Washington, Nov 23 : An ongoing census of deep-sea animals has revealed an astonishing abundance, diversity and distribution of species. Deep-towed cameras, sonar and other vanguard technologies have identified some 17,650 species thriving in the darkest deep, a bewildering collection ranging from crabs to shrimp to worms.

These creatures somehow eke out an existence in a frigid black zone five km below the turbulent waves, beyond the pale of sunlight.

Most have adapted to diets based on meagre droppings from the sunlit layer above, others to diets of bacteria that break down oil, sulphur and methane, the sunken bones of dead whales and other implausible foods.

Five of the Census' 14 field projects plumb the ocean beyond light, each dedicated to the study of life in progressively deeper realms.

They range from the continental margins to the spine-like ridge running down the mid-Atlantic, submerged mountains rising from the seafloor, the muddy floor of ocean plains and the vents, seeps, whale falls and chemically-driven ecosystems found on the margins of mid-ocean ridges.

Edward Vanden Berghe, who manages Ocean Bio-geographic Information System (OBIS), the Census' inventory of marine life observations, notes that the number of records in the database falls off dramatically at deeper depths -- a function of the dearth of sampling done in the deep sea, says an OBIS release.

Scientists working on the deep-sea census number 344 and span 34 nations.

By the time the 10-year census concludes in October 2010, the five deep-sea projects will have collectively fielded more than 210 expeditions, a scientific collaboration among Russia, Brazil, South Africa and Uruguay.

Each voyage is hugely expensive and challenged by often extreme ocean conditions and requirements that have kept such remotest reaches impenetrable until recently.(IANS)