A new study has cast doubt on the claim that crabs² may have disappeared from Antarctica only to return due to warming seas. The theory surfaced two years ago following the discovery of a major colony of King crabs (Lithodidae) in the Palmer Deep, a basin in the continental³ shelf off the Antarctic Peninsula. It was thought the species may have left the continent between 40 and 15 million years ago and was returning as seawater temperatures rose. Fears were expressed that its reintroduction would decimate（十中抽一） other fauna⁴（动物群） in the region. But an extensive study of all known crab¹ records by a team of scientists at British Antarctic Survey (BAS) has led it to conclude the crabs may have been there all along rather than moving in from a different area.

 

Writing in the online journal PLOS ONE the team, led by marine⁵ biologist, Huw Griffiths, claims the "invasion" hypothesis is fundamentally flawed because it relied upon poor fossil records relating to a completely different group of crabs and that sampling of the extant species is far too limited to draw any firm conclusions.

 

The fossils of deep water crabs are hard to come by because they are susceptible⁶ to decay soon after they die. There is no Antarctic fossil record for King crabs with only two such records existing, neither of which originate from Antarctic waters (south of 60°S). Much of Antarctica is covered with ice restricting access to areas where fossils may be found. This means there is a great deal of uncertainty⁷ surrounding the history of crab populations in the continent.

 

The team assembled a database of more than sixteen thousand records of living and fossil crabs to assess the extent of their populations. Fossil data were compiled from all previously⁸ published sources as well as the extensive fossil collection at BAS' offices in Cambridge. All published data for living specimens⁹ were examined as well as records from unpublished fisheries' and scientific reports.

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