Bioluminescence is defined as light emitted by a living organism. A form of chemiluminesscence, bioluminescence is a chemical reaction that occurs within the organism to produce light. The substrate, called a luciferin, is either taken in via diet or, in some cases, is synthesized internally by the organism.
The result is an eerie, otherworldly glow, often blue or green in color. The occurrence of bioluminescence is widespread, with most of its wielders living in the ocean, and its purposes variable.
A relatively newly described species of deep-sea worms called “green bombers” throw packets of green bioluminescent light when under attack to distract their predators.
A species of mushroom, described in BBC’s Planet Earth II Jungles Episode, is believed to use bioluminescence to attract bioluminescent beetles which pick up and disperse their spores.
Species of squid use bioluminescence to counter-illuminate, a way to camouflage one’s silhouette by matching the light emitted from the body to the light of the surroundings. This allows the species to avoid detection by becoming essential invisible from below.
Its incredible what the natural world has developed and evolved. And there is still so much to be discovered!
For more on bioluminescence, there is a great TEDed video.
National Geographic has a set of beautiful photographs of bioluminescence.
To see bioluminescence in action, check out this video of a man surfing a Red Tide.