- Meet the Xenophyophores: Scientists have announced the discovery of a hitherto unknown, large single-celled organism living about 6.6 miles beneath the ocean’s surface. The organisms, called xenophyophores, were discovered in the Mariana Trench, the deepest place known in the ocean floor. They aren’t kidding about the “large,” either — a single cell can exceed four inches, which kind of blows our minds, honestly. Research suggests the xenophyophores are resistant to heavy metal toxicity, as by trapping water particles they concentrate high levels of mercury, uranium and lead, with no apparent detriment to the their health. source