Strange creatures of the deep found in underwater 'twilight zone'

Thousands of strange ceatures which exist in perpetual darkness miles below the surface of the oceans have been catalogued for the first time by scientists.

Published: 8:00AM GMT 23 Nov 2009

The Census of Marine Life, a major international project surveying the oceans, recorded 5,722 species living at depths greater than 0.62 miles where the sun never shines.

Many inhabited icy cold black realms as deep as three miles where the pressure would crush a human.

In total, 17,650 species were identified living deeper than 200 metres, the ''twilight zone'' where light barely penetrates and photosynthesis ceases to be possible.

Scientists were surprised by the diversity of life in the deepest reaches of the oceans.

Even the mud at the bottom of the ocean abyss was teeming with living things.

Among the bizarre creatures encountered by the researchers were a six foot long cirrate octopod - nicknamed ''Dumbo'' because of the large ear-like fins it uses to swim - discovered more than a mile deep on the Mid-Atlantic Ridge.

Another was a ''wildcat'' tubeworm caught in the act of dining on crude oil in the Gulf of Mexico. When the worm was extracted by a robot arm from the sea bed, oil gushed both from the animal's body and the hole in which it was found.

Also recovered from the Atlantic was an ''indescribable'' catch of multi-coloured invertebrates, including corals, sea cucumbers and sea urchins living a kilometre below the surface.

At more than 1.7 miles down, in the northern Gulf of Mexico, scientists videoed an odd-looking transparent sea cucumber creeping forward on its many tentacles.

Dr Robert Carney, from Louisiana State University in Baton Rouge, US, one of the Census scientists, said: ''Distribution is pretty straightforward for animals in the deep sea. The composition of faunal populations changes with depth, likely a consequence of physiology, ecology and the suitability of sea-floor habitat condition for certain animals.

''Diversity is harder to understand. Although the mud on the deep sea floor appears monotonous and poor in food, that monotonous mud has a maximum of species diversity on the lower continental margin. To survive in the deep, animals must find and exploit meagre or novel resources, and their great diversity in the deep reflects how many ways there are to adapt.''

The vast majority of creatures collected in mud from the abyssal plain were new to science, said the researchers.

Of some 680 specimens of copepods collected from the south-eastern Atlantic, for example, just seven could be identified.

Among the hundreds of species of earthworm-sized macrofauna found at different sites, 50% to 85% were unrecognised.

British expert Dr David Billett, another member of the team from the National Oceanography Centre in Southampton, said: ''The abyssal fauna is so rich in species diversity and so poorly described that collecting a known species is an anomaly. Describing for the first time all the different species in any coffee cup-sized sample of deep sea sediment is a daunting challenge.''

The scientist used a range of high and low-tech hardware including robot submersibles and sea-floor rovers, coring drills, dredges and trawling nets.

The Census, which is also surveying life at shallower depths, is due to complete its work in October 2010.

Dr Chris German, one of the project leaders from Woods Hole Oceanographic Institution in Massachusetts, US, said: ''The deep sea is the Earth's largest continuous ecosystem and largest habitat for life. It is also the least studied.''

http://www.telegraph.co.uk/news/newstopics/howaboutthat/6628299/Strange-creatures-of-the-deep-found-in-underwater-twilight-zone.html