Bioluminescence is emission of light by a living organism. This light is not refracted light but light produced. Thousands of animal species emit light, bacteria, fungi, algae, insects, molluscs, crustaceans, and especially the deep-sea fish, who live in the abyss.
Into the abyss, bioluminescence is common with 95% of individuals collected at 4000 m depth, are luminous.
Bioluminescence is an integral part of the means of survival of these species. These animals trigger chemical reactions in which energy is converted into light energy. The bioluminescence produced a cold light, less than 20% of the light generates heat. This phenomenon is similar to the chemiluminescence but reaction is produced by a living organism. Bioluminescence is produced by oxidation of a molecule called luciferin in the presence of an enzyme catalyst, luciferase. Bioluminescence differs animals, some will emit light yellow or red or blue. It is especially in the marine world we find a wide variety of animals light. In the depths, where sunlight does not reach at least 80% of species are bioluminescent.
Bioluminescence plays various roles: communicate with congeners, mislead or frighten predators, camouflage, etc.
But we are far from having understood the subtlety of these roles. Very specific conditions prevailing at great depths led to the development of a fauna quite different from that encountered in surface. Beyond 100 m in the dark cold water, plants disappear, life in the deep sea is pure animal. The darkness of the abyss explains the large number of species blind or, conversely, species with very large eyes, often enlarged and globular allowing them to capture any light flux.
Some have bodies capable of emitting light, the photophores. The phenomena of bioluminescence are particularly developed in fish and cephalopods depth. Fish bear decoys on the slopes, on the head or at the end of appendages used lamps.
NB: The man also emits bioluminescent light source, but the amount so small that it is perceptible only by extremely sensitive cameras.