We know, that upon the occurrence of the dark, fireflies begin to emit light. In addition to them, the same phenomenon can be seen at sea – plankton begins to glow there. But how does this glow work and why do living beings need it?
When any living organism starts to glow, it is called bioluminescence. But it is necessary to distinguish this phenomenon from “artificial” bioluminescence, when the animal is specially introduced genes that encode luminous proteins. For example, earlier scientists have already obtained fish and cats glowing in the dark.
Unlike “artificial”, natural luminescence is due to the production of special proteins in special organs of animals. In multicellular organisms, such as a firefly, this organ is called a photophore, while in unicellular organisms, proteins are produced in special organelles inside the cell or directly in its internal environment – the cytoplasm.
However, these proteins do not glow constantly – there are special chemical reactions for this. And they are different for all organisms. The most commonly used light-emitting protein in living beings is luciferin. Under the influence of oxygen, it is converted to oxyluciferin. As a result of this process, energy is released, which is not converted into heat, as usual, but into light. The reserves of this protein are depleted every night, but the body replenishes them quickly enough.
Living beings use bioluminescence for completely different purposes. The glow helps to lure prey and, in some cases, scare away predators. Also, the glow is used by many creatures to communicate with each other or warn of danger. Some people use this property for masking: when there is a lot of light around, dark objects stand out, so it is beneficial for them to “blend” with the background, also highlighting the light.