Scientists have discovered the only known animal to survive without oxygen and it lives in the harsh conditions in the depths of the Mediterranean sea.

Scientists have discovered the only known animals that can live without oxygen.

The creatures, known as metazoa or multicellular animals, were found living in very harsh conditions at the bottom of the Mediterranean Sea.

These new discoveries have not been named yet, although they belong to a group known as Loricifera. They are less than 1mm long and live more than 3km below the surface. They live in areas where the water is very salty and has high concentrations of sulphides, which are toxic to most creatures.

The only things ever to have been found living in environments with no oxygen are things like viruses and bacteria. Some multicellular creatures have been spotted in these places before, but they were thought to have sunk there from water that contained oxygen. These new animals spend their whole lives in these places.

The creatures have specially adapted cells that allow them to survive without oxygen. Scientists now hope to study them further to learn more.

The discovery was reported by a team of researchers in BMC Biology.