Dinoflagellate luminescence
Dinoflagellates are giving off blue
light in this image of bioluminescence
Image from Wikimedia Commons

Have you ever wondered how fireflies produce and emit the small light on their bodies? The light, which is also called bioluminescence, is the result of a chemical reaction inside their bodies. Bioluminescence is the production and emission of light by living organisms. It is the result of a combination of two chemicals called luciferin and luciferase. Sometimes other substances are required such as adenosine triphosphate or oxygen. Luciferin is the light-producing substance, and luciferase is an enzyme that sets off the reaction. The chemical reaction begins when luciferase acts as a catalyst and lets oxygen combine with luciferin. The products are photons of light and oxidized luciferin, which becomes inactive. Both luciferin and luciferase are general terms. There are actually many different types of substances that can act as the luciferin or luciferase and differs depending on the species of the organism. Coelenterazine is a common luciferin in marine animals.

Bioluminescence is most often seen in marine organisms. It only occurs in a few species of fungi and insects on land, and it does not happen in freshwater. A well known example of bioluminescence is the firefly. Other organisms are the deep sea anglerfish, the squid, the lanternfish, and the gulper eel.

Most organisms in the sea emit light between 440 nanometers and 479 nanometers, which is a blue color. Blue-green light spreads the farthest in water. Many organisms are only able to see blue light because they don’t have the pigments needed to see other colors. An exception is the malacosteid fish family, which can produce and see red light. This is a useful advantage because the fish can use their red light to see and find prey, but their prey won’t be able to see them or their red light.

There are many uses for bioluminescence. Fireflies flash the light at each other to communicate. Deep sea fish use the light they emit like a flashlight to spot prey. Other fish like the deep sea anglerfish use the light to attract their prey. Some animals release a cloud of bioluminescent fluid to defend themselves like how octopuses eject dark ink, or they blind their enemies with their bright light. In the deeper parts of the ocean where there’s no light, it is difficult to see things below you, but you can sometimes see the shadow of something above you. Some animal species have spots of light on their undersides that lets them camouflage into the light from above. This is called counter-illumination. Some squid can emit green light in warm water and blue light in cold water. This is because deep in the ocean where temperatures are colder, the sunlight has been filtered and only blue light remains. The squid emit blue light from their underside to blend in. Then at night the squid migrate up to shallower waters, where there is both blue and green light, so the squid emit both green and blue light to blend in.

Bioluminescence ties in with some of the topics that we have covered in class. In chapter one, we learned about the ten themes of life. Bioluminescence ties in with the theme of adaptation because many deep sea organisms have adapted to the lack of light by creating their own light and using the light to attract prey or fight off predators. Bioluminescence also ties in with the unit about proteins and enzymes, since bioluminescence is the product of a chemical reaction involving luciferase, which is an enzyme, and luciferin, which can be a protein. It is amazing how organisms have adapted to be able to create their own light. We would save a lot of money if humans could produce their own light.

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