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Arctic, Antarctic? All the same for some

AT Least 235 types of cold-loving creatures thrive in both Arctic and Antarctic seas, puzzling scientists about how they got to both ends of the Earth, according to preliminary findings of a study announced yesterday.

The warm tropics have been seen as a barrier keeping polar bears in the Arctic separate from penguins in the Antarctic. Only a few creatures have been known in both polar regions, such as long-migrating grey whales.

"At least 235 species live in both polar seas despite an 11,000-kilometer distance in between," according to the Census of Marine Life, a decade-long international project to map the world's oceans whose final results are due in October 2010.

Species living at both poles include cold-water worms, crustaceans, sea cucumbers and snail-like pteropods. They make up 2 percent of the 7,500 Antarctic and 5,500 Arctic animals known to date, out of a global total estimated at up to 250,000.

"The Arctic and Antarctic are much more alike than we thought," Ron O'Dor, senior scientist of the census, told Reuters. Genetic studies were being carried out to confirm that the 235 species were identical.

The findings, along with a discovery that the frigid seas teem with life, raise questions about where common polar species "originated and how they wound up at both ends of the Earth," the census said in a statement.

Among theories were that larvae of some species could be swept northward from Antarctica by cold currents along the deep floor of the Atlantic Ocean - away from warm surface waters in the tropics that would kill them.

"Animals can be dispersed over such long distances at the deep sea floor," said Julian Gutt of the Alfred Wegener Institute in Germany, a senior member of the census. "The most likely direction is from the Antarctic."

But he said he knew of no finds of cold-loving species in the depths near the equator to back up the theory.

Ice Ages may have helped species disperse. During Ice Ages Antarctica's ice smothered surrounding seas and caused new northbound currents that could have carried species such as sea spiders or crustaceans known as isopods. Genetic studies have traced many types of octopus to an Antarctic ancestor.


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