Deep under the Mediterranean Sea small animals have been discovered that live their entire lives without oxygen and surrounded by 'poisonous' sulphides（硫化物） . Researchers writing in the open access（开架阅览） journal BMC Biology report the existence of multicellular organisms（多细胞生物） (new members of the group Loricifera胸板动物门，兜甲形动物门), 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（重新得到，恢复） sediment（沉淀物） samples from a deep hypersaline（超盐性的） anoxic（缺氧的） 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（需氧的） mitochondria（线粒体） , these animals possess organelles（细胞器） resembling the hydrogenosomes（氢化酶颗粒） found previously in unicellular organisms (protozoans) that inhabit anaerobic environments（缺氧环境，厌氧环境） .

The implications of this finding may reach far beyond the darker parts of the Mediterranean Sea floor, according to Lisa Levin of the Scripps Institution of Oceanography. In one of two commentaries（注释，评论） accompanying this piece of research, she said, "The finding by Danovaro et al. offers the tantalizing（撩人的，逗引性的） promise of metazoan（后生动物的，多细胞动物的） life in other anoxic settings, for example in the subsurface（表面下的，底下的） ocean beneath hydrothermal vents（深海热泉） or subduction zones（隐没带，俯冲带） or in other anoxic basins". In the second commentary Marek Mentel and William Martin, from Comenius and Dusseldorf Universities look at the incidence of anaerobic mitochondria and hydrogenosomes in other organisms and focus on the evolutionary significance of the new findings. "The discovery of metazoan life in a permanently anoxic and sulfidic environment provides a glimpse of what a good part of Earth's past ecology might have been like in 'Canfield oceans', before the rise of deep marine oxygen levels and the appearance of the first large animals in the fossil record roughly 550-600 million years ago".