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Bioluminescence: Light Emission and Function in Eight Organisms

Linda Crampton has an honors degree in biology. She has taught high school biology, chemistry, and science 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, fungi, protists, 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 eight types of organisms, which are listed below. The use of bioluminescence in these organisms and in others is fascinating.

  1. flashlight fish
  2. deep sea anglerfish
  3. firefly squid
  4. vampire squid
  5. Noctiluca scintillans (a dinoflagellate)
  6. fireflies (including Aspisoma sp.)
  7. Lampyris noctiluca (a glow worm)
  8. mushrooms of the bitter oyster fungus

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. 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.

There are several kinds of luciferin, each having a different chemical structure. Examples 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.

The Flashlight Fish

Many bioluminescent organisms are found in deep, dark ocean water far from sunlight. In fact, scientists think that about ninety percent of animals in deep water are bioluminescent. Marine organisms usually produce light with a blue-green color, which is the color that travels best under water. The eyes of underwater animals detect blue light better than light of other colors.

The flashlight fish is one deep water 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, fish with this name are found in several families. Several theories attempt to explain the purpose of the 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 when illuminated by a video light and then when the video light is turned off.

The Deep Sea Anglerfish

The deep sea anglerfish or black sea devil (Melanocetus johnsonii) has a bioluminescent lure attached to a movable spine extending from its head. It also has a set of fearsome teeth. As in the flashlight fish, the bioluminescence is produced by bacteria.

When the anglerfish needs to eat, it lowers its “fishing rod” towards its 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 firefly squid, sparkling enope squid, or hotaru-ika has numerous photophores. It's admired for its bioluminescence and is also used as food.

The firefly squid, sparkling enope squid, or hotaru-ika has numerous photophores. It's admired for its bioluminescence and is also used as food.

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 a 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 as a glowing cloud that gives the squid a chance to escape.

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.

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.

Bioluminescence produced by a large population of dinoflagellates is often beautiful.

Bioluminescence produced by a large population of dinoflagellates is often beautiful.

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.

bioluminescence-in-the-living-world

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 Worms

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

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.

Fungi obtain food by secreting digestive enzymes into their food source and then absorbing the products of the digestion. 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 most 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.

The bitter oyster fungus is bioluminescent.

The bitter oyster fungus is bioluminescent.

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 recently 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.

References

© 2010 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on July 18, 2015:

You're welcome!

Arun Dev from United Countries of the World on July 18, 2015:

Thank you!

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.

Thanks!

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!

My best.

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:

Great article!~

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 :)