Changing ocean temperatures may allow giant, voracious, predatory crabs to enter the unique continental-shelf ecosystems of Antarctica.

Research by scientists at the National Oceanography Centre in Southampton in the United Kingdom found that even small increases in water temperature due to global warming could bring king crabs into new areas.

King crabs are a popular food source. But historically they haven't been able to live in the high-Antarctic continental shelves, so the species that currently live there have not evolved to cope with them.

The research is in the October issue of the journal Polar Biology.

The crabs are cold blooded and their larvae can't mature in water temperatures below around 32.9 degrees Fahrenheit. This "thermal barrier" has kept them out of the Southern Ocean, author Sven Thatje, an evolutionary ecologist at the University of Southampton's School of Ocean and Earth Science, said in a release.

The researchers found that even small increases in water temperature due to global warming could lead to king crabs moving into new areas. "Rapidly increasing water temperatures observed along the West Antarctic Peninsula could allow king crabs to spread from the slope of the peninsula to the continental shelf itself," co-author Sally Hall said in the release.

The researchers studied the distribution of seventeen species of king in the Southern Ocean. They found that the coldest waters the crabs have been found are between 32.72 and 32.9°F in the Ross Sea. Only two species live in waters south of 60 degrees South.

The arrival of this species, which crushes and then eats its prey, could cause a major shift in the populations that now live in the high-Antarctic continental shelves. "The worry is that the sudden appearance of a new predator with few competitors could threaten isolated shelf communities such as those of the Bellingshausen Sea on the west side of the Antarctic Peninsula," Hall said.

By Elizabeth Weise