[Animals] 5 animals that glow in the dark

[#Wittels-]

Although it is something relatively unusual, there are living beings with the ability to emit their own light; It is called bioluminescence, and it can serve as a means of communication, claim, warning, threat or bait to hunt.

 

The animals that live during the day and where the sunlight reaches without obstacles rarely notice, but among nocturnal animals, or among those that live in dark places, a phenomenon occurs with a relatively unusual frequency that never ceases to amaze us. . In biology it is called bioluminescence, the ability of some organisms to emit light with their own body.

The biochemical and physiological mechanisms responsible for the same function may be different between different groups of living beings. In most of the large groups, the genes and proteins involved in the bioluminescence process are unrelated and evolved independently. It is estimated that bioluminescence, throughout the long and extensive history of the evolution of life, may have arisen up to 30 times.

However, the most common is that the process happened thanks to the chemical oxidation reaction of a reagent, which in each group can be different, but whose family is called luciferin —from the Latin, 'that carry light'—, and through the action of an enzyme, which is called luciferase —the ending '-ase' indicates that it is an enzyme, a kind of biological catalyst—. These chemical reactions emit photons, which ultimately make up light. There are bacteria, dinoflagellates and even bioluminescent fungi. And of course, there are also several groups of animals with that ability. Of these, the best known example is that of the fireflies, whose name comes from the Latin lucerna, which means 'candlelight' or 'lamp'.

Among the fireflies, only the females, wingless —without wings— are capable of shining, and they do so through the final region of the abdomen. The winged males flutter at night looking for those tiny points of light that illuminate the forest, like stars that show sailors the way home.

But even if they are capable of emitting light, the name of 'oil lamp' does not do them justice. A lamp burns a fuel, generally an oil or other type of fat that impregnates a cotton wick, and its flame is the one that lights up in the dark, like a tiny torch. However, the chemical process that allows fireflies to glow is different.

In a lamp, light and heat is emitted by the combustion of oil, which is an oxidation reaction. Fireflies also take advantage, as has already been explained, of oxidation to fulfill their most famous function, but instead of doing it by combustion, they use their own metabolism, with very low heat emission.

fish of the deep

In the abyssal zones of the sea, in the dark abyss where the sun does not reach, there is a strange ecosystem composed mainly of animals and microorganisms that feed on everything that precipitates from the parts where there is more light, and other animals that eat these first. Much of these animals are blind, but not all. In fact, some fish use the light they emit as a form of communication, claim, threat, or as bait to attract their prey.

Some do not emit light by themselves, but instead contain organs under their skin in which they maintain colonies of luminous bacteria in symbiosis. Although many others, such as the frogfish of the genus Porichthys, do have their own light-emitting mechanism.

Among these luminous fish are the viper fish, the dragon fish, the demon fish, and many other animals with no less terrifying names, which live up to their nomenclature with their spooky appearance. Creatures that seem to appear by H. R. Giger or extracted from a novel by H. P. Lovecraft, and that could po[CENSORED]te the nightmares of those who have seen them... if it were not for their size, most fit in the palm of a hand.

Creatures of an almost alien aspect, that po[CENSORED]te a world completely different from the one we know; a world of water and darkness, with a pressure that would crush a human being; a hostile world in which any creature can become prey to a larger one. Big eyes that distinguish colors, and huge mouths, with long and irregular teeth, transparent, and sharp as needles.

Terrors hidden in the darkness, masked by the dazzling brilliance of beautiful and alluring dancing lights that stand out in the dark.

Jellyfish with their own light

Fish are not the only inhabitants of the sea capable of emitting light. Certain species of jellyfish have a very particular bioluminescence; they emit intermittent flashes of light that come from specialized cells located in the endoderm—the internal tissue of the jellyfish. Thanks to the fact that its body is practically transparent, it acts as a diffuser, and that light is visible from the outside, highlighting the bright points, and drawing the entire body of the jellyfish in the dark.

More specifically, light sources are often found at the base of the tentacles and along the inner edge of the umbel. It is assumed that the function of bioluminescence in jellyfish has a function of defense and dissuasion from possible predators.

A surprising peculiarity of jellyfish is the ability to emit light without the need for oxygen. As the luciferin reaction is an oxidation, this fact represents a fascinating evolutionary process. The reaction of luciferin from jellyfish, which is called coelenterazine, is mediated by calcium ions. Animals, in the presence of oxygen, accumulate a peroxidized and stable version of the reagent —peroxycoelenterazine—, and then they only need calcium to emit light, even without oxygen in the medium.

the vampire squid

 

Among cephalopods there are also cases of bioluminescence, perhaps the most fascinating being the vampire squid (Vampyroteuthis infernalis). Despite its name, this cephalopod, which is neither an octopus nor a squid, has notable differences from them. On the one hand, the number of arms; it has eight and not ten, it can regenerate them if it loses them, the inner part is covered with spines instead of suckers, and they are connected to each other by a membrane. Additionally, it has two long retractable filaments that are unique among cephalopods.

The luminescent organs of the vampire squid are located under the skin, called photophores, they are located mostly at the end of the arms. The skin has a series of transparent, lens-shaped cells that stretch or compress thanks to the muscles of the skin, opening or closing the passage of light.

On the one hand, this animal can use light as a bait to attract its prey. However, perhaps the most surprising thing about the vampire squid is its defense system. Instead of ink, it emits a mucous and sticky substance, loaded with bioluminescent particles. When attacked, the vampire squid takes the opportunity to wrap its arms around itself, exposing a black and spiny surface to avoid being devoured, at the same time, it emits this shiny mucus, which adheres to the hunter, dazzling it, giving it away to other possible prey. , and making it, at the same time, an easy prey for other predators to see.

Ctenophores, lights and rainbows

 

Almost half of the ctenophore species are bioluminescent. Although this strange group of animals does not contain more than 170 known species.

Alien-looking, these animals are reminiscent of the creatures in James Cameron's famous 1989 film The Abyss. In addition to emitting their own light through bioluminescence reactions, their eight rows of locomotive cilia seem to project the colors of the rainbow.

Although many claim that these rows of changing colors are also the product of bioluminescence, however, it is not a phenomenon of light emission, but of diffraction. The same type of diffraction that Newton discovered by passing a beam of white light through a prism. Indeed, these cilia diffract the white light that the ctenophore receives from the environment, changing its color depending on the orientation of the cilia —and it also changes depending on where you look at it from.

The bioluminescence of ctenophores is dim, blue or greenish in color, and is only visible when in great darkness.

 

Link: https://www.muyinteresante.es/naturaleza/articulo/5-animales-que-brillan-en-la-oscuridad-361655203485