Subterranean (hypogean) habitats in karst and their fauna
Finlayson, C.M., Milton, G.R., Prentice, R.C. and Davidson, N.C.
The wetland book. Volume 2
Subterranean karst systems are wetlands with a generally poor biodiversity, but species typically are ecologically specialized with a high level of endemism and heightened risk of extinction. A number of diverse habitats may develop in the three zones characterized by the extent and permanence of water within the karst voids. The subterranean environment is a relatively closed space, with restricted connections to other ecosystems, and primarily dependent upon organic material dispersed in percolating water through the fissured ceiling or carried with streams entering through sinkholes. Permanent residents of subterranean habitats (troglobionts) exhibit morphological and physiological changes that may include disappearance of skin and eye pigmentation, reduction of eyes, elongation of body appendages, and elongation of the body. Beetles and crustaceans (especially Copepoda and Amphipoda) are by far the richest groups of terrestrial and aquatic troglobionts, respectively, but diversity is still poorly described for many areas. Subterranean wetlands and their inhabitants remain poorly understood, and habitat destruction is the principal threat to hypogean fauna.