The sight of a firefly, its warm bioluminescence glow pulsing on and off on a dark summer’s night seems magical. Fireflies (also know as lightning bugs) are not the only living creatures that are known to emit light from their bodies.
In the depths of the vast oceans and in the darkest of caves, there exist living organisms that have adapted themselves to the darkness. These living organisms that radiate light from their bodies and have adapted to their dark environment. These are bioluminescent creatures.
What Is Bioluminescence?
Bioluminescence is a biological process through which light is produced and emitted by a living organism resulting from a chemical reaction occurring within the body of the organism.
Bioluminescence is not a rare phenomenon in marine life. Nature has its own way of putting up a magnificent show of light where sunlight cannot penetrate. The depths of the oceans are home to a variety of bioluminescent species of fish, bacteria, fungi and plants. Bioluminescent creatures on land such as fireflies, glow worms and fungi, in comparison, are a rare occurrence.
What Is Bioluminescence?
Bioluminescent light is a cold source of light so only a fractional amount of this light, (never more than 20%), radiates heat. While some creatures emit bioluminescent light constantly, others choose to emit it or flash it only when needed. Bioluminescent light is usually bluish green in color because most marine organisms show sensitivity to blue and green light and they cannot process colors such as yellow, violet and red. Blue and green light travels well through water.
The Functions Of Bioluminescence
The evolution of the earth’s living creatures is based that no natural physical development occurs without a reason. Similarly, the process of bioluminescence occurs to fulfill the need for certain living organisms to survive in their environmental conditions.
The functions of bioluminescence are:
1. To attract a mate during mating season
2. To detect prey
3. To lure prey
4. To defend oneself against a predator
5. To communicate between similar species
6. To navigate
The Chemistry Of Bioluminescence
The process of bioluminescence requires the presence of two chemicals, a pigment called luciferin and an enzyme called luciferase. When luciferin reacts with oxygen in the presence of the catalyst luciferase, a by product known as oxyluciferin is produced. This oxyluciferin is the luminescent light which is emitted by bioluminescent creatures.
However, it has been recently identified that some bioluminescence processes do not involve the enzyme luciferase. These reactions occur by combining a chemical called photo protein with the help of an ion of calcium to produce light.
The pigment luciferin is self synthesized in certain organisms; although other organisms may absorb it by consumption of food or by sharing a symbiotic relationship with another organisms. The color that is generated in bioluminescent organisms results from the arrangement of molecules of luciferin.
Bioluminescence In Humans
As vague as bioluminescence in humans may sound, recent scientific research has successfully proven that the human body emits very low intensity light which is invisible to the naked eye. Japanese scientists Daisuke Kikuchi and Masaki Kobayashi from the Tohoku Institute of Technology are the minds behind the proof of bioluminescence in humans.
With the aid of a highly sensitive imaging CCD (charge-coupled device) camera, these researchers were able to capture the very first images of human bioluminescence. It is no secret to science that living organisms are capable of producing negligible amounts of light resulting from cellular chemical reactions; however, capturing this low intensity bioluminescent light from humans was considered as an impossible feat. Nevertheless, this recent achievement comes as a breakthrough in the field of biology.
Dr. Gary Schwartz has also conducted experiments where he detected and recorded biophotons from plants and humans.
Experimenting Bioluminescence In Humans
Researchers Daisuke Kikuchi and Masaki Kobayashi used a very sensitive CCD camera to observed the upper bodies of the volunteers over a period of days.
The startling observations made during the process of this experiment include:
1. The human body emits light which is invisible to the naked eye; this light is precisely a 1000 times weaker than the human eye can perceive.
2. The human body emits light rhythmically and directly.
3. The light emitted by the human body is at its highest intensity late in the afternoon and it is at its lowest intensity late at night.
4. The forehead, cheeks and neck are the areas of the human body from which light of the brightest intensity is emitted as compared to other body parts.
5. It was also noted that the brightest areas noticed upon thermal imaging of the human body did not correspond with the brightest areas on these images of human bioluminescence.
Just as bioluminescence occurs due to chemical metabolic reactions in other known bioluminescent creatures, bioluminescence occurs in humans due to metabolic reactions as well. When cells of the human body respire, they produce highly reactive free radicals. These free radicals interact with free floating protein and lipids. This reaction can, at times, lead to further interaction with fluorophores in the human body, which leads to the emission of light.
Since human bioluminescence occurs at such a low intensity, it is very unlikely that this feature will serve any evolutionary purpose. Probably upon further research and study of this phenomenon, the practical applications of human bioluminescence may develop.