Species name: Not yet assigned, but of the phylum Loricifera, genus Spinoloricus
Habitat: Deep sediments lacking oxygen in the L'Atalante basin of the Mediterranean Sea south of Greece - and who knows where else
This tiny creature may not look spectacular, but it is one of the most remarkable ever discovered: the first that can survive and reproduce entirely without oxygen.
As well as proving that animals that don't have to breathe oxygen have already evolved on Earth, it bolsters claims that complex animals can evolve on other planets even if there's no oxygen. Some have speculated, for example, that sulphur-rich areas of Mars might support life.
On Earth, bacteria, viruses and ancient archaea that survive without oxygen are well-known, but they are simple, single-celled organisms. What marks out the new animal is that it has millions of cells and functions independently.
Roberto Danovaro of the Polytechnic University of Marche, Ancona, Italy, led the team that discovered the creature, plus two others that live an oxygen-free existence, in sediments buried deep beneath the Mediterranean Sea. They've identified the creatures as loriciferans, tiny sediment-dwelling creatures so named from Greek because their abdomens resemble girdles.
Assigned the genus Spinoloricus, the animal is less than a millimetre long. The other two new loriciferan species Danovaro found resemble water fleas, one given the genus name Rugiloricus and the other Pliciloricus. Some specimens contained an unfertilised egg.
The beasts live in conditions that would kill every other known animal. As well as lacking oxygen, the sediments are choked with salt and swamped with hydrogen sulphide gas.
None of the animals has mitochondria, the "power stations" that generate energy from oxygen in the cells of all oxygen-using organisms. Instead, they rely on structures called hydrogenosomes, which generate energy from molecules other than oxygen, including hydrogen sulphide.
Hydrogenosomes are well known in protozoa that live in oxygen-free environments, but the three new creatures are the first animals to be found that rely completely on them. One possibility is that the loriciferans acquired the hydrogenosomes from protozoa.
Detailed light microscopy images reveal that its abdomen "girdle" consists of eight plates connected to form a cone, tipped with a honeycomb structure of unknown function.
Lisa Levin of the Scripps Institution of Oceanography in La Jolla, California, says that the discoveries offer the tantalising promise that animal life will be found in other environments devoid of oxygen, including beyond our planet. Perhaps, she speculates, there are animals on other planets with atmospheres different from our own. More encouragement could come from further exploration of our own "inner space", the deep ocean.
Journal reference: BMC Biology, DOI: 10.1186/1741-7007-8-3
From here. This is the first time we've found a multicellular organism that can suvive in anaerobic conditions.