Deep-Sea Purple Sock Mystery Solved

The mystery of a deep-sea creature that resembles a discarded purple sock has been solved, scientists report in the journal Nature.

The animal, called Xenoturbella, was first described in 1949. But it is so bizarre that for 60 years researchers could not work out what it was - or where it fitted into the family tree.

But the discovery of four new species in the Pacific has enabled scientists to conclude that this animal belongs to one of the earliest branches of life.

Lead researcher Prof Greg Rouse, from the Scripps Institution of Oceanography in the US, said: "Our nickname for them was purple socks.

"So if you think of a sock that you have taken off and thrown on the floor - they literally look like that. "Or a deflated balloon."

The ocean oddity has no eyes, no brain and no gut. Just a small gaping mouth from which food goes in - and then waste comes out.

Only one species was known, and it left scientists scratching their heads.

Early genetic tests mistakenly placed the marine "sock" as a mollusc. "But it turned out they had sequenced the DNA of what it eats," explained Prof Rouse.