What is Bioluminescence?
Bioluminescence is an amazing natural phenomenon in which an organism produces and emits light due to a chemical reaction where the chemical energy is converted into light energy. The sparkle of fireflies on a summer night is produced as a result of a chemical reaction in their glowing abdomens. Bioluminescence occurs due to a chemoluminescence reaction, where the enzyme luciferase catalyses the pigment luciferin. Energy is utilized in most of the reactions. The reaction takes place inside or outside the cell. Many organisms produce luciferase which helps them to accelerate the rate of reaction. Some organisms bind oxygen with luciferin in a photoprotein. It lights up the moment some ion is present.
In bacteria, the gene expression for bioluminescence is regulated by lux operon. However, bioluminescence is common in sea dwellers. Jellyfish, starfish, crustaceans, squid, sharks are some of the marine organisms that exhibit bioluminescence. Deep oceans have no light. Bioluminescence helps marine animals to survive in such a dark environment. In some fishes, the light is present in front of the mouth which helps them to attract preys. Squids emit bioluminescent fluid to defend themselves from predators. Crustaceans and worms use bioluminescence to attract partners. Bioluminescent organisms can be found from the surface to the seafloor, near the coast, to open ocean. Many planktons such as dinoflagellates bloom on the surface of the water during optimum conditions which make the ocean sparkle at night and provides it with a reddish-brown colour during the day. The Hawaiian Bobtail Squid contains the chemicals that are required to create bioluminescence.
A large number of marine entities show bioluminescence wherein the colour that is emanated is usually green or blue and in a few cases the red colour is also observed. Apart from marine organisms, bioluminescence is also observed in the land entities, precisely invertebrates such as fireflies, worms, larvae – insects. A brief explanation of the organisms exhibiting bioluminescence is given below:
- Dragonfish –
The Black Dragonfish is a scaleless fish which appears monstrous. They are found inhabiting deep in the sea and possess special organs, the photophores that are known to produce light. The organ structures are found in their smallest form along the body whereas larger photophores are located just below the eyes enclosed in a formation that dangles below the barbel. Apart from producing the traditional blue-green colour, they are also capable of producing the red light which helps them find their prey in the dark.
- Dinoflagellates –
Also known as the fire algae, they are a kind of unicellular algae that are found inhabiting both in freshwater and marine ecosystems. These entities are capable of bioluminescence as they produce a chemical compound which has the potential to generate light when they react. The process is stimulated when dinoflagellates come in contact with any object, other organisms or even water movement through waves. They can also glow due to a dip in the temperature. They use the process of bioluminescence as a defensive mechanism from the predators. On lighting up, these entities produce a glowing blue colour.
- Glow-worm –
Contrary to its name, glow worms are not worms inherently, instead, they are larvae of different groups of adult females or insects that have a resemblance to the larvae. The adult versions of these glow-worms do not possess wings, instead, exhibit structures on their abdominal and thoracic areas, wherein these organs emit light. They use the process of bioluminescence to lure their mates and attract their prey such as bugs. They hang suspended to the sticky long fibres they produce wherein the prey are entrapped. In order to warn predators, glow worms emit light that is toxic enough.
- Fungi –
About 70 species of fungi are known to be bioluminescent. They emit green light. For instance, mushrooms glow so as to attract insects. These insects, upon getting attracted, crawl around them picking up spores. In fungi, this process is regulated by a circadian clock which is controlled by temperature. The fungi begin to glow once the sun sets and the temperature drops which, in the dark, are clearly evident to the insects.
- Fire-flies –
Fire-flies possess light-generating structures located in their abdomens wherein light is generated when the chemical luciferin reacts with calcium, oxygen, ATP and the enzyme responsible for the bioluminescence, luciferase, inside the organ. It serves quite a few purposes such as, in adult fire-flies, bioluminescence is used to lure mates and attract prey. The light pattern that flashes is helpful in identifying different members belonging to the same species, also to discriminate between female and male fireflies. In the larvae version of the firefly, it is used as a warning to the predators so as to not consume them as they possess toxic elements. Some other fire-flies have the ability to sync their light emission to a process referred to as simultaneous bioluminescence.
A lot is still unknown about how these species use bioluminescence. Many times, a sudden “turning on” of the lights might scare away potential prey. Many types of bioluminescence are also difficult to observe in visible light. Also, their samples can’t be easily collected for research purposes.
Also read: Camouflage
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