King crabs may be poised to conquer the Antarctic as a result of global warming, scientists have warned.

The creatures could soon be disturbing delicately balanced Antarctic marine ecosystems, where they have not played a role in tens of millions of years, according to a new study.

Rising temperatures of the ocean west of the Antarctic peninsula should make an invasion of king crabs possible within the next several decades, say the researchers.

Lead author Professor Richard Aronson, from Florida Institute of Technology in the US, said: "Because other creatures on the continental shelf have evolved without shell-crushing predators, if the crabs moved in they could radically restructure the ecosystem."

The scientists used an underwater camera sled to film a reproductive population of the crabs for the first time on the continental slope off Marguerite Bay, on the western Antarctic peninsular. That location is only a few hundred metres deeper than the continental shelf where the delicate ecosystem flourishes.

US co-author Dr James McClintock, from the University of Alabama at Birmingham, said: "The only way to test the hypothesis that the crabs are expanding their depth-range is to track their movements through long-term monitoring."

The research is published in the journal Proceedings of the National Academy of Sciences.

Despite our image above, the local penguin population shouldn't be alarmed - the shells of the largest king crabs grow to only about 11 inches, though they can boast a six-foot leg span.