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A tiny light in the abyss while all around, darkness reigns. Where does the light come from?

There is a good chance that this spot of light is produced by a humpback anglerfish waving its lure in the hope of catching prey or finding a mate.

This phenomenon is called bioluminescence. Let's try to find out more!

What is bioluminescence ?

Bioluminescence is the ability of some living things to produce light.

Some terrestrial species are bioluminescent such as fireflies, worms or fungi.

In the ocean, many organisms are also bioluminescent, from animal plankton at the surface to organisms in the deep sea, where more than 90% are bioluminescent.

A squid living on the surface produces a cloud of ink in the face of danger, whereas a squid living in the abyss is able to produce a cloud of light. It is the same technique but using different resources!

Producing light: a chemical reaction

To produce this light, a chemical reaction is needed between luciferin, a molecule in which the oxidation caused by luciferase, an enzyme, produces light.

For the chemical reaction to take place, a catalyst is needed, produced by a living being: this catalyst is ATP.

Even though there are a multitude of luciferins and luciferases, each combination is unique and is not interchangeable.

At Nausicaá, splitfin flashlightfish can be seen in the "Journey on the High Seas" exhibition.

Bioluminescence, phosphorescence or fluorescence?

Bioluminescence, phosphorescence or fluorescence are three phenomena that produce light, but have different origins:

  • Bioluminescence is the result of a chemical reaction.
  • Phosphorescence is the ability of certain bodies to emit light after receiving it.
  • Fluorescence is the ability of some organisms to immediately return light after receiving it. Some corals are capable of fluorescence; proteins in coral tissue absorb blue light and reflect green light.

Who is bioluminescent? And why are they so?

What is the purpose of this bioluminescence phenomenon? Primarily for the survival of the species!

To defend themselves from predators

  • The deep-sea shrimp Acanthephyra purpurea can "vomit" a bioluminescent jet on its predators, a bit like octopus and their jet of ink. An effective technique to avoid being eaten!
  • Ostracods, which are small crustaceans, produce a bluish light whenever they are buffeted by the waves or feel threatened. Their presence has made the beaches of the Maldives famous. They are nicknamed Blue Sand.

During the Second World War, Japanese officers were able to read their documents in the dark thanks to cypridina powder (ostracodes), which remains bioluminescent  even when dried.

The Atolla wyvillei jellyfish is a deep-sea jellyfish that produces flashes of light when attacked. This reaction attracts other predators that rid the jellyfish of its attackers.

This ability to attract animals from the depths using flashes of light was copied by Edith Widder, a marine biologist. Her E-jelly camera was used to attract the attention of a giant squid in order to film it in its natural environment in the depths of the ocean. A first of its kind!


The light lure of the humpback anglerfish is a pouch of skin called an esca, filled with luminescent bacteria, which is found at the end of a long spine, a modification of the first spine of its dorsal fin. In other fish of the same family of Lophiformes, the light organ is located on the palate, inside the upper jaw. The fish just has to wait calmly for prey to approach this lure and then it closes its jaws and eats at its leisure.


Fireflies use the light signal to find each other in order to reproduce. In the ocean, the plainfin midshipman Porichthys notatus builds a nest under rocks during the breeding season. It emits a sound to attract a female. If the female is ready to mate, it glows. As the male approaches, it flashes and turns luminescent pink.

What applications can be derived from bioluminescence?

Apart from the fact that observing bioluminescence has enabled us to gain a better understanding of certain species, the phenomenon is of interest to us for its applications in our day-to-day lives.

The medical field

Researchers have been able to use bioluminescent bacteria to precisely locate in 3D a tumour in a mouse. This research could improve medical imaging and thus enable early detection of tumours by accurately estimating their size and shape.

Aequorea, a luminescent jellyfish, contains a protein, aequorin, which can be used as a biological marker in medical research.

Water treatment

ATP-metry (ATP measurement) has been used for a long time in the food industry, in swimming pools and in water systems.

ATP, or Adenosine TriPhosphate, is a molecule found in all living organisms. Therefore, the level of ATP on a surface must correspond to the hygiene standards in force. It turns out that in the presence of the luciferin/luciferase pair and a catalyst, this molecule produces light. So all it takes is a light meter to measure the level: the more intense the light, the more ATP and the greater the risk of bacterial growth in the water.

Natural lighting

Glowee is a French environmental biotechnology startup with a mission to use bioluminescence to reduce the environmental impact of light in cities.

By developing a biological light system that uses the natural bioluminescent properties of marine organisms, Glowee is offering a sustainable alternative to artificial light and a new way of producing and consuming light.


Le monde lumineux des océans by Catherine Vadon………