Deep under the Mediterranean Sea small animals have been discovered that live their entire lives without oxygen and surrounded by ‘poisonous’ sulphides. Researchers writing in the open access journal BMC Biology report the existence of multicellular organisms (new members of the group Loricifera), showing that they are alive, metabolically active, and apparently reproducing in spite of a complete absence of oxygen.
Roberto Danovaro, from the Polytechnic University of Marche, Ancona, Italy, worked with a team of researchers to retrieve sediment samples from a deep hypersaline anoxic basin (DHABs) of the Mediterranean Sea and studied them for signs of life. “These extreme environments”, said Danovaro, “have been thought to be exclusively inhabited by viruses, Bacteria and Archaea. The bodies of multicellular animals have previously been discovered, but were thought to have sunk there from upper, oxygenated, waters. Our results indicate that the animals we recovered were alive. Some, in fact, also contained eggs”. Electronmicroscopy shows that instead of aerobic mitochondria, these animals possess organelles resembling the hydrogenosomes found previously in unicellular organisms (protozoans) that inhabit anaerobic environments.