Bioluminescence, in the light of life

Bioluminescence, in the light of life
Bioluminescence, in the light of life

When living things produce their own light, it is called bioluminescence. This phenomenon, very widespread in nature, mainly among marine animals, but also among fireflies or glow worms, appears much earlier than we thought, 540 million years ago, in corals.

This is quite an old blow for bioluminescence: this capacity of living things to light up from the inside, to produce its own light or to host bacteria which do so, thanks to a series of chemical reactions, would have appeared in small corals 540 million years ago. This is the conclusion of the study by researchers from the Natural History Museum of Smithsonian institution in Washington who have just pushed back the date of appearance of this phenomenon by 200,000 years.

Bioluminescence is particularly widespread in the ocean; 70% of marine animals produce their own lights (not to be confused with biofluorescence which only reflects light). But what puzzles scientists is why are there so many different ways to radiate, shine and light up from within?

From lure to attract prey to defense technique

There are more than 1,500 species of bioluminescent fish, which produce light to hunt and find their prey or partners, but also to communicate and even to camouflage themselves. This is the case of the Hawaiian squid which lights up thanks to a luminescent bacteria living in one of its organs, in order to camouflage itself on the surface in the moonlight by erasing its shadow. Most bioluminescent marine animals live at great depths, making it difficult to study them.

Among the most famous, there is the angler fish, the female of which is equipped with a bioluminescent lure responsible for attracting surrounding prey towards her. Other animals close to jellyfish, such as mnemiopsis, are downright dazzling; the latter has a type of photophores inside its body, transparent and gelatinous, which refracts light producing a rainbow of light repelling predators.

There is also the smallest shark in the world – barely 15 cm – the sagre fire-bearer which lives up to its name. Its bioluminescent organs are located all around its genitals, which allows males and females to be seen from very far away, and to attract each other to the light of their respective genitals. Who says better ?

First appeared 540 million years ago

On dry land, bioluminescence also exists. We know glow worms or even fireflies which emit light thanks to oxidation in their abdomen, a chemical reaction due to the famous Latin luciferin. Lucifer which gives light. And there are a thousand and one other ways to shine.

It is this long and tortuous history of bioluminescence that researchers at the Washington museum have traced using a phylogenetic tree which demonstrates that bioluminescence appeared independently and differently more than 94 times in evolution, the very first time there 540 million years ago in a small group of soft corals with very varied shapes, the octocorals (because they have eight tentacles around their mouths). Corals still present on Earth, mainly in the intertropical band.

As for whether it is this bioluminescence which has ensured their extraordinary longevity, and especially for how long given the threats weighing on corals, that is yet another story that science is trying to shed light on. interior.

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