Loricifera [drawing, NASA]
Meet the loricifera. It’s not a neighbor; living 10,000 feet down in the muck at the bottom of the Mediterranean Sea. It’s not a relative, not even close, in fact, it doesn’t use oxygen. That in itself is not unusual for bacteria or viruses, but loricifera is neither bacteria nor virus. It is a significantly large multicellular creature – 1.016 mm (4/100 inch) in length. So far, this is the only animal of this size and complexity that does not have mitochondria (busy little workshops in the cell, probably remnants of a fusion with bacteria eons ago). Mitochondria use oxygen, but loricifera have something like hydrogenosome organelles, perhaps an equivalent to mitochondria; and in their complex enzyme processing, they use hydrogen instead of oxygen.
Loricifera, that’s the phylum name, other nomenclature will follow as the new beastie is studied, are little more than digestive system and an outer shell (the lorica). Other species of loricifera have been found before; but this is the first one that does not need to migrate to areas with oxygen. It stays at the anoxic bottom permanently.
While the researchers had located multi-celled animals in other anoxic environments, this is the first discovery of oxygen-independent, mitochondria-less metazoa—multi-celled animals—living in this particular basin. And these are the first that researchers believe are permanent residents of an oxygen-starved environment. In a Nature article today, [Roberto] Danovaro [Polytechnic University of Marche in Ancona, Italy] described the exploration of biodiversity in this anoxic environment like “going to the Moon to collect rocks.”
[Source: European Space Administration]
The reference to the Moon isn’t accidental. Notice too that this article comes from the European Space Agency (ESA) and the picture above from the U.S. space agency, NASA. The presence of multicellular complex life at depths without sunlight and with little or no oxygen, make it all the more likely that other planets with oceans or persistent water pockets could also harbor larger forms of life – not just single cell or few-cell creatures. Current candidates are the moons Enceladus (Saturn), Europa (Jupiter), and the planet Mars.
Long before that possibility is explored, scientists on Earth will be studying loricifera intensely – it’s an anomaly and anomalies often teach us more than the more common and ‘normal.’