The word bioluminescence is hybrid and comes from Latin and Greek. Bios , from the Greek, means life, while lumen , from the Latin, means light. In practice, bioluminescence refers to the production and emission of light by a living organism, being a natural occurrence of chemiluminescence.
Less than 20% of light generates thermal radiation, but it is important to remember that bioluminescence is different from fluorescence, phosphorescence or light refraction. It is believed that, according to studies, 90% of the abyssal life somehow produces bioluminescence, with the majority of the light emission of these beings being of blue or green spectrum, which are more easily transmitted by sea water. Some species of animals, however, emit red and infrared lights, or even those of the genus Tomopteris, yellow.
The living beings
Chemiluminescence is when the energy resulting from a chemical reaction is released as an emission of light made by many living beings. As an example of animals, we can mention fireflies, also known as fireflies, which produce luciferin, which is a pigment that reacts with oxygen and creates light, in addition to luciferase, which is an enzyme that acts as a catalyst, that is, an accelerator of the reaction. This reaction, however, is sometimes mediated by some cofactors such as calcium ions or ATP, and can happen both inside and outside cells.
There are several groups that have the process of bioluminescence, involving vertebrate animals and marine invertebrates, or even on terrestrial organisms. Marine bioluminescence, however, is the most easily found, being rare in terrestrial animals. Some larvae, insects, annelids, fungi and arachnids have this capacity, and the most well-known terrestrial form is the firefly.
This bioluminescence, however, despite being beautiful, is not just for beauty, but has some functions. In some cases, it is used for backlight, adjusting the intensity of the bioluminescence to match the intensity of the upper ambient light, making it partially camouflaged.
Another function is mimicry, to attract prey. Some fish such as Melanocetus johnsonni , for example, have a pendant appendage that extends from the head forward, attracting small animals at an easier distance to attack. Another interesting case is the shark Isistius brasiliensis , which uses this technique in a different way. In addition to attracting prey, it camouflages itself, appearing to be much smaller than it really is and attracting predatory fish. When they come to feed on what they think is a small animal, they end up being attacked by the shark.
In addition, they can attract partners, such as fireflies, distraction, such as squid and small crustaceans, repulsion as firefly larvae, and communication, as in some bacteria. Finally, the reason that may be, for some, the most obvious: lighting. Some fish use this lighting to easily see prey that is usually invisible in deep ocean environments.