Eight previously unknown invertebrate creatures have been discovered in a cave in central Israel.
The largest is a white shrimp-like crustacean. Another resembles a species of scorpion and is blind.
The cave, near the city of Ramle, contains a lake and was uncovered during drilling at a quarry.
Scientists say it is a unique ecosystem that has been sealed off from the rest of the world for five million years and could contain other ancient lifeforms.
"The uniqueness is of the environmental conditions and of the palaeohistory," said Dr Hanan Dimantman, a biologist at the Hebrew University of Jerusalem.
"The result of this is that the ecosystem is unique. We are sure that the eight species that were found are only the beginning of the story of this ecosystem."
The cave is connected to a lake and a network of passageways that extend for more than a mile (1.6km) and some 400ft (120m) underground.
The ecosystem is thought to date back millions of years to a time when the area was part of the Mediterranean Sea.
The creatures have yet to be given scientific names
Scientists believe the ecosystem has been isolated since then, creating a unique environment in which new species have evolved.
Two of the crustaceans are adapted to seawater and two others live in fresh or brackish water, suggesting they may be descended from ancient sea creatures.
They have lost their eyes over the course of evolution in the gloom of the cave.
All of the species were found alive, except for one species of blind scorpion; but scientists are confident that a complete set of living specimens will be found.
Samples have been sent to experts in Europe and Israel to be named and classified.
Paul Pearce-Kelly, senior curator of invertebrates at London Zoo, UK, said the organisms would give clues to how life could evolve in the absence of sunlight.
"They can give a very good insight into how robust life, and the evolutionary process driving it, can be," he said.