A species of sea anemone found on the underside of Antarctica's ice sheets is the only marine animal known to live embedded in ice, U.S. researchers say.

No one is sure how the anemones, which burrow upward into the ice with only their tentacles dangling into the water, are able to survive, scientists at the University of Nebraska-Lincoln and Ohio State University said.

Researchers using a camera attached to a remote-controlled drill to explore the underside of the Ross Ice Shelf in a geological study were surprised to discover large numbers of the white anemones, Edwardsiella andrillae, hanging from the underside of the sea ice.

"I would never have guessed that they live embedded in the ice because there is nothing different about their anatomy," Ohio State researcher Marymegan Daly, who analyzed samples, told NewScientist.com

Some anemone species burrow into surfaces by digging with their tentacles, but ice should be too hard, she said.

The newly discovered species may secrete chemicals to dissolve the ice, she said.

It is unclear how they survive without freezing and how they reproduce, the researchers said in a report of the study published in the journal PLoS ONE.