For the first time, scientists have claimed to have discovered animals that live without oxygen deep under the Mediterranean Sea. These creatures called 'loriciferans', which measure less than one millimetre in length and somewhat resemble jellyfish sprouting from a conical shell, were found by team of Italian researchers from 10,000-feet deep hyper-salty basins in the Mediterranean Sea. Though scientist in the past have found a wide variety of single-celled organisms that live anaerobically, or without oxygen, they never had an encounter with live multi-cellular or metazoan animal living without oxygen in deep seas. According to researchers at the Polytechnic University of Marche in Ancona, Italy, the new findings could shed light on what life might have looked like before the rise of oxygen levels in the deep ocean and the appearance of the first large animals in the fossil record roughly 550 million to 600 million years ago, LiveScience reported.
The deep Mediterranean basins are completely anoxic, or oxygen-free, and loaded with toxic levels of sulfides. In these extremes, the researchers were only expecting to see viruses, bacteria and other microbes. Roberto Danovaro, who led the team that conducted three expeditions off the south coast of Greece looking for signs of life in samples of mud from deep hyper-salty basins, said they have earlier found bodies of multi-cellular animals in these sediments. But they "were thought to have sunk there from upper, oxygenated, waters", said Danovaro. Instead, "our results indicate that the animals we recovered were alive," the scientist said, adding that "some, in fact, also contained eggs". The scientist explained that electron microscopy revealed the three new species of loriciferans found from the basins lack mitochondria -- the energy-making organelles or components in our cells that allow us to generate energy from oxygen among other functions. "Instead, they possess large numbers of organelles resembling hydrogenosomes -- anaerobic forms of mitochondria -- that were previously seen in single-celled organisms inhabiting no-oxygen environments."
According to biological oceanographer Lisa Levin of the Scripps Institution of Oceanography in San Diego, the implications of this discovery might also reach far beyond the Mediterranean Sea. The new finding "offers the tantalising promise of metazoan life in other anoxic settings -- for example, in the subsurface ocean beneath hydrothermal vents, or subduction zones, or in other anoxic basins," Levin said. Danovaro and his team reported their findings online in journal BMC Biology.