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Many Octopuses Share Antarctic Ancestors, Research Finds

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Megaleledone setebos, a shallow-water Antarctic octopus, is the closest living relative to the ancestor of deep-sea octopuses. 

A large proportion of deep sea octopus species worldwide evolved from common ancestor species that still exist in the Southern Ocean, Census of Marine Life (CoML) scientists report today.

“Octopuses started migrating to new ocean basins more than 30 million years ago when, as Antarctica cooled and a large ice sheet grew, nature created a ‘thermohaline expressway,’ a northbound flow of tasty frigid water with high salt and oxygen content,” scientists said as part of a report that will be released officially at the World Conference on Marine Biodiversity, in Valencia, Spain.

octopus-2.jpgJuvenile representatives of the Antarctic and deep-sea genera of octopuses. Clockwise from top left , (1) Pareledone charcoti, a shallow-water species from the Antarctica Peninsula, (2) Thaumeledone gunteri, a deep-water species endemic to South Georgia, (3) Adelieledone polymoprha, a species endemic to the western Antarctic, (4) Megaleledone setebos, a shallow-water circum-Antarctic species endemic to the Southern Ocean.

Photo credit: I. Everson (T. gunteri), M. Rauschert (M. setebos), L. Allcock (P. charcoti, A. polymorpha)

Isolated in their new habitat conditions, many different species of octopuses evolved; some octopuses, for example, lost their defensive ink sacs which became “pointless at perpetually dark depths,” CoML researchers said.

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The cruise tracks show CoML scientific voyages to the Southern Ocean during the International Polar Year.

Map courtesy CoML

The finding about octopuses is to be reported by CoML today in the journal Cladistics. It is based on molecular research made possible by intensive sampling during CoML’s International Polar Year expeditions.

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Other highlights announced in CoML’s report:

• Scientists discovered both a “White Shark Café” and a “sturgeon playground” in the Pacific. Other CoML researchers explored life on a “new continent” in the mid-Atlantic, in oceanic canyons, around Earth’s deepest hot vents, and in the world’s coldest, saltiest seawater.

• Deep sea explorers discovered new forms of life, including behemoth bacteria, colossal sea stars, astonishing Antarctic amphipods and a mammoth mollusk, and found familiar species in many new places.

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Experts also estimate that, beyond the 16,000 marine fish species already known to science, another 4,000 await discovery, many of them in the tropics.

• Researchers found a sea floor carpet of bugs and a city of brittle stars, and documented bluefin tuna abundance in the early 1900s by scouring fishery reports, fishing magazines and other records.

The Census of Marine Life is a collaboration of some 2,000 scientists from 82 nations. The report released this week details major progress towards the first ever marine life

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census, for release in October, 2010.

 ”The release of the first Census in 2010 will be a milestone in science,” says Ian Poiner, chairperson of the Census’s International Scientific Steering Committee and Chief Executive Officer of the Australian Institute of Marine Science. “After 10 years of new global research and information assembly by thousands of experts the world over, it will synthesize what humankind knows about the oceans, what we don’t know, and what we may never know — a scientific achievement of historic proportions,” Poiner  said.

“Dedication and cooperation are enabling the largest, most complex program ever undertaken in marine biology to meet its schedule and reach its goals. When the program began, such progress seemed improbable to many observers.”

In 2010, the first global Census will relate:

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• Distribution of animals in the ocean and their changing ranges;

• Diversity as the total number of species in the ocean (known and unknown);

• Abundance of major species groups and how they have changed over time;

With regard to distribution, the Census will offer:

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• Range maps for known marine species;

• Major global traffic patterns of top marine species;

• Global maps of species richness, showing hotspots and the extent of biodiversity in the oceans

With regard to diversity, the Census will offer:

• A complete list of named marine species, likely to range between 230,000-250,000, as well as

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fresh estimates of species yet to be discovered;

• Web pages for the great majority of the named species, compiled in cooperation with the Encyclopedia of Life;

• DNA identifiers (“barcodes”) for many species.

With regard to abundance, the Census will offer:

• New estimates of biomass at various

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levels in the food chain and for selected species;

• Estimates of changes in the relative frequency of small versus large animals;

• Estimates of abundance that has been or might be lost soon.