The invisible teeth of the dragon of the abyss


Living paradox, this fish of the depths hides his formidable jaw by opening up his huge mouth.

Posted today at 17:00 Time to Reading 2 min.

A dragon fish caught off California.
A dragon fish caught off California. AUDREY VELASCO

"Zoology". It is a world apart, a hostile universe, a poorly known environment, where all our landmarks disappear. Here are unbearable pressures for most living creatures, freezing temperatures, an eternal night. Living therefore imposes a special degree of adaptation for species. And an exceptional lot of surprises for scientists. Not long ago, we told the extraordinary vision of the fish of the deep sea, able to detect the imperceptible … in color. But in the arms race developed under the sea, if it is important to see, hiding itself is just as necessary. To avoid predators, or to reach prey.

The dragon fish is certainly one of the scariest beings there is. Viewed from a distance, its approximately 15 cm to 25 cm long can leave indifferent. But his ripples quickly turn him into a snake. And, if the idea has just opened his mouth, the astonishment gives way to dread: the black fish disappears behind a huge jaw covered teeth all the more impressive as they are transparent. The creators of Alien were not deceived, who have decked one of their monsters of such a denture.

An international team details in the journal Matter, the secrets of this formidable weapon. A curious mixture of weakness and strength. In order to open wide the mouth, the voracious animal has developed a jaw called "soft". But it compensates for the lack of power by a particularly sharp tooth. Five times more penetrating than that of the famous piranha, according to measurements made by scientists, this series of daggers enters the flesh of its prey as in butter. Still, we must approach them. Or make them come to you. For that, Aristostomias scintillans has a kind of photoluminescent beard that attracts fish such as light moths, all the more easily as the teeth are invisible.

Tiny nanocrystals

It is on this last aspect that Marc Meyers and his colleagues at the University of California at San Diego (UCSD) have just made a breakthrough. The Brazilian scientist has been tracking for twenty years the improbable materials of nature, fish scales, beaks and feathers of birds, bones of all kinds. "I had heard about these transparent fangs, I wanted to understand", he says. With the oceanographer Dimitri Deheyn (Scripps Institution of Oceanography), he has collected a few specimens, abundant off California, as far as we go down below 500 meters. The team then moved closer to Eduard Arzt, director of the Institute for New Materials in Saarbrücken, Germany, to take advantage of the center's outstanding imaging capabilities.

"We were hoping to discover a really new material, says the researcher. But no: enamel and dentin are like home made of collagen and hydroxyapatite. On the other hand, we detected tiny nanocrystals, about 20 nanometers, which proved to be transparent. " By reducing both the light diffusion and the ability of the teeth to reflect light, especially in the wavelength emitted by the luminescent beard, the impurities ensure the invisibility of the teeth on the black background of the mouth. "With the same starting materials, nature has created completely different properties: it's fascinating"enthuses the Brazilian scientist.

The team now plans to measure the other features of these teeth, their rigidity and their resistance to fracture, among others. Marc Meyers especially hopes to synthesize "A new class of bio-inspired, resistant and transparent materials". A dragon dream.

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