Scientists exploring the world's deepest cave say they've identified a previously unknown species of beetle living in its depths, proof that new discoveries still wait beneath the earth.
The new beetle species, Duvalius abyssimus, was discovered in the Western Caucasus region of Russia in the Krubera cave, which is at least 7,000 feet deep.
Even getting from its entrance to its deepest explored point requires researchers to don diving gear to get through underground chambers flooded with water.
Researchers Ana Sofia Reboleirra of the University of Aveiro in Portugal and Vicente M. Ortuño of the University of Alcalá in Spain, writing in the journal Xootoaxa, described their find.
"We only have two specimens, a male and a female," says Ortuño. "Although they were captured in the world's deepest cave, they were not found at the deepest point."
Cave beetle species are found in underground ecosystems throughout the world and were historically the first species identified by science as being adapted to a subterranean, or hypogean, environment.
Most species of the genus Duvalius have taken up a subterranean lifestyle, the researchers say.
However, D. abyssimus hasn't completely evolved to suit life in total darkness, Ortuño says.
"The new species' characteristics indicate that it is moderately adapted to life underground," he says. "Proof of this is that they still have eyes, which are absent in the highly specialized cave species."
The Krubera cave system, considered by many researchers and scientists as the "Everest of the Caves," is an unusual habitat, with fauna of Asian, European and endemic origins found there.
The entrance to the Krubera cave, which drops deep into Jurassic-Cretaceous limestone, is at 7,350 feet above sea level about 50 miles from the Black Sea.
Vertical sections go down to around 4,500 feet before the cave splits into a number of branches that have been explored to as deep as 7,000 feet.
Although difficult to reach, they offer opportunities for science to push the boundaries of what is known about life deep underground, the researchers say.
"The discovery of the new beetle provides important data on species that co-exist in these almost unknown ecosystems, even more so when they are found in a geographical area that is very difficult to access, such is the case with this cave," Ortuño says.