the firefly squid, the vampire squid has many photophores on its body and is able to create complex patterns of flashing lights. The animal also releases a sticky, bioluminescent mucus to confuse predators. The mucus is released by the tip of the tentacles as a glowing cloud. The cloud gives the squid a chance to escape.
Researchers have discovered that the diet of vampire squids consists of marine snow. The "snow" is the collection of dead plankton, fecal pellets, and gelatinous material that sinks from shallower into deeper water. A squid catches the snow with two filaments that it extends from its body.
Bioluminescence in Dinoflagellates
Dinoflagellates belong to a group of relatively simple organisms known as protists. Noctiluca scintillans, also known as sea sparkle, is a bioluminescent dinoflagellate. It lives near the ocean surface and feeds on plankton (tiny organisms that drift in the ocean). Its body consists of just one cell, but the cell is large compared to the bodies of other unicellular organisms.
The cells of Noctiluca scintillans create a blue bioluminescence. The light is produced when the dinoflagellates are mechanically stimulated, such as by the actions of nearby predators. One theory is that the ability to produce the light developed because it distracted the predators. The light is produced by the luciferin/luciferase system.
A cell of N. scintillans is roughly spherical and looks as though it has been inflated. The cell often has a photosynthetic organism (Pedinomonas noctilucae) living inside it and has a green colour. It obtains some of its food from this organism but also obtains some nourishment by itself. Populations of N. scintillans without the symbiont and with a red colour have been discovered.
There are only almost no bioluminescent organisms in fresh water. So far only some insect larvae and one kind of limpet have been found to release light in that habitat.
Comb Jellies or Ctenophores
Comb jellies are gelatinous invertebrates that are known for the eight rows of comb-like structures on their body. The combs enable the animals to swim. Each one consists of fused cilia, enabling the comb to act as a paddle. Cilia are hair-like structures. The paddles move in synchronization, propelling the animal through the water. They sometimes create a lovely rainbow effect as light strikes them. The effect is due to the scattering of light, not bioluminescence. Some comb jellies are able to produce light by bioluminescence, however.
Comb jellies are predators. They are often small animals, but some species are several feet long. The species in the first photo in this article is Bathocyroe fosteri, which reaches a length of around 4 cm. Some comb jellies have two tentacles, which may be branched, as shown in the photo below. The tentacles contain cells called colloblasts. These produce a sticky substance that is used to catch prey. Comb jellies without tentacles use special cilia to force a current of water containing tiny organisms into their mouth.
Bioluminescent ctenophores contain complexes known as photoproteins. A photoprotein consists of luciferin in association with the enzyme luciferase. (Enzymes are a type of protein.) When calcium is available, bioluminescence is produced by the complex. If no calcium is available, light is not produced.
Fireflies or Lightning Bugs
Probably the best known example of land organisms that exhibit bioluminescence is the firefly, also called a lightning bug. Despite their name, fireflies are actually nocturnal beetles, not flies. About 2,000 different species exist. Their light-producing organs are located at the end of their bodies on the bottom of their abdomens.
Fireflies generally release their light in a series of flashes. The flashes help fireflies find mates. They may also protect the insect by warning potential predators that the fireflies taste bad. In addition, scientists have discovered that the flashes may be used to attract prey. Some female fireflies can imitate the light flash pattern of the female of another firefly species. The male of the other species is attracted by the mating signal and is eaten by the attracting female.
First firefly photo: Aspisoma sp., by gailhampshire, CC BY 2.0, via Wikimedia.org
Second and third photo: The undersurface of a New Brunswick firefly photographed with and without flash, by Emmanuelm, CC BY 3.0, via Wikimedia.org
How Do Fireflies Produce Light?
It’s not known for certain how the firefly is able to turn its light on and off, but it’s thought that the insect is able to control the quantity of oxygen inside the light organ. Oxygen availability may be determined by the presence of nitric oxide and mitochondria. The mitochondria produce energy for a cell by a process called cellular respiration. Oxygen is required for this process.
According to the theory, when nitric oxide is present, it inhibits the mitochondria in the light organs from using oxygen. The oxygen is therefore available for light production. When nitric oxide is absent, the mitochondria are no longer inhibited and use oxygen for cellular respiration. The oxygen is therefore unavailable for light production.
Glow Worm Facts
Glow worms also produce light by bioluminescence. They aren't worms, despite their name. The term “glow worm” refers to the bioluminescent, worm-like larvae of certain flies or beetles or to adult bioluminescent beetles that have a worm-like appearance.
In some places, the term "glow worm" is restricted to the female Lampyris noctiluca, which is a type of beetle. The female looks more like an elongated larva than an adult beetle and is unable to fly. She attracts the male, who can fly, with her light. The light is produced on the underside of the last three segments of the abdomen, as shown in the photo below. The light is emitted continuously, unlike the case in fire flies. Other stages of the insect's life cycle can also emit light, but the adult female's glow is the brightest.
Bioluminescent fungi produce a beautiful and often eerie glow that emanates from wood or a forested area. The glow is sometimes known as foxfire. The light is continually emitted—even during the day—but shows up best in the dark. One example of a fungus whose mushrooms emit light is the bitter oyster fungus, or Panellus stipticus. It's a common species that is found on multiple continents, including North America.
The body of a fungus consists of thread-like structure known as hyphae. The mass of hyphae is called a mycelium. The hyphae extend through the food source of the fungus. Fungi obtain food by secreting digestive enzymes into their food and then absorbing the products of the digestion. Some species produce an aerial mushroom, which releases spores as part of the reproduction process.
Bioluminescent fungi produce light as they digest wood. In some species, only the cap or the gills of the mushroom release light, while in other species only the stem glows. Sometimes only the mycelium that produces the mushroom is bioluminescent.
As in bioluminescent animals, the fungi produce their light by the luciferin/luciferase system. The function of the light is still a mystery. One theory is that the light attracts insects to aid in spore dispersal. Different species of fungi may glow for different reasons, however.
Other Bioluminescent Organisms
Bioluminescence plays an important role in the lives of many creatures, but no bioluminescent plant, amphibian, reptile, bird, or mammal has yet been discovered. (According to biological classification, fungi aren't plants.) There may be surprises in store for us, however.
Researchers have discovered that the hawksbill sea turtle is biofluorescent. It absorbs blue light and releases red and green light. Fluorescence is the process is which light of one colour (or wavelength) is absorbed and then immediately emitted as light of a different colour. While light production by the hawksbill sea turtle isn't an example of bioluminescence, it does suggest that there is more to learn about light emission in nature. It's a fascinating phenomenon.
- Bioluminescence and its use from The Conversation (Article written by a university researcher)
- Information about bioluminescence in the ocean from Smithsonian Ocean
- Facts about anglerfish from the Smithsonian Magazine
- Comb jelly information from Smithsonian Ocean
- Facts about Noctiluca scintillans from the University of Tasmania, Australia
- Geographical distribution of red and green Noctiluca scintillans from ResearchGate (Abstract and figures)
- Bioluminescence in fireflies from Scientific American
- Facts about glow worms and other bioluminescent creatures from the Wet Tropics Management Authority of Australia
- Fungal production of light from the Smithsonian Magazine
© 2010 Linda Crampton
Linda Crampton (author) from British Columbia, Canada on July 18, 2015:
Arun Dev from United Countries of the World on July 18, 2015:
Linda Crampton (author) from British Columbia, Canada on July 17, 2015:
Hi, adevwriting. Thank you very much for the comment and the kind request. The link would be nice if my hub is not already shown on your page. I'm happy to see that at the moment your hub is one of the related hubs on this page!
Arun Dev from United Countries of the World on July 17, 2015:
This hub is a great introduction to bioluminescence. Could I add a link to this hub on my hub about bioluminescent fungi.
Linda Crampton (author) from British Columbia, Canada on June 30, 2015:
Thank you very much, adevwriting.
adevwriting on June 30, 2015:
This is a good article!
Linda Crampton (author) from British Columbia, Canada on July 08, 2012:
Hi, Mary. It's certainly okay to link your hub to mine, and I will link mine to yours if that's okay with you!
Mary Hyatt from Florida on July 08, 2012:
Just to give you a "heads up"... My Puerto Rico vacation including the Bioluminescent Bay which was Day Two of my six day vacation will be published this next week (I hope). I still like to link this Hub into mine, OK?
Thanks again. Goodnight.
Linda Crampton (author) from British Columbia, Canada on July 06, 2012:
That must have very disappointing, Mary. What a shame that you didn't get a chance to swim with the bioluminescent organisms. At least you were able to see them!
Thank you very much for your comment.
Mary Hyatt from Florida on July 06, 2012:
We were so disappointed because the info on the tour said people were allowed to get into the water with these, but then because someone got injured doing that, they no longer allow that. So, they scooped up a bucket of water from the bay and let us see them in the water!
Linda Crampton (author) from British Columbia, Canada on July 06, 2012:
Thank you very much for the comment, the vote and the share, Mary. I'm looking forward to reading your hub about Bioluminescent Bay and linking to it - it sounds like it's going to be a very interesting hub! I'd love to visit the Bay - the idea of seeing millions of bioluminescent organisms is so exciting.
Mary Hyatt from Florida on July 06, 2012:
This is such a fasinating Hub. I am writing about a trip I took to Puerto Rico. We went on a tour to a Bioluminescent Bay where we saw millions of these in the water. I'm going to write a Hub about that. I'll be back to ask if I can link this Hub into mine. But for now, I'll vote this UP, and will share.
Linda Crampton (author) from British Columbia, Canada on June 03, 2012:
Thanks for the visit and the comment, clothespinnedlove.
clothespinnedlove from Wisconsin on June 03, 2012:
Linda Crampton (author) from British Columbia, Canada on February 01, 2011:
Thanks for your comment, Esmeowl12. I'll take a look at your hub.
Esmeowl12 on February 01, 2011:
Loved the article! Check out my hub on Synchronous Fireflies of the Smoky Mountains.
Linda Crampton (author) from British Columbia, Canada on January 02, 2011:
Thank you for the information, Rabid Puma. No, I hadn’t heard about "shrimpoluminescence", so I looked for information about the pistol shrimp and shrimpoluminescence on the Internet after I read your comment. Very interesting!!
Rabid Puma from Illinois on January 02, 2011:
Are you familiar with pistol shrimp? "Shrimpoluminescence" isn't actually bioluminescence, but you might find it interesting anyway.
Linda Crampton (author) from British Columbia, Canada on December 29, 2010:
Thank you so much, prasetio30!! Yes, nature does sometimes seem weird. Best wishes to you. I'm looking forward to reading more of your hubs.
prasetio30 from malang-indonesia on December 29, 2010:
Wow.... I can't say anything. This is new knowledge for me. I know some of them, but rest of them are really weird. This is a wonders of nature. As a biological lecturer, I thought you know everything about animals and plants. I am glad to know this from you. You open my eyes about what's going on out there. This time, I learn much from you. Thanks, Alicia. I give my vote special for you. Happy New Year!
Blessing and hugs,
Linda Crampton (author) from British Columbia, Canada on December 28, 2010:
Baileybear - Thanks for the comment. I find science fascinating too!
A.A. Zavala - Thank you! I'm glad that you found the hub interesting.
Augustine A Zavala from Texas on December 28, 2010:
Fascinating hub, thank you for sharing.
Baileybear on December 27, 2010:
How very interesting. I really enjoy science, particularly when on something fascinating. I have a few ideas of science topics I'd like to write about.
Linda Crampton (author) from British Columbia, Canada on December 21, 2010:
Thank you for your comment, NJ's Ponderings!
NJ's Ponderings from Hickville, NY on December 21, 2010:
Very informative and well-written. Thanks :)