Stygobite

Stygofauna are any fauna that live in groundwater systems or aquifers, such as caves, fissures and vugs. Stygofauna and troglofauna are the two types of subterranean fauna (based on life-history). Both are associated with subterranean environments – stygofauna are associated with water and troglofauna with caves and spaces above the water table. Stygofauna can live within freshwater aquifers and within the spaces of limestone, calcrete or laterite, whilst larger animals can be found in cave waters and wells. Stygofaunal animals, like troglofauna, are divided into three groups based on their life history - stygophiles, stygoxenes and stygobites.

Extensive research has been done into the stygofauna of numerous other European countries (namely France and Slovenia), the USA and more recently in Australia, due to easy accessibility of caves and wells in these regions, as well as the high diversity and numbers of animals present here. Many species of stygofauna, especially the obligate stygobites, are endemic to particular regions or even particular caves. This makes them focal points for conservation of groundwater systems.

Stygofauna have adapted to the limited food supply and are extremely energy efficient. Stygofauna feed on plankton, bacteria and plants found in streams.

To survive in an environment where food is scarce and oxygen levels are low, stygofauna often have very low metabolism. As a result, stygofauna may live longer than other terrestrial species. For example, the crayfish Orconectes australis of Shelta Cave in Alabama can reproduce at 100 years and live to 175.

Stygofauna are found all over the world, and include turbellarians, gastropods, isopods, amphipods, decapods, fishes and salamanders.

...
Wikipedia