A city of brittle stars off the coast of New Zealand, an Antarctic expressway where octopuses ride along in a flow of extra salty water and a carpet of tiny crustaceans on the Gulf of Mexico sea floor are among the wonders discovered by researchers compiling a massive census of marine life.

"We are still making discoveries," but researchers are also busy assembling data already collected into the big picture of life in the oceans, senior scientist Ron O'Dor said.

The fourth update of the census was released ahead of a meeting of hundreds of researchers that began in Valencia, Spain. More than 2,000 scientists from 82 nations are taking part in the project, which is to be completed in 2010.

A discovery that delights O'Dor is that many deep-ocean octopuses share an Antarctic origin. As the Antarctic got colder, ice increased and octopuses were forced into deeper water, he said in a telephone interview.

Salt and oxygen are concentrated in the deeper waters, he said. This dense water then flows out, carrying along the octopuses that have adapted to the new conditions, enabling them to spread to deep waters around the world.

Deep-water octopuses worldwide, he pointed out, lack the ink sack that allows their shallow-water cousins to shoot out a camouflage screen.

A male sea spider carries its eggs on especially adapted appendages under its body. Pic: Reuters

After all, if they live where it is dark, ink is unnecessary, said O'Dor, a Canadian member of the research team.

Patricia Miloslavich, a senior scientist from Venezuela, is pleased with the newly discovered molluscs, from snails to cuttlefish to squids. Once the census is complete, the plan is to publish three books: a popular survey of sea life, a second book with chapters for each working group and a third focusing on biodiversity.

O'Dor also said researchers are working with the online scientific journal PLoS ONE, which is open to anyone and thus would make the results readily available.

Scientists at the sessions were to hear about the discovery of what the researchers call a brittle star city off the coast of New Zealand. The brittle stars, animals with five arms, have colonised the peak of a seamount - an underwater mountain - where the current flows past at about 2.5 miles per hour. The current delivers such an ample food supply that thousands of stars can capture food simply by raising their arms.

Researchers found a carpet of small crustaceans inhabiting the head of the Mississippi Canyon in the Gulf of Mexico. There are as many as 12,000 of these small crustaceans per square yard.

-AP