Animals That Glow

By Randi Lynn Mrvos


Squid (Histioteuthis heteropsis)
© 1999 Steven Haddock

Since ancient times people around the world have wondered about animals that glow. The earliest written records of such animals date back more than 2,500 years to ancient China. Aristotle, the Greek philosopher, recorded descriptions of glowing wood, but could offer no explanation for the curious phenomenon that caused the glow. Historians believe he witnessed foxfire, a phenomenon caused by glowing fungi. Christopher Columbus was similarly mystified by strange lights that glowed in the sea. Investigators today link Columbus' mysterious lights to a fireworm, which lives in the waters of the Caribbean.

Do fireflies come to mind when you think about animals that glow?
In fact, not all species of adult fireflies glow, and fireflies are not the only animals that can produce light. Many deep-sea animals, such as angler fish and firefly squid also have light producing mechanisms. In rare cases, some flies, centipedes, millipedes, snails, and earthworms glow as well.

The process by which living things produce light is called bioluminescence (BYE-oh-loo-muh-Ness-ens). The light that bioluminescent animals produce is cool, not hot like an electric light bulb. How do bioluminescent animals make light? Scientists have found that these animals produce light through a chemical reaction involving two elements-luciferin and luciferase. Different living creatures produce very different versions of these chemicals, and the colors of light they make can also vary. Bioluminescent animals that live on land make green or yellow-colored light. In the ocean, most bioluminescent dwellers produce blue-colored light. Of all colors, blue light is seen best in the blackness of the sea. Some fish, though, such as the black dragonfish, emit both blue and red light from light-making organs located under their eyes.

Scientists divide bioluminescent animals into two categories. Some bioluminescent animals, such as insects, squid, shrimp, and fish, may have light-producing cells, or special organs known as photophores, embedded in their skin. The other group of bioluminescent animals borrows the glow made by bacteria living in their bodies. These include flashlight fish and the deep sea anglerfish.

Bioluminescent Shrimp
© Peter Herring

Bioluminescence helps animals attract mates, protect against predators, and find food. Fireflies flash glowing signals to find mates, and their young use their light to tell enemies that they taste bad. The railroad-worm of Central and South America has two red headlights that glow. When it is disturbed, flash! 11 pairs of green lights light up on its sides. Bioluminescence is especially useful in the deepest parts of the ocean. Deep-sea shrimp emit clouds of glowing secretions to help them escape their enemies. The flashlight fish have large light-emitting patches under their eyes that can turn on and off to blind their prey. By producing a ring of light, jellyfish frighten their predators. Deep-sea finned octopuses lure their prey with light-producing organs that look like buttons stretching down each arm. The deep sea angler fish catches food by wiggling its glowing, worm-like lure, which has millions of light-producing bacteria living in it.

Jellyfish (Aequorea victoria)
© 1999 Steven Haddock & Trevor Rivers/MBARI

Human beings also make use of the light that bioluminescent animals produce. Cypridina, a tiny clam-like creature no larger than a tomato seed, produces a blue-glowing secretion. In World War II Japanese soldiers mixed dried Cypridina powder with water to provide dim illumination to read maps in the jungle without giving away their positions. In Central and South America fire beetles shine continuous light from two yellow spots located on their shoulders. Native women wear them in their hair for ornaments. People of Brazil use glowworms and fireflies to light huts or lantern gourds and wear them tied to their ankles for traveling in the dark. Scientists use luciferin and luciferase to help identify diseases. Bioluminescent chemicals glow when added to a patient's blood or to a urine sample that is infected with bacteria. Blood bank technologists know that when blood for transfusions has gone bad it glows in the dark.

Whether on land or in the sea, bioluminescence is beautiful and enchanting. The light emitted by bioluminescent animals can be bright or weak. It can blink on and off or stay on all of the time. Bioluminescent creatures also produce a rainbow of colors: blue, green, yellow, red, and orange. Just like the people of ancient times, we too are fascinated by these amazing animals that glow.

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References-Printed Materials

Barkan, Joanne, Creatures that Glow, New York, Doubleday, 1991, p.9. ISBN 0385419783

Silverstein, Alvin and Virginia, Nature's Living Lights: Fireflies and Other Bioluminescent Creatures, Boston, Little, Brown, and Co., 1988, pp. 5, 25. ISBN 0316791199

Simon, Hilda, Living Lanterns: Luminescence in Animals, New York, The Viking Press, 1971, pp.11, 12, 32, 35, 64, 76, 77. ISBN 0670435376

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References-Non-printed Materials

Bioscience Explained: Marine Bioluminescence by Edith A Widder
http://www.bioscience-explained.org/EN1.1/PDF/BiolumEN.pdf

The Bioluminescence Web Page
http://www.lifesci.ucsb.edu/~biolum/

The Firefly Files
http://iris.biosci.ohio-state.edu/projects/FFiles/

Great Moments in Science
http://www.abc.net.au/science/k2/moments/s587114.htm

HBOI Bioluminescence
http://www.biolum.org

International Society for Bioluminescence and Chemiluminescence
http://www2.unibo.it/isbc/Default.htm

Jellyfish
http://www.bio.davidson.edu/Courses/anphys/1999/Cody/Defense.html

Latz Laboratory of Scripps Institution of Oceanography
http://siobiolum.ucsd.edu/Dino_bl.html

That Special Glow
http://www.courier-journal.com/foryourinfo/082602/082602.html

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About the Author

Randi Mrvos is a homeschool teacher and a freelance contributor for Weeones, an educational e-magazine for children. Her publishing credits include The Christian Science Monitor, Highlights for Children Magazine, Scholastic Books, The Lesson Plans Page, and Parents and Children Together Online Magazine. She lives in Lexington, KY with her husband, Jim and eight-year old daughter, Abby.

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Acknowledgements

The author would like to thank Dr. Peter Herring and Dr. Steven Haddock for their valuable feedback and expertise in preparing this article.

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Photo Credits

Steven Haddock, PhD
http://lifesci.ucsb.edu/~biolum/
Defense (Aequorea victoria)
Squid (Histioteuthis heteropsis)

Peter Herring, PhD
http://www.bbc.co.uk/nature/programmes/tv/abysslive/specialists/peter_herring.shtml
Dragonfish (Pachystomias microdon)
Bioluminescent Shrimp