Like most people, you probably think of the deepest parts of the oceans as vast, lifeless deserts frozen in total darkness. Wrong! The ocean depths are a stunning light show full of brilliant colors.
The spectacle of “living light”
Some of these underwater lights glow, others twinkle, shine or flash in multicolor explosions of rockets, sparks, and blue smoke — and others are long streaming chains of luminous dots like paper lanterns…
It’s not a dream or a movie – although it resembles the stunning landscape of the film Avatar – nor is it science fiction: welcome to the real, and extraordinary, world of bioluminous living beings.
We all know about fireflies, those little luminous beetles. They are the most visible and well known of our terrestrial bioluminescent creatures. But thousands more exist at the bottom of the ocean, many yet to be discovered.
Bioluminescence or phosphorescence?
Bioluminescence and phosphorescence are what give living organisms – such as fungus, seaweed, jellyfish, fish, bacteria, coral, plankton, mollusk, worms – the ability to emit light.
- Bioluminescence = the organism produces its own light,
- Biophosphorescence = the organism emits absorbed light.
In 1885, French doctor Raphaël Dubois identified the source of a firefly’s bioluminescence: a chemical reaction between a protein, luciférine and an enzyme, luciférase (1).
Today, we know that bioluminescence results either from “direct production”, or from bacteria which has invited itself into the host organism: host me and I will give you light. Yet another beautiful example of symbiosis between species!
But why do these creatures emit light?
The intelligent light of the living
As beautiful as they can be, these light emissions are actually survival tactics for some terrestrial, and most underwater, species. Bioluminescence and biophosphorescence help species survive in multiple ways:
- Hiding: for some fish, the light they emit serves as camouflage. How? In the ocean, light comes from above and, as a fish swims over a predator hiding below in the shadows, the light it emits mirrors the light above: the fish simply disappears under an “invisibility cloak.”
- Chase: the lantern fish (made famous by the Nemo movie) uses its light to attract prey. Once the prey, attracted by the light, comes near, the fish simply opens his mouth and devours…
- Identify and communicate: as with fireflies that emit flashes at variable intervals to communicate their species and other identifying information
- Frighten predators: by using light to camouflage the creature as “someone else” or to signal to a predator that they are not edible, like millipedes who secrete radioactive cyanide along with their luminosity.
- Reproduce: like the peacock that fans its tail to attract a potential partner, certain species decorate themselves in light. In the case of luminous plankton, they reveal their position to fish so they can be absorbed. Why? Because the womb of the fish offers the perfect conditions for reproduction.
- Disorient the enemy: when threatened, some creatures can blind predators with light and escape
Turn the tables: shine the spotlight on the predator and reverse roles: the prey uses his light to light up the predator, making the predator visible and vulnerable to other predators
It’s pretty, but what else?
Scientists from across the world are working to put this living light to human use, with the promise of numerous useful applications.
ATP test(2) instantly estimates biomass quantity in a liquid medium and monitors the development of pathogenic material. It is particularly useful for monitoring the purity of an aquatic environment. It can help detect the risks of bacterial infection in blood and urine. It can also determine the sterility of injectable vaccines, or food products such as milk.
Imagery by bioluminescence: by injecting the luminescent gene into a cell, we can “follow” the development and multiplication of affected cells. This has many important medical applications. For example, it can help doctors discover heart attacks, muscular dystrophy in a newborn, liver disease and it can even follow the development of tumors and cancerous cells.
Light in the cranial cavity
But perhaps its most exciting, and complex, potential application, is mapping out the brain in order to better understand how the brain controls our actions, thoughts, and behaviors. Currently, researchers are able to see what happens in the brain of a mosquito in real time while it’s asleep, awake, or looking at something. This is an enormous scientific breakthrough.
For the human brain, it’s much more complicated: the thickness of the brain tissue means that only a little light is able to get through. The solution? Find red light sources: red light has the largest wavelengths and so is able to move through brain tissue. To find this light, human light chasers are reaching deep into the furthest reaches of the ocean to find species emitting red tones…
While medical applications are currently the most promising applications of bioluminescence, other non-medical projects are underway. For example, Dutch designer Daan Rossegaard studied the possibility of replacing public electric light with bioluminescent trees!
More gimmicky, but no less impressive, the California start-up, “Growing Plants,” offers a luminescent plant, which provides natural lighting without electricity. To date, the project isn’t completely finished, but if you want to be the first to replace your lamps with plants, the website is taking pre-orders!
The magical and largely unexplored world of living light contains thousands of secrets – and with them, potentially thousands of innovations that could truly change and advance humankind.
(1) Lucifer literally means “bearer of light”
(2) For more information about ATP test: https://en.wikipedia.org/wiki/ATP_test