We all are familiar with the tiny insects glowing in the night on their own. Firefly, a tiny yet very unique creature, is one example of this self-illuminating insect. So, let us try to know all about these amazing creatures and how they do it.
If we see around, it is not only the firefly that has the ability of bioluminescence, but there are many other creatures around us. Starting from microorganisms to terrestrial, there is a wide list of bioluminescent creatures.
Let us learn them in detail, from who they are to how they possess and use their bioluminescence feature in various situations.
What is Bioluminescence?
Bioluminescence is the emission of light by an organism. The phenomenon of bioluminescence takes place in a wide range of creatures, from protozoans to fireflies.
Bioluminescence is a chemical reaction (chemiluminescence) where the conversion of chemical energy to radiant energy with very little heat in the process takes place. Light production is associated with various stages of a creature’s life, from survival to mating. This could be seen in squids that secrete luminous clouds to lead the enemy to confusion and provide time for the creature to escape.
The same principle of light emission can also be used by many of the creatures to attract their prey or lighten the path for them in the ocean’s darkness.
It is said that bioluminescence in the lower creatures, like that of fungi and bacterias, was originally associated with the removal of oxygen, toxic to the primitive types of bacteria that developed during the absence of oxygen atmosphere of the earth.
The metabolic reaction of bioluminescence generally involves the combining of the luciferin with oxygen and subsequently liberating sufficient energy.
Terrestrial Bioluminescent Creatures:
Terrestrial creatures are the creatures with land being their dominant habitat. In simple language, we can say that terrestrial animals live on the land for the majority of the time.
Thus, there are various types of bioluminescent creatures in the terrestrial habitat, but the number is less than those of the aquatic habitat.
Arthropods possess the highest number of bioluminescent creatures when it comes to terrestrial habitat. Various arthropod creatures possess the capability of self-illuminating, and each is different from the other in terms of biochemistry, mechanism, and others.
Some of the good examples of terrestrial bioluminescent creatures are fireflies, Diptera, click beetles, glow worms, certain millipedes and centipedes, annelids, and others.
Let us know about some of these in detail.
In the Diptera, the characteristic of luminescence can be observed in mycitophilidae, commonly known as fungus gnats. The Arachnocampa spp, the Keroplatus spp, and the Orfelia fultonii spp are the species with bioluminescence.
The Orfelia fultoni construct their webs along the side of the banks found in the Appalachian mountains. They emit blue bioluminescence that helps them attract their insects (prey). The light organs of this species are found in the anterior part of the body and the tail associated with large and dark pigmented bodies secreted by mitochondria.
The Arachnocampa Luminosa species also construct their webs, but on the houses’ roofs and they emit bluish-green bioluminescence to attract the prey.
Lastly, the Keroplatus species survive under the fungi and produce a fungus-gnat that feeds on the spores produced by the fungi. Light production and emotion is a part of the hypodermal fat of the body by the proteinaceous granules.
Intriguingly, all these species, despite belonging to the same family, possess different characteristics and mechanisms for bioluminescence.
The biochemistry of the luminescence in the mycitophilidae family consists of two different systems.
Activation of bioluminescence of Arachnocampa species differed from that of the Orfelia. In the Arachnocampa species, the bioluminescence takes place due to the activation by the ATP, whereas in the Orfelia involves a 140 KDa dimeric luciferase and a luciferin binding protein. It releases the luciferin in the presence of reducing agents.
The beetles, Coleoptera, include fireflies, railroad worms, click beetles, and others.
The fireflies emit a yellowish, greenish light from the ventral parts for mating. Fireflies tend to possess a species-specific two process of signaling. The first one, females, while staying stationary on the grass, emit an intense primary signal to attract the flying males towards them of the mating process.
Whereas in the second system, the flying males having properly developed light organs emit a primary signal to which the females respond, further establishing a dialogue.
On the other side, the railroad worms possess a bit different characteristic for bioluminescence. The males are weakly or not luminescent at all; also, the characteristic of bioluminescence in railroad worms is not yet well understood.
Some click beetle species living in the termite mounds use their bioluminescence to attract flying prey towards them. During defense from enemies, they use sudden glows to startle their enemies.
In the beetles, the bioluminescence is generated by specialized photophores.
In simpler mechanism bearing beetles, the light is produced by an enormous oenocyte like cell which lacks neural control. Whereas in complex mechanism bearing beetles like the Photinus and Photuris fireflies, the light organ consists of rosettes of several of thousands of photocytes complicatedly penetrated by the tracheoles with a reflective layer. The tracheoles take care of the supply and transportation of air to the photocytes. Inside the photocytes, luciferase is found associated with the peroxisomes, and the luciferin is found concentrated in the cytoplasmic granules of the insect’s body.
Octopamine was considered the main neurotransmitter in the photophores. Still, after adequate research in the respective field, it was suggested that Nitric oxide is the component responsible for triggering the luminescent activity inside the photocytes.
This process inhibits the respiratory chain and makes the adequate amount of oxygen available for the bioluminescent reaction. This hypothesis is yet remained confirmed, but this is the recent update regarding the respected research.
The biochemistry of the terrestrial firefly is the best known and studied among all the others. It involves benzothiazole luciferin, a 60 kDa luciferase, and activation through ATP. The luciferase catalyzes the reaction for the production of bioluminescence through two steps.
Luciferase catalyzes the activation of luciferin through the esterification of the AMP group of ATP to the carboxyl group of luciferin, along with the liberation of pyrophosphate.
The activated luciferin, luciferyl- adenylate, undergoes oxidation reaction by the molecular oxygen forming cyclic peroxy intermediate, which gets cleaved by producing carbon dioxide and oxyluciferin. This product decays by emitting photons of visible light.
The color of the bioluminescence depends on the interaction between the oxyluciferin with the active site of the luciferase and the energy released by the photon.
After cloning and sequencing of the cDNA of the luciferase present in firefly showed that it consists of a single polypeptide with 550 amino acids with the main N terminal connected to a smaller C terminal. These two domains come closer to form a sandwich substrate, creating a suitable environment for light production.
The cloned luciferase of click beetles and railroad worms provided a polypeptide chain of 542-546 residues of amino acids. Thus the visible quantitative difference among the amino acid composition of luciferases is responsible for the difference in the color of bioluminescence.
Bioluminescence can also be noticed in many marine creatures and is used according to their needs.
Use of Bioluminescence in Today’s Life:
Some of the researchers study the chemicals and enzymes involved in bioluminescence. The research is focused mainly on bringing awareness regarding this specific characteristic found in the creatures.
Scientists are studying the chemicals and enzymes involved in fluorescence activity. They have achieved much success in understanding the mechanism of bioluminescence.
According to the present research and study, bioluminescence characteristics can make life easier and better.
For example, the GFP, i.e., the Green Fluorescent Protein, is also known as a “reporter gene,” is considered very valuable. Reporter Genes are the genes used to trace or locate particular activities or locations. They are attached to other genes being studied to prevent the loss of the gene and keep track.
As mentioned, GFP is a fluorescent protein; thus, it emits a green-colored fluorescence, which helps in the process of tracing to the scientists. It also helps them study the expression of the gene in the cell and its interaction with other chemicals.
Apart from this, bioluminescence is brought to many other uses by researchers nowadays. Many brilliant ideas like bioluminescent trees, crops, and other plants with bioluminescence characteristics can be developed.
Bioluminescent trees could reduce the cost of electricity and therefore light up the streets and necessary public places.
On the other hand, bioluminescent crops or plants could be developed to emit fluorescence whenever in need of nutrients or water, which can prove as an easy way for farmers to carry out agricultural activities and benefit them by reducing the agricultural costs.
Thus, bioluminescence is a very spectacular and mesmerizing characteristic found in organisms and is not less than a miracle in this world. When used in the right way, humankind can also be benefitted a lot from these characteristics, and a notable positive change could be brought in the existing circumstances.