Colonies of tiny animals that have evolved to thrive in the deepest parts of the Pacific Ocean, losing their hard shells in the process, have been discovered.

　　Japanese researchers reported on Thursday that many of the creatures they dredged up are one-celled animals called foraminifera.

　　What surprised the researchers, however, was not just that these animals do not normally live so deep in the ocean but that all their known relatives have hard shells.

　　The little organisms may have slowly adapted to the dark and high pressure found in the trenches 10km under the ocean, the researchers report in Friday's issue of the journal Science.