Researchers exploring the deep ocean have discovered hundreds of species unknown to science, including strange worms, crustaceans and other creatures that live beyond the reach of the sun's rays.
The scientists used cameras, sonar and other equipment on five missions to study life in progressively deeper realms.
The effort to inventory the creatures of abyss was part of the Census of Marine Life, an ambitious 10-year-effort to chart the diversity, range and abundance of life in the oceans. It is an international project, involving 334 scientists from 34 countries, including Canada.
The deep sea is the Earth's largest continuous ecosystem and largest habitat for life, says Bob Carney, a professor of oceanography at Louisiana State University.
It is dark and cold down there, about three degrees Celsius.
Most of the sea floor is mud, says Dr. Carney. But there is so much of it, with so many rare species of small clams, crustaceans and worms that it may have greater biodiversity than the tropics, he says.
Some of the animals feed on chemical or gases that would be toxic to most living creatures. Dr. Carney shot video of a solitary "wildcat" tube worm that leaked crude oil after it was yanked from the bottom of the Gulf of Mexico with a robotic arm.
These tubeworms have a hard body, much like human finger nails, and feeds on hydrogen sulfide, a gas that is produced as petroleum is broken down by bacteria. Except at very low levels, hydrogen sulfide is deadly to most animals.
But this worm was feasting.
"When we pulled the worm up the sticky oil went streaming away. The water was about five degrees so it looked like molasses," says Dr. Carney.
On a voyage to the Mid-Atlantic Ridge earlier this year, researchers taking part in the census found several "Dumbo" octopuses that use large ear-like fins to swim.
One was two metres long, the largest octopus of this kind ever collected. Another may be new to science.
On a trip to the Antarctic, the scientists found a new species of worm that eats the bones of dead whales.
It takes so long for them to grow that many of the species that live in the deep ocean are old. Tube worms, for example, can be 100 to 200 years old, says Dr. Carney.