Most life on Earth depends on sunlight, but inside deep caves, darkness reigns. Despite being mostly cut off from the outside world, caves shelter an amazing array of organisms.
The walls of sulfur spring caves are often coated with microbes that scientists wryly call “snottites”—slimy mats of bacteria up to half an inch thick. Instead of using energy from the Sun, as green plants do, these bacteria draw energy from sulfur compounds to make their own food. Snottites can form the foundation of an unusual ecosystem in some caves, where many animals graze on the bacteria colonies as a source of food.
Meet more cave-dwellers in Life at the Limits: Stories of Amazing Species.
Image: Kenneth Ingham/NASA