What is "stygofauna"

n. (context zoology English) Any fauna that live within groundwater systems, such as caves and aquifers, particularly the small, aquatic groundwater invertebrates.

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 pore 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.

1. Stygophiles inhabit both surface and subterranean aquatic environments, but are not necessarily restricted to either;
2. Stygoxenes are like stygophiles, except they are defined as accidental or occasional presence in subterranean waters. Stygophiles and stygoxenes may live for part of their lives in caves but do not complete their life cycle in them; and
3. Stygobites are obligate or strictly subterranean, aquatic animals and complete their entire life in this environment.

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.