Marseilles (AFP)

A new species of crustacean living in darkness has just been identified near Marseille.

Similar to a tiny shrimp, it is not and belongs to a category that is still poorly understood, according to one of the researchers who discovered it.

Measuring barely two to three millimeters, the crustacean inhabits the brackish waters of an underground river in Calanques National Park, about a kilometer from the Mediterranean coast.

Called "Tethysbaena ledoyeri", it evolves in a hostile, totally dark environment, between limestone walls covered with clayey silt where no plants grow.

Without eyes, the crustacean would move in the dark thanks to a very fine sense of smell and touch, detailed to AFP Pierre Chevaldonné, research director at the National Center for Scientific Research (CNRS) in biology and ecology marine, at the origin of this discovery.

The animal feeds on bacteria and can "practically fast" for long months, he added.

Underground water is little explored by scientists, because it is difficult to access, which explains the late identification of the crustacean, twenty years after the first observations made in the 1990s by speleologists.

"Until 2003, the single specimen collected was too damaged to describe the species," explains Pierre Chevaldonné, whose explorations began at that time.

Twenty years later, in 2019, he took the sample that would allow him to formalize the discovery, with his Dutch counterpart, the biologist HP Wagner, a specialist in this group of species.

The crustacean was finally described in September 2020 in the scientific journal Crustaceana.

Located in an area of ​​narrow rocky coves bathed by the Mediterranean, the Calanques National Park was delighted with this discovery on its territory.

"The park is a very scrutinized and surveyed environment. Yet we continue to be surprised."

Especially since the species could be endemic, according to the researcher.

The discovery of this crustacean completes a group of species still poorly understood by scientists.

This is the taxonomic order of Thermosbaenaceae, evolving in groundwater, difficult to access.

The group currently only has 37 different species in the world, none of which have been identified so far in France.

"It's as if I told you that we discovered for the first time a species of bat in France", notes Pierre Chevaldonné.

This discovery could also lead to others.

Pierre Chevaldonné is currently wondering about a sea flea, which could be a predator of the crustacean.

© 2020 AFP