(speleofauna), animals that inhabit caves, rock fissures, and various underground regions. The science concerned with cave fauna is biospeleology, which is closely related to or includes the science of life in underground waters, or phreatobiology.
Typical cave animals include many groups of invertebrates, as well as a few amphibians (for example, the family Proteidae) and fishes. The animals are ordinarily divided into three ecological groups: troglobionts, troglophiles, and trogloxenes. Troglobionts are permanent cave inhabitants. Troglophiles undergo a complete life cycle in caves but are also able to live outside caves under similar conditions. Trogloxenes spend only part of their life cycle in caves. Troglobionts are generally unpigmented and blind. Compared to other animals living in large underground regions, they have elongated appendages and, sometimes, enlarged bodies (cave gigantism). The metabolism of troglobionts is retarded, and their life cycle is usually extended.
Because caves ordinarily have high air humidity, the differences between conditions in the water and on land are slight. Therefore, aquatic cave animals can live for long periods out of water, and terrestrial cave animals can endure periodic flooding and, sometimes, can obtain food from the water. The temperature in caves is constant.
Because there are no green plants, life is supported by the introduction of organic remains from outside (bat guano, plant remains carried in by water) and by the activity of autotrophic chemosynthetic bacteria (for example, Perabacterium spelei in the caves of France).
Many troglobionts are relicts of more or less ancient faunas. The terrestrial cave fauna developed from animals that inhabit the forest floor, soil, and underground dens; the aquatic fauna is largely of marine origin.
S. I. LEVUSHKIN