Bioluminescence. Copyright 2012 LessonSnips

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1 Bioluminescence Bioluminescence is a fascinating capability of some creatures to create their own light from within the body. Bio is the root of biology and biography and refers to life; luminescence means emitting light without heat. Together they imply creating light from a living organism. Fireflies and glowworms are the most familiar creatures that can produce light. Researchers have studied fireflies extensively in an attempt to figure out how they emit light. If the researchers could duplicate the firefly s light emitting process it could potentially be a useful way to generate light without using electricity. There are only a few land-based creatures that have bioluminescent properties. Besides fireflies and glowworms, some species of fungi, centipedes, beetles and snails emit light. Yet bioluminescence is a property that is common to the inhabitants of the ocean, especially those that live in the ocean depths. Sunlight penetrates approximately 4,000 feet below the surface of the ocean, getting dimmer with each foot lower from the surface. After the sunlight finally fades at about 4,000 feet, the undersea world is completely dark except for the millions of tiny lights that are generated by bioluminescent creatures. In the deep ocean, about 80 to 90 percent of the inhabitants emit light. The natural world is a place filled with predators. Carnivorous creatures are predators that eat other creatures. Imagine the deep ocean where the water depth can reach seven miles from the surface. Some form of life exists at every level of the ocean column, an imaginary cylinder that runs from the surface to the ocean floor. Within the ocean column, where can creatures hide from predators? Many ocean creatures have adapted to living in the darkness as a means to hide from predators. Bioluminescence provides predators with a mechanism for finding food and for prey animals to defend themselves and locate each other for mating. Bioluminescence in Predators Predatory ocean creatures like species of shrimp, squid and fishes use their headlights to emit light in order to find prey. Headlights are found on the front of the animal, usually in the vicinity of its eyes. For many species these headlights have a reflective surface so that the light penetrates outward and these headlights

2 can be closed when they are not needed. Light traveling within the water of the ocean has different properties than light that travels through air. The wavelength corresponding to the color blue travels the furthest in ocean water so many species that have headlights that emit blue light. The flashlight fish emits a greenish light from patches under its eyes. Instead of generating light itself, the flashlight fish has a symbiotic relationship with a species of bacteria that inhabit the patch. These bacteria are responsible for producing the fish s light. Other predators use bioluminescence to attract prey. Some species of fish feed on the organic material that is settling towards the ocean floor. This organic material is produced by species living higher in the ocean column. During its journey to the depths this organic matter is also food for bioluminescent bacteria that attach themselves to the particles. Fish that feed on this matter are attracted to the light from these bacteria. There are predator species that have a bioluminescent lure as a body part. This lure operates like a fishing line and is usually located at the top of the predator s head or on its chin. Some species, like the 160 known species of anglerfish that inhabit the deep ocean, dangle a lure from the tip of a long tail. The lure resembles the glowing bacteria inhabiting organic particles. The lure attracts fish species that feed on the particles which then get attracted to the lure and become food for the predator. Bioluminescence as Defense Many ocean prey species have photophores which are organs that produce light. The positions and pattern of these photophores varies with the species. The positioning and use of photophores depends upon the camouflage needs of the creature. For example, some predator species seek prey above them in the ocean column. These prey species, like northern krill and hatchetfish, have photophores located on their underside in order to blend their silhouettes into the sunlight as the predator looks upward. This defense technique is called counterillumination. What happens on a cloudy day? The prey species can dim their photophores to match the light penetrating the ocean water. Some prey species have a defense mechanism similar to the octopus. Instead of spraying a murky ink in the water like the octopus, these creatures send

3 out bioluminescent chemicals that blind or otherwise interrupt the predator, allowing the prey to escape. A third form of defense mechanism is called the burglar alarm. In the presence of a predator some prey species will emit very bright light with the hope that this flash of bright light might attract a larger predator that will attack or at least frighten the original predator. The deep-sea jellyfish is an example of a marine creature that uses this burglar alarm technique of defense.

4 Circle True or False after analyzing each of the following statements. 1. True False Fireflies and earthworms are the most familiar land-based creatures that are bioluminescent. 2. True False Sunlight penetrates a maximum of approximately 1,000 feet below the surface of the ocean, getting dimmer with each foot lower from the surface. 3. True False In the deep ocean, about 80 to 90 percent of the inhabitants are bioluminescent. 4. True False The ocean column is an imaginary cone that runs from the surface to the ocean floor. 5. True False Bioluminescence provides predators with a mechanism for finding food and for prey animals to defend themselves and locate each other for mating. 6. True False The wavelength corresponding to the color red travels the furthest in ocean water so many species that have headlights that emit red light. 7. True False The flashlight fish has a symbiotic relationship with a species of bacteria that are responsible for producing the fish s light. 8. True False Anglerfish that inhabit the deep ocean dangle a bioluminescent lure from the tip of their chin. 9. True False Counterillumination is a defense technique for prey species that live in the sunlit areas of the ocean. 10. True False Many ocean prey species have photophores which are organs that produce light.

5 Answers 1. False 2. False 3. True 4. False 5. True 6. False 7. True 8. False 9. True 10. True