By Fiona Hodge

Scientists have recently discovered animals able to live their entire lives in the absence of oxygen. Oxygen was thought to be a necessity for multicellular life, so this discovery completely changes where we expect complex life to occur. It suggests we should look more closely in the deep sea, parts of which lack oxygen, and perhaps even beyond our own planet.

The multicellular animals discovered were three new species of loriciferans. Loriciferans are a tiny animal, a quarter of a millimetre long, that spend their entire lives tightly attached to marine sediments. They live in the sediments in the Mediterranean Sea, at a depth of three kilometres, under a forty metre brine layer which blocks oxygen. The sediments are not only oxygen lacking, or anoxic, but also contain high hydrogen sulphide concentrations.

The loriciferans found have unique adaptations that allow them to live without oxygen. Most interestingly these loriciferans have a completely different metabolism system to most other multicellular organisms.

Loricifera; stained with Rose

All organisms need to convert the energy gained from their food into energy that can be used internally. This is like having to convert New Zealand dollars into Australian for your money to work in Sydney. Most multicellular organisms require oxygen to do this (using mitochondria). The anoxic loriciferans use an alternative ‘bureau de change’ system which doesn’t require oxygen (hydrogenosomes). Their system has never before been found in a multicellular organism.

The loriciferans’ adaptations and ability to live in such an inhospitable environment are truly impressive. They gives us a tempting insight into what life might have looked like in the distant past, when oxygen was scarce, and what it might look like in other oxygen-less places…