February 24, 2012
Scientists Discover World’s Deepest-Living Creature
Over a mile beneath the Earth´s surface in the pitch black depths of the world´s deepest cave, a team of Spanish and Portuguese scientists have discovered several new species of animals, one of which they are describing as the deepest terrestrial animal known to man.
The tiny arthropod, already dubbed with the Latin name Plutomurus ortobalaganensis, is one of four newly discovered species of wingless arthropods known to entomologists as springtails. Part of a subclass of arthropods known as Collembola, the little animals are usually less than 6 mm in length and often found in total darkness, obtaining nutrients from decaying organic matter.The fossil record of springtails reaches back some 400 million years to the Early Devonian period, making them one of the most ancient species of extant arthropods on the planet.
The creatures were discovered during the Ibero-Russian CaveX team expedition to the world´s deepest known cave Krubera-Voronja in the mountains of Western Caucasus. Located on the Black Sea in the disputed territory of Abkhazia, the abyss-like cave reaches down some 7,188 feet (1.4 miles) below the surface of the Earth.
“The CaveX team has been exploring this cave for more than 10 years, hard and dangerous work in a remote area inside the mountains,” explained lead researcher Sofia Reboleira, a specialist in cave biology at the University of Aveiro in Portugal.
“Everything needs to be carried to the mountains and then through all the cave “¦ [and] there are no machines, only human work,” Reboleira said in an interview with LiveScience.
“At the base camp we have no freshwater, only melted snow, and the food has to be rationed to feed almost 30 persons during 30 days. Searching for cave-dwelling animals is a task that requires several hours of active search — extremely difficult in the cold conditions of the cave, because of the risk of hypothermia,” she added, noting that temperatures in the cave average between 32.9 to 41 degrees Fahrenheit.
But the team´s grueling work has apparently paid off. The previous record for the deepest known terrestrial animal was jointly held by a scorpion and silverfish discovered in a Mexican cave about 3,020 feet below the Earth´s surface. Found at a depth of some 6,500 feet, the eyeless, wingless Plutomurus ortobalaganensis smashes the prior record.
With no eyes and extremely long antennae, the tiny little springtails are morphologically similar to many species of troglobionts — or cave-dwellers — explained Enrique Baquero, a taxonomist at Spain´s University of Navarre.
One peculiarity, however, is that P. ortobalaganensis is not albino like most creatures that have evolved in caves.
“[I]t has pigment, usually absent in animals that are strict troglobionts,” said Baquero as he described the creature´s grayish, spotted body.
Baquero believes that this evolutionary oddity can likely be attributed to a relatively recent migration into the subterranean depths. Because pigments are a known to be an evolutionary defense against the sun´s harmful UV rays, it is highly probable that P. ortobalaganensis only recently — in evolutionary terms — made the move from the surface into the cave.
Given the extremely low levels of nutrients and the complete absence of light at over 6,000 feet below the Earth´s surface, Reboleira believes that her team´s finding will force biologists to rethink existing paradigms about the possibilities for life at such extreme depths
“It [deep-cave life] seems to be richer than we thought,” she said.
A report of the researchers´ findings can be found in the February 22 issue of the journal Terrestrial Arthropod Reviews.
Image Caption: Researchers discovered four new species of springtails at different depths of the cave. Shown here, the cave at 6,500 feet (1,980 meters) where the deepest springtail, Plutomurus ortobalaganensis, was discovered. Credit: Denis Provalov
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