Predatory crabs, sharks and rays have begun extending their domain towards the Antarctic continental shelf in the Southern Ocean because of increasing sea temperatures, The Times of London reported.

Cold temperatures previously kept predators out of the region that has allowed unusual sea creatures including sea snails, large sea spiders and isopod crustaceans to safely exist in the ocean, the report said.

It is reported that because these animals have never had to fight off aggressive predators, they are unprepared for the possible invasion of bony fish and crabs.

"The crabs are on the doorstep. They are sitting in deep water, and only a couple of hundred bathymetric meters now separate them from the slightly cooler shallow water in the Antarctic shelf environment," Sven Thatje, of the National Oceanography Centre at Southampton, England, said at a conference in Boston.