June 3, 2011

It Came From The Deep!

Researchers unearth deepest-living animal ever found

A team of researchers has discovered two species of a worm, living deeper than any other known animal on the planet, where experts previously believed no animal except single-cell bacteria could survive.

The discovery of Halicephalobus mephisto, a new species of worm, and a previously known species, Plectus aquatilis, were discovered 2.2 miles below the surface in a South African gold mine thriving in sultry 118-degree Fahrenheit water that seeped between the cracks.

Writing in the journal Nature, the team of researchers said this is the deepest-living "multi-cellular" organism known to science. Until now, only single-celled bacteria and fungi have been recovered from far below Earth's crust. The lack of oxygen is thought to keep most larger organisms from attempting to make their home there.

Earth's vast subterranean world is largely inaccessible to researchers, making it difficult to find new species of multi-cellular organisms if any exist. However, in areas where they can gain access, they are always looking.

Taking advantage of two sites -- the Beatrix and the Driefontein gold mines in South Africa -- the international team of researchers placed filters over the mines' boreholes through which thousands of liters of groundwater pour through.

Scientists expected only to find bacteria, but the worms were an amazing surprise. "It scared the life out of me when I first saw them moving," said geo-microbiologist Dr Tullis Onstott of Princeton University in New Jersey, US. "They look like black little swirly things."

The worms seem fully capable of thriving in the very low levels of oxygen -- at 1 percent the levels found in most oceans, explained Onstott.

Is it possible the worms were carried in with them? The water in which the worms were found is between 3,000 and 10,000 years old, and so it is unlikely that the researchers brought the worms with them into the mines, Dr Onstott noted.

The scientists believe that the animals originally came from the surface but got washed down into the cracks in the Earth's crust by ancient rainwater.

Dr Gaeten Borgonie, a member of the research team, told BBC News that he thinks the animals look a lot like the tiny worms that live on rotting fruit and soil at the surface, and probably descended from them.

Worms at the surface experience greater extremes in temperatures and can survive being frozen and thawed, dehydrated and re-hydrated, he explained. Borgonie believes that the worms already have some of the "attributes necessary" to survive at the great depths. So it wasn't a surprise to him that the first multi-cellular organism found in the Earth's great depths was a worm.

The authors of the study expect to find more multi-cellular animals living far beneath the planet's surface, and are planning further descents to search for more creatures.


Image Caption: Halicephalobus mephisto. Credit: Ghent University


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