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I read that Japanese researchers have developed very sensitive camera that recorded bioluminescence in humans; is it possible and if so what is the mechanism behind it?
From the article you linked:
virtually all living organisms emit extremely weak light, spontaneously without external photoexcitation. This biophoton emission is categorized in different phenomena of light emission from bioluminescence, and is believed to be a by-product of biochemical reactions in which excited molecules are produced from bioenergetic processes that involves active oxygen species
They reference these two works. The first is a 1988 review from Popp et al. (1988):
Biophoton emission - Experientia 44:543-600. (sorry, I cannot find the link to a full text… )
Fritz-Albert Popp is the biophysicist who first developed the biophoton theory.
The second work they reference is by the same first author:
In vivo imaging of spontaneous ultraweak photon emission from a rat's brain correlated with cerebral energy metabolism and oxidative stress. - Kobayashi M, et al.
Finally, a search in Pubmed reveals various other articles by different authors studying different species.
Why is Bioluminescence used? Why Bioluminescence is important?
Production and emission of light by a living organism is called Bioluminescence. Bioluminescence is found in a wide range of organisms, including vertebrates and invertebrates. Bioluminescent organisms have luminescent bacteria that are capable of producing light by chemical reactions (this is the reason bioluminescence is considered to be a form of chemiluminescence). Two molecules are produced by the organisms, luciferin (a pigment) and luciferase (an enzyme). Chemiluminescence can occur both within as well as outside the cell.
Different organisms use bioluminescence in different ways few uses are listed below &ndash
- Bioluminescence widely occurs in marine vertebrates and invertebrates. They use bioluminescence to lure prey or search for prey. Fishes like the anglerfish is a predator which uses bioluminescence to lure its prey.
- Viperfish has a long dorsal spine that is tipped with a photophore (where bioluminescence occurs). Like the Anglerfish, Viperfish also uses bioluminescence to lure prey. Viperfish further uses bioluminescence for camouflaging from its predators. Bioluminescence is also used by the Viperfish to attract mates.
- Above the water on ground bioluminescence is used by the adult fireflies also called lightning bugs to attract mates.
After understanding how organisms have been using bioluminescence to their advantage, let&rsquos look at its importance as well. Bioluminescence plays a vital role in the survival of the deep sea animals. With the fainting light which is filtered from the top of the sea, bioluminescence helps marine organisms to blend easily with the surface of the seabed. This helps them in concealing from the predators which are generally above them.
Fishes like the viperfish leave themselves motionless and then use bioluminescence to remain safe from the predators. At the same time, bioluminescence helps them in attracting small fishes towards them. They have a hinged shaped head which they can move upwards when required. As soon as a small fish gets attracted due to bioluminescence and comes close enough to the fish they attack them.
Squid is another marine organism which uses bioluminescence wisely. The luminescent bacteria reside in the mantle cavity of the squid. Squid uses this for self-defense in the deep sea. It is believed that squid confuses and frightens the organisms trying to attack it by releasing black colored ink.
There have been a lot of researchers related to bioluminescence. The most important one is where the scientists have tried to produce a glowing rabbit. Scientists have yet to discover a lot about the chemicals which synthesis and emit light. It is believed that understanding the reaction more, could open new doors in medical science and it is thought that bioluminescence would be capable of curing diseases as big as AIDS. However, these studies are yet to be completed as bioluminescence is majorly present in the marine organisms which live in deep seas. These animals are very difficult to be found. Apart from that as their natural habitat has low temperatures and high water pressures they don&rsquot survive longer when captivated.
What is Bioluminescence?
The current paper main focus is on bioluminescent Fungi but the basic features of bioluminescence discussed are common to all bioluminescent organisms. Bioluminescence is simply light created by living organisms. Probably the most commonly known example of bioluminescence by North Americans is the firefly, which lights its abdomen during its mating season to communicate with potential mates. This bioluminescent ability occurs in 25 different phyla many of which are totally unrelated and diverse with the phylum Fungi included in this list (an illustration of a bioluminescent fungi is displayed in figure 1). One of the features of biological light that distinguishes it from other forms of light is that it is cold light. Unlike the light of a candle, a lightbulb, bioluminescent light is produced with very little heat radiation. This aspect of bioluminescence especially interested early scientists who explored it. The light is the result of a biochemical reaction in which the oxidation of a compound called "Luci
ferin" and the reaction was catalyzed by an enzyme called "Luciferase". The light generated by this biochemical reaction has been utilized by scientists as a bioindicator for Tuberculosis as well as heavy metals. On going research involving bioluminescence is currently underway in the areas of evolution, ecology, histology, physiology, biochemistry, and biomedical applications.
History of Bioluminescent Fungi
The light of luminous wood was first noted in the early writings of Aristotle which occurred in 382 B.C.(Johnson and Yata 1966 and Newton 1952) The next mention of luminous wood in the literature occurred in 1667 by Robert Boyle who noticed glowing earth and noted that heat was absent from the light. Many early scientists such as Conrad Gesner, Francis Bacon, and Thomas Bartolin all observed and made notation of luminous earth(Johnson and Yata 1966 and Newton 1952 ). These early observers thought that the light was due to small insects or animal interactions. The first mention that the light of luminous wood was due to fungi occurred from a study of luminous timbers used as supports in mines by Bishoff in 1823. This opened the way for further study by many other scientists and by 1855 modern experimental work began by Fabre ( Newton 1952). Fabre established the basic parameters of bioluminescent fungi, those being:
· The light without heat
· The light ceased in a vacuum, in hydrogen, and carbon dioxide
· The light was independent of humidity, temperature, light, and did not burn any
brighter in pure oxygen
The work by Herring (1978) found that the luminescent parts of the included pileus(cap), hymenium(gills) and the mycelial threads in combination or separately(figure 2) also the individual spores were also seen to be luminescent. Herring also stated that if the fruiting body (mushroom) was bioluminescent then the mycelial threads were always luminescent as well but not vice versa.
From the 1850's to the early part of the 20th century the identification of the majority of fungal species exhibiting bioluminescent traits was completed. The research of bioluminescent fungi stagnated from the 1920's till 1950's (Newton 1952 and Herring 1978 ). After which extensive research began involving the mechanisms of bioluminescence and is still carried out to the present.
The Process of Bioluminescence
Bioluminescence results because of a certain Biochemical reaction. This can be described as a chemiluminescent reaction which involves a direct conversion of chemical energy transformed to light energy( Burr 1985, Patel 1997 and Herring1978). The reaction involves the following elements:
· Enzymes (Luciferase) - biological catalysts that accelerate and control the rate of chemical reactions in cells.
· Photons - packs of light energy.
· ATP - adenosine triphosphate, the energy storing molecule of all living organisms.
· Substrate (Luciferin) - a specific molecule that undergoes a chemical charge when affixed by an enzyme.
· Oxygen - as a catalyst
A simplified formula of the bioluminescent reaction:
ATP(energy) + Luciferin (substrate)+ Luciferase(enzyme) + O2(oxidizer) == == light (protons)
The bioluminescent reaction occurs in two basic stages:
1) The reaction involves a substrate (D-Luciferin), combining with ATP, and oxygen which is controlled by the enzyme(Luciferase). Luciferins and Luciferase differ chemically in different organisms but they all require molecular energy (ATP) for the reaction.
2) The chemical energy in stage one excites a specific molecule (The Luminescent Molecule: the combining of Luciferase and Luciferin). The excitement is caused by the increased energy level of the luminescent molecule. The result of this excitement is decay which is manifested in the form of photon emissions, which produces the light. The light given off does not depend on light or other energy taken in by the organism and is just the byproduct of the chemical reaction and is therefore cold light.
The bioluminescence in fungi occurs intracellulary and has been noted at the spore level(Burr 1985, Newton 1952 and Herring 1978). This may at times be mistaken for a extracellular source of light but this is due to the diffusion of the light through the cells of the fungus. In examining the photograph in figure 1, it appear that the cap of the fungus is glowing but after study, it was observed that just the gill structures that emits the light and the cap (which is thin) emits the light of the gills by diffusion(Herring 1978).
The energy in photons can vary with the frequency (color) of the light. Different types of substrates(Luciferins) in organisms produce different colors. Marine organisms emit blue light, jellyfish emit green, fireflies emit greenish yellow, railroad worms emit red and fungi emit greeny bluish light (Patel 1997).
Fungal Families Exhibiting Bioluminescence
The phylum Fungi is composed of the following 5 divisions (Newton 1952):
· Myxomycetes (slime molds)
· Schizomycestes (bacteria)
· Phycomycetes (moulds)
· Ascomycetes ( yeasts, sac fungi and some molds)
· Basidiomycetes (smuts, rusts, and mushrooms)
Of the above divisions the majority of bioluminescence occurs in the Basidiomycetes and only one observation has been made involving the Ascomycetes specifically in the Ascomycete genus Xylaria (Harvey 1952). At present there are 42 confirmed bioluminescent Basidiomycetes that occur world wide and share no resemblance to each other visually, other than the ability to be bioluminescent. Of these 42 species that have been confirmed 24 of these have been identified just in the past 20 years and as such many more species may exhibit this trait but are yet to be found.
The two main genus that display bioluminescence are the genus Pleurotus which have at present 12 species which occur in continental Europe and Asia. The genus Mycena have 19 species identified to date with a world wide distribution range. In North America only 5 species of bioluminescent basiodiomycetes have been reported. These include the Honey mushroom -Armillaria mellea (illustrated in figure 3), the common Mycena -Mycena galericulata (illustrated in figure 1), the Jack O'Latern - Ophalalotus olearius (pictured in figure 4), Panus styticus and Clitocybe illudens.
The question of whether bioluminescent mushrooms were all poisonous was raised in the discussions between my laboratory partner and myself. After examining the literature and a mushroom field guide book it was evident that there was no correlation between the edibility of the mushroom and its bioluminescence. Some mushrooms such as Armillaria mellea the Honey mushroom was listed as being excellent to eat. While the Jack O'Latern - Omphalalotus olearius was listed as poisonous and caused sever gastrointestinal cramps. The edible merits of the common Mycea were unknown and while Panus stypticus was listed as poisonous it was found to contain a clotting agent and useful in stopping bleeding (Lincoff 1981, Newton 1952 and Herring 1978). As it only a field guide to North American mushrooms was available, only the North American varieties were examined. If all 42 species of bioluminescent basidiomycetes were included in the search, a possible correlation may have been found.
Bioluminescence Research Applications
Luminescence has a unique advantages for scientific studies as it is the only biochemical process that has a visible indicator than can be measured. The light given off in the bioluminescent reaction is now able to be accurately measured with the use of a luminometer. This ability to easily and accurately detect small amounts of light has led to the use of the bioluminescent reaction in scientific research involving biological process applications. The following are just a few applications, some of which have been developed in only the last few years (Johnson and Yata 1966, and Patel 1997). The following are two examples of which have been recently developed.
The Tuberculosis Test
Testing for tuberculosis has long been a problem because of the long time it takes for the species to grow to a size that is detectable by modern medicine. Typically growing a culture of Mycobacterium tuberculosis large enough to determine the strain that a particular patient has can take up to three months. Of course, this poses a problem because the patient often can not wait for the diagnosis and must be given drugs that his strain may be resistant to. This is further complicated because there are 11 drugs used to combat TB, picking the right one before determining the strain has a 1/11 chance of success. Recently a way of incorporating bioluminescence into the TB tests has been found and can sharply reduce the diagnosis time to as little as 2 days. The technique involves inserting the gene that codes for luciferase into the genome of the TB bacterial culture taken from the patient. The gene is introduced through a viral vector and once incorporated, the bacteria produces the luciferase. When luciferin i
s added to the culture, light is produced. Since less than 10,000 bacteria are needed to code for enough luciferase to produce a detectable amount of light, the culture time is reduced to only 2-3 days. Since the luciferase-luciferin reaction requires ATP, the resistance of the strain in the culture can be tested by adding a drug and watching for light. This will indicate which of the 11 drugs therapy's will be effective in treating Tuberculosis. By reducing the time needed to prescribe the correct drugs for treatment, this application of bioluminescence will someday be ready to save some of the 3 million killed each year by tuberculosis (Patel 1997).
Bioluminescence has also been used for several years as a biosensor of many substances. As seen in the tuberculosis example, bioluminescence can be used a sensor for the presence of ATP because ATP is needed in the light producing reaction. Other techniques have been used for detecting ions of mercury and aluminum, among others, by using bacteria with light genes fused to their ion-resistant regulons. For example, if a bacteria that is resistant to Hg is in the presence of Hg, the genes coding for its Hg resistance will be activated. The activation of that gene will also activate the luciferase gene fused to it, so the bacteria will produce luciferase whenever Hg is present. Adding luciferin and testing for light production with a luminometer reveals the presence of the metal ion in the solution. This technique is especially useful in testing for pollutants in the water supply when concentrations are too low to detect by conventional means(Herring 1978, and Patel 1997).
Other areas that are currently using bioluminescence in scientific research include evolution, ecology, histology, physiology, biochemistry, biomedical applications, cytology and taxonomy. Any area that involves a living organism can utilize bioluminescent technology as a biosensor.
The glow light generated by bioluminescent Fungi has for centuries generated interest from philosophers and scientists and has benefited science by providing problems to solve -How does it work and does it have a practical application? The answers to those basic problems that have been discovered today and have resulted in benefiting mankind, by bettering our lives especially in regard to it's biomedical applications. Further research with bioluminescent Fungi is being conducted on a world wide scale and include North America, Japan, and Europe. Future research may lead to new discoveries and uses from bioluminescent organisms such as the Fungi group.
Burr, G.J. 1985. Chemiluminescence and Bioluminescence. Marcel Dekker, Inc. New
Johnson, F. H. and Yata, H. 1966. Bioluminescence in progress. Princton, New
Jersey, Princeton University Press.
Laboratory Methods in Cell Biology
5.2 Step 2—Substrate Luciferin Administration
|Overview||Substrate luciferin needs to be administered to mice minutes before BLI.|
|Duration||Lasts up to 15 min.|
|2.1||After the mouse is fully anesthetized, inject the mouse intra-peritoneally (i.p.) with the luciferin solution (40 mg/mL in PBS) at a dose of 200 mg/kg body weight 5–15 min before imaging.|
|Caution||If more than one mouse are imaged simultaneously, luciferin injection for each mouse should be performed as fast as possible so that all mice are administered with the substrate at about the same time.|
|Careful and consistent luciferin injection in terms of the amount and the location of injection is required in BLI analyses over time.|
|Tips||For the injection, mice should be manually restrained, abdomen side up. Needles should be level-side up and slightly angled when entering the abdominal cavity. The tip of the needle should just penetrate through the abdominal wall (about 4-5 mm) of the animal’s left lower abdominal quadrant.|
|The luminescent signal intensities increase with increased amounts of substrate luciferin administered within a certain range. In general, at least 100 μg/g body weight of luciferin is needed to generate a significant amount of emission of luminescence from the liver region where the luciferase-expressing cells are. Luciferin administration at 100–400 μg/g body weight results in a dose-dependent increase in luminescence emitted ( Chen & Kaufman, 2004 ).|
|The magnitude of bioluminescence measured varied with time after the injection of luciferin. A Luciferin kinetic study should be performed for each animal model to determine peak signal time after Luciferin administration. For example, luminescence can be detected in the liver region from the dorsal side of the mouse as early as 2 min after the administration of luciferin. The luminescence intensity peaks around 10 min, diminishes rapidly within the first hour and completely disappeared by 3–4 h.|
See Fig. 3 for the flowchart of Steps 1 and 2.
FIGURE 3 . Flow chart of protocol Steps 1 and 2.
At least 1,500 species of fish are known to be bioluminescent, including sharks and dragonfish—and scientists regularly discover new ones.
Among the most iconic are deep-sea fishes like the anglerfish, whose females sport a lure of glowing flesh that acts as bait for any prey close enough to be snatched.
Hawaiian bobtail squid light up via bioluminescent bacteria living in one of their organs the light camouflages them against moonlight on the surface and eliminates their shadow, obscuring them from predators. (Read about nature’s living fireworks—animals that bioluminesce.)
If you shine a light on a comb jelly, light refracted off its moving cilia might be mistaken for bioluminescence.
Their true bioluminescence cannot be seen in light, says marine biologist Edie Widder, founder of the Ocean Research and Conservation Association. Their real bioluminescence comes from light-producing chemicals which different species use in different ways, such as flashing the chemicals to deter predators.
Then there’s the world’s smallest shark, the six-inch lanternshark, which advertises its own goods via photophores (or light-producing organs) clustered around its reproductive organs.
Males and females are “strutting their stuff, showing where their stuff is,” says George Burgess, formerly of the Florida Museum of Natural History. Each species has a specific light pattern, “like a name tag,” so they can find mates in the dark ocean depths, he adds.
Why Animals Light Up
The yellow bioluminescent ring on this female octopus may attract mates. (Michael Vecchione/NOAA)
Animals can use their light to lure prey towards their mouths, or even to light up the area nearby so that they can see their next meal a bit better. Sometimes the prey being lured can be small plankton, like those attracted to the bioluminescence around the beak of the Stauroteuthis octopus. But the light can also fool larger animals. Whales and squid are attracted to the glowing underside of the cookie-cutter shark, which grabs a bite out of the animals once they are close. The deep-sea anglerfish lures prey straight to its mouth with a dangling bioluminescent barbel, lit by glowing bacteria.
Syllid fireworms can be found mainly on the seafloor, but they switch to a planktonic form to reproduce, where the females use bioluminescent signals. (© 2010 Moorea Biocode)
Animals don't only need to look for and attract food bioluminescence can also play a part in attracting a mate. The male Caribbean ostracod, a tiny crustacean, uses bioluminescent signals on its upper lips to attract females. Syllid fireworms live on the seafloor, but with the onset of the full moon they move to the open water where the females of some species, like Odontosyllis enopla, use bioluminescence to attract males while moving around in circles. These glowing worms may have even helped to welcome Christopher Columbus to the New World. Anglerfish, flashlight fish and ponyfish all are thought to luminesce in order to tell the difference between males and females, or otherwise communicate in order to mate.
This fish is using counterillumination to disappear. At left it stands out against the light above it. At right, with bioluminescent structures lit, it blends in. (Smithsonian Institution)
Often animals use a strong flash of bioluminescence to scare off an impending predator. The bright signal can startle and distract the predator and cause confusion about the whereabouts of its target. From small copepods to the larger vampire squid, this tactic can be very useful in the deep-sea. The "green bomber" worm (Swima bombiviridis) and four other similar worm species from the polychaete family release a bioluminescent "bomb" from their body when in harms way. These deep sea worms live close to the sea bottom and were only discovered in 2009. Some animals such as the deep-sea squid Octopoteuthis deletron even detach their bioluminescent arms, which stick to and probably distract their predators. All this commotion could also serve as a burglar alarm, attracting larger predators to the scene. In certain cases a predator might only get a bite of their prey, and the evidence will keep glowing from within its stomach.
Bioluminescence can also be used to help camouflage with the use of counterillumination. Photophores on the bottom side of an animal can match the dim light coming from the surface, making it harder for predators searching for prey from below to see what they are looking for.
Bioluminescence and humans
Throughout history, humans have devised ingenious ways of using bioluminescence to their advantage. Glowing fungi have been used by tribes to light the way through dense jungles, for example, while fireflies were used by miners as an early safety lamp. Perhaps inspired by these applications, researchers are now again turning to bioluminescence as a potential form of green energy. In the not so distant future, our traditional street lamps may be replaced by glowing trees and buildings.
Today, bioluminescence from Aliivibrio fischeri is used to monitor water toxicity. When exposed to pollutants, light output from the bacterial culture decreases, signalling the possible presence of a contaminant.
Bioluminescence has even played a part in warfare. Bioluminescent organisms aided in the sinking of the last German U-boat during World War One, in November 1918. The submarine is reported to have sailed through a bioluminescent bloom, leaving a glowing wake which was tracked by the allies.
It has had a protective role too. In the aftermath of one of the bloodiest battles of the American Civil War, at Shiloh, the wounds of some of the injured soldiers began to glow. These glowing wounds healed more quickly and cleanly, and the phenomenon became known as “Angel’s Glow”. The glow was probably produced by Photorhabdus luminescens, a soil-dwelling bacterium which releases antimicrobial compounds and so protected the soldiers from infection.
It is perhaps the medical applications of bioluminescence that have attracted the most excitement. In 2008, the Nobel Prize in Chemistry was awarded for the discovery and development of green fluorescent protein (GFP). GFP is found naturally in the crystal jellyfish Aequorea victoria, which, unlike the bioluminescence mechanism described so far, is fluorescent. This means that the protein needs to be excited by blue light before emitting its characteristic green light. Since its discovery, GFP has been genetically inserted into various cell types and even animals to shed light on important aspects of cell biology and disease dynamics.
The evolutionary process that culminated in bioluminescence may have taken million of years, but its scientific applications continue to revolutionise our modern world. Remember that, the next time you see the sea sparkle.
One example of bioluminescent algae is a dinoflagellate called Noctiluca, or sea sparkle. Noctiluca are so small that thousands of them can fit in a single drop of water.
Noctiluca viewed through a microscope. Image by Maria Antónia Sampayo
In places like Bioluminescent Bay in Puerto Rico, an island in the Caribbean, sea sparkle are so abundant that the water sparkles neon blue at night when you run your hand or a kayak paddle through it!
Scientists think that Noctiluca flashes to startle or scare away its predators. The bioluminescence might also attract bigger predators to eat Noctiluca’s predators, just like a burglar alarm that alerts the police to come to someone’s house to catch a robber.
Although some Noctiluca are big enough to be seen without a microscope, most are too small for you to see unless you notice their flash. Some tiny animal plankton (zooplankton) can also glow in the dark, though, and they are big enough to see with the unaided eye.
Strange! Humans Glow in Visible Light
The human body literally glows, emitting a visible light in extremely small quantities at levels that rise and fall with the day, scientists now reveal.
Past research has shown that the body emits visible light, 1,000 times less intense than the levels to which our naked eyes are sensitive. In fact, virtually all living creatures emit very weak light, which is thought to be a byproduct of biochemical reactions involving free radicals.
(This visible light differs from the infrared radiation &mdash an invisible form of light &mdash that comes from body heat.)
To learn more about this faint visible light, scientists in Japan employed extraordinarily sensitive cameras capable of detecting single photons. Five healthy male volunteers in their 20s were placed bare-chested in front of the cameras in complete darkness in light-tight rooms for 20 minutes every three hours from 10 a.m. to 10 p.m. for three days.
The researchers found the body glow rose and fell over the day, with its lowest point at 10 a.m. and its peak at 4 p.m., dropping gradually after that. These findings suggest there is light emission linked to our body clocks, most likely due to how our metabolic rhythms fluctuate over the course of the day.
Faces glowed more than the rest of the body. This might be because faces are more tanned than the rest of the body, since they get more exposure to sunlight &mdash the pigment behind skin color, melanin, has fluorescent components that could enhance the body's miniscule light production.
Since this faint light is linked with the body's metabolism, this finding suggests cameras that can spot the weak emissions could help spot medical conditions, said researcher Hitoshi Okamura, a circadian biologist at Kyoto University in Japan.
"If you can see the glimmer from the body's surface, you could see the whole body condition," said researcher Masaki Kobayashi, a biomedical photonics specialist at the Tohoku Institute of Technology in Sendai, Japan.
The scientists detailed their findings online July 16 in the journal PLoS ONE.
Bioluminescence Questions and Answers
Here are answers to 10 common questions about bioluminescence:
What are some of the different animals that make light?
Although bioluminescence may be considered rare as measured by the total number of species, it is extremely diverse in its occurrence. There are many different types of organisms that produce bioluminescence, from microscopic cells to fish and even a few sharks. But there are no luminescent animals in higher vertebrates above the fish. Overall, luminescent organisms represent most of the major phyla.
Let’s go through a short list of groups that have luminescent members (rare means that only a few species are luminescent). The most common are highlighted with an asterisk (*):
- Single celled organisms:
- *Coelenterates and Ctenophores (jellyfish): siphonophores, medusae, soft corals, (comb jellies)
- Gastropods: nudibranchs (rare), clams (rare), *squids, octopus (rare)
- Annelids (worms): *polychaetes (bristle worms), earthworms
- *Marine crustaceans: mysids (rare), copepods, ostracods (firefleas), amphipods, krill, shrimp
- Insects: *beetles (fireflies, glowworms), flies (rare), centipedes (rare), millipedes (rare)
- Echinoderms:, sealilies, seastars, *brittlestars, sea cucumbers
- *Tunicates: pyrosomes, larvaceans
- Sharks (rare)
- *Fishes – many different types
Why are so many animals in the ocean bioluminescent?
Probably bioluminescence originated in the oceans based on the chemical structures of luciferins and luciferases, bioluminescence may have independently evolved several dozen times.
Light emission is functionally important only if it is detected by other organisms. There are several reasons why bioluminescence is an effective means of communication in the ocean.
- First, in a large part of the ocean the transmitted sunlight is dim or absent, so bioluminescence becomes an alternative way to communicate using light.
- Second, the volume of habitat where bioluminescence is effective is vast, allowing natural selection to take place in a huge ecological context.
- Third, in most of the ocean there is no concealment, so animals “hide in the wide open.”
Some of the most common functions of bioluminescence in the ocean are for defense against predators or to find or attract prey. In the deep ocean, where sunlight is dim or absent, more than 90% of the animals are luminescent.
Did you know that a small luminescent deep-sea fish called the bristlemouth lightfish is considered the most abundant vertebrate on the planet?
Are bioluminescent animals found only in the ocean?
No. There are luminescent land animals, but they are relatively rare compared to those in the ocean. If you live east of the U.S. continental divide you may be familiar with the dusk displays of fireflies during the summer.
There are so-called railroad worms in South and Central America, which are actually beetle larvae. Their name comes from the rows of green and red lights coming from each body segment. Some mushrooms glow, as does a land snail from Malaysia, and some earthworms, millipedes, centipedes, and nematodes.
With the exception of one animal related to a clam, there are no luminescent freshwater animals.
So in general bioluminescence on land and in freshwater is rare compared to its occurrence in the ocean. We can only guess at why luminescence does not occur in freshwater environments. There are freshwater habitats with low light levels like in the deep sea but with no bioluminescence. Perhaps there is a chemical requirement that is missing? It is easier to study something that exists than something that doesn’t, so we know much more about why there is bioluminescence in the ocean than why there isn’t bioluminescence in lakes and rivers.
Is the glowworm the same as a firefly?
Glowworms are not worms, but they do glow. Glowworms are actually fly larvae, and they live in caves such as Waitomo Cave in New Zealand. Their glowing attracts insects which get stuck in mucous threads hanging from the ceiling and are then eaten. So in this case, the glowing acts as a lure to attract prey.
What is the function of bioluminescence?
Bioluminescence is important only if it is detected by other organisms. While there are different functions of light emission, and animals can use the light for more than one function, the uses of bioluminescence can be grouped there are several main types:
- Finding or attracting prey
In the dark ocean, dim glowing can be used to attract prey.Fish such as the anglerfish use a light organ filled with bacteria that dangles from their forehead. Prey are attracted to the light in the same way that a fisherman might use a glowing lure for night fishing. When the unlucky prey gets near the anglerfish it is engulfed whole. Some fish use bioluminescence as a flashlight, which is how flashlight fish got their name. They use light, produced by symbiotic bacteria living in an organ below their eyes, to light up potential prey. On land, the glow of glowworms living in caves serves to attract insect prey, which get snared in the glowworms’ sticky mucous threads.Another example is the glow of fungi, which attracts insects not as prey but as a means of dispersing the fungal spores.
- Defense against predators.
Bioluminescence can serve as a decoy.Some squid and shrimp produce a luminescent glowing cloud similar in function to the ink cloud of squid in daylight. When attacked by a predator, scaleworms and brittlestars sacrifice a part of the body that continues to flash as the animal makes its escape. Other animals living in ocean depths where the sunlight is very dim use bioluminescence to camouflage themselves. Their bioluminescence matches the color and brightness of the dim sunlight, and is called luminescent countershading, because it fills in their shadow and makes it harder for them to be detected by predators. Many small plankton use flashes of light to startle their predators in an attempt to interrupt their feeding.
The best known example is the bioluminescence of fireflies, where there is an exchange of flashes between males and females. Females respond to the flashes of flying males, with the eventual result that the male approaches the female for the purpose of mating. To avoid confusion between members of different types of fireflies, the signals of each species are coded in a unique temporal sequence of flashing. Some marine animals such as polychates (bristle worms) use bioluminescence during mating swarms, where the males will attract females to them. In others such as ostracods (firefleas), males flash in a sequence as they swim to attract females.
Do all jellyfish make light? What is the function of jellyfish bioluminescence?
It is estimated that about 50% of jellyfish are bioluminescent. There are many different types represented, including siphonophores (related to the Portuguese man-o-war), medusae, sea pens and other soft corals, and ctenophores (comb jellies). The greatest diversity of luminescent jellyfish occurs in the deep sea, where just about every kind of jellyfish is luminescent. Most jellyfish bioluminescence is used for defense against predators. Jellyfish such as comb jellies produce bright flashes to startle a predator, others such as siphonophores can produce a chain of light or release thousands of glowing particles into the water as a mimic of small plankton to confuse the predator. Others produce a glowing slime that can stick to a potential predator and make it vulnerable to its predators. Some jellyfish can release their tentacles as glowing decoys. So you see that there are many strategies for using bioluminescence by jellyfish.
Some of the most amazing deep-sea jellyfish are the comb jellies, which can get as large as a basketball, and are in some cases so fragile that they are almost impossible to collect intact.
Also spectacular are the siphonophores, some of which can reach several meters in length. Siphonophores deploy many tentacles like a gill net casting for small fish.
How do animals use chemistry to make light?
All bioluminescence comes from energy released from a chemical reaction. This is very different from other sources of light, such as from the sun or a light bulb, where the energy comes from heat. In a luminescent reaction, two types of chemicals, called luciferin and luciferase, combine together. The luciferase acts as an enzyme, allowing the luciferin to release energy as it is oxidized. The color of the light depends on the chemical structures of the chemicals. There are more than a dozen known chemical luminescent systems, indicating that bioluminescence evolved independently in different groups of organisms. One type of luciferin is called coelenterazine, found in jellyfish, shrimp, and fish. Dinoflagellates and krill share another class of unique luciferins, while ostracods (firefleas) and some fish have a completely different luciferin. The occurrence of identical luciferins for different types of organisms suggests a dietary source for some groups. Organisms such as bacteria and fireflies have unique luminescent chemistries. In many other groups the chemistry is still unknown. For more information on luminescent chemistry visit the Bioluminescence web site.
Does bioluminescence occur in just one color, or are there different colors? If so, how are the different colors produced?
Bioluminescence does come in different colors, from blue through red. The color is based on the chemistry, which involves a substrate molecule called luciferin, the source of energy that goes into light, and an enzyme called luciferase. In land animals such as fireflies and other beetles, the color is most commonly green or yellow, and sometimes red. In the ocean, though, bioluminescence is mostly blue-green or green. This is because all colors of light do not transmit equally through ocean water, so if the purpose of bioluminescence is to provide a signal that is detected by other organisms, then it is important that the light be transmitted through seawater and not absorbed or scattered. Blue-green light transmits best through seawater, so it is no surprise that this is the most common color of bioluminescence in the ocean.
There are some exceptions to the blue-green/green color rule for ocean bioluminescence. Some worms make yellow light, and a deep-sea fish called the black loosejaw produce red light in addition to blue. We believe the red light functions as an invisible searchlight of sorts, because most animals in the ocean cannot see red light, while the eyes of the black loosejaw are red sensitive. Thus it can use its red light to find prey while the prey wouldn’t even know they are being lit up!
What is a photon?
Light is a form of electromagnetic radiation, like radio or microwaves. Some aspects of light, such as its frequency (color), are based on its wave properties. Light can also be considered a stream of particles called photons, each of which contains energy. This concept is called the quantum theory. So there are two ways to express how much light there is. One is based on energy (in units of watts, joules, or calories, and the other is based on the number of photons. For example, the wavelength of green light is less than 1 millionth of an inch, and the energy of one photon of green light is equivalent to 1 million billionth of a calorie! Even though photons are particles, they are particles of energy and are different from particles in a cell such as molecules.
A typical dinoflagellate flash of light contains about 100 million photons and lasts about a tenth of a second.
Through gene splicing, would any species of plants or animals stand to benefit from an artificially induced bioluminescence capability?
All cells have the ability to produce ultra-low levels of light due to oxidation of organic molecules such as proteins, nucleic acids, etc. Through a very long process of natural selection, the organisms we call bioluminescent have developed the ability to enhance light production through physiological, molecular, anatomical, and behavioral adaptations. All this because the bioluminescence imparts an important ecological advantage to the organism. It is the ecological context that provides the driving force for natural selection.
In order for an organism to use bioluminescence that has been artificially induced, several criteria need to be met: