A new study has cast doubt on the claim that crabs 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 continental 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 other fauna in the region. But an extensive study of all known crab 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 marine 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 susceptible 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 60S). Much of Antarctica is covered with ice restricting access to areas where fossils may be found. This means there is a great deal of uncertainty 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 previously published sources as well as the extensive fossil collection at BAS' offices in Cambridge. All published data for living specimens were examined as well as records from unpublished fisheries' and scientific reports.
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|Contact: Paul Seagrove|
British Antarctic Survey