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Acanthephyra purpurea and
Gonostoma elongatum(E. Widder)
A very common use of bioluminescence in the ocean is as camouflage. In the open ocean there are no trees or bushes to hide behind, there is only dim blue light filtering down from above and darkness below. Many animals like these (right) produce a very distinctive silhouette, easily seen by a predator swimming below.
Many animals in the ocean have bioluminescent light organs on their bellies that they use to disguise their silhouettes. Because seawater scatters light, these point patterns tend to blur at a distance and the bioluminescence exactly matches the color and intensity of the dim blue light filtering down from above, so these animals can hide, even in the open ocean. Move cursor over image (right) to see this effect.
(D. Smith)
This jellyfish produces a brilliant display that travels in waves over its surface. Click on the image to see this luminous display.
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WHY THEY MAKE LIGHT
Defense
One way bioluminescence is used to fend off attackers is with a blinding distraction. Like the ink cloud used by a squid to distract a predator, many animals in the ocean can squirt out a glowing cloud. This shrimp (left) actually vomits bioluminescence onto its attacker and then tail flips backwards into the darkness. Click on the animal top see this defense.
(D. Smith)
Why is a single-celled dinoflagellate bioluminescent? Because the flash it produces when disturbed helps to protect it from its predators. In this sequence the top panel shows a copepod feeding on dinoflagellates as a fish swims by in the darkness. But when, in the middle panel, the copepod encounters a bioluminescent dinoflagellate, the flash attracts the attention of the fish. Then in the bottom panel, the copepod stops feeding and escapes, because to remain is to risk being eaten by the fish. Click on panel to see the process in action.
(N. Beaman)
Like a cry for help, the dinoflagellate's flash is called a burglar alarm because it serves as an alarm which attracts the attention of the police (the fish) to the burglar (the copepod), thereby removing the threat to the dinoflagellate. This use of bioluminescence is actually very common and is responsible for some of the most brilliantly eye-catching displays in the oceans.
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DR. WIDDER WELCOMES YOU TO COME ALONG WITH HER AS SHE EXPLORES THE GLOWING, SPARKLING, LUMINOUS WORLD OF BIOLUMINESCENCE.
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