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10 creatures that thrive in caves

By: Bryan Nelson on Jan. 10, 2011, 1:08 p.m.
Devil's hole pupfish

Photo: Stan Shebs/Wiki Commons/GNU

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Devil's hole pupfish

This fish is so rare that it is found only in a single aquifer-fed pool within a limestone cavern in Death Valley National Park. (This picture represents its entire natural range.)

Despite relying on a shallow limestone shelf of only 2 meters (6.6 feet) by 4 meters (13 feet) for spawning, it has survived as a species for at least 22,000 years.