Academic literature on the topic 'Stygobiont'

Crustaceans have successfully colonized the subterranean habitat, and many have become obligate inhabitants, occurring virtually everywhere there are interconnected voids underground. With the exception of most oniscidean isopods and a few talitrid amphipods, subterranean crustaceans inhabit water (stygobionts), where they dominate the stygofauna both in biomass and diversity of species. Four major taxonomic groups predominate: amphipods, isopods, copepods, and ostracods. Although most higher crustacean taxa have representatives in both epigean and subterranean habitats, some groups such as remipedes, thermosbaenaceans, spelaeogriphaceans, bathynellaceans, mystacocarids, and gelyelloid copepods are known only from the subterranean environment. Subterranean habitats vary physically and range from organically rich shallow habitats around seeps to cave systems more than a kilometer deep. Water quality, which can range from fresh to marine to hypersaline, static to flowing, and oxic to suboxic, impacts species distribution. Dispersal patterns in subterranean crustaceans are also diverse. Freshwater stygobiont crustaceans have narrow endemic ranges, and their dispersal is limited by saltwater. The distribution of several freshwater taxa might reflect the movement of tectonic plates. The extraordinarily diverse anchialine fauna, initially distributed along the Tethyan coast, was likely spread by vicariance due to movement of tectonic plates. Originating from epigean ancestors, many stygobionts have a marine origin. While the existence of preadaptations does not necessarily guarantee successful colonization of the subterranean habitat, a suite of characteristics is frequently observed in subterranean crustaceans, with most being weakly chitinized, lacking or with reduced eyes and pigments, and enhanced non-optic sense organs. Metabolic rates tend to be lower than in epigean crustaceans. Limited evidence indicates subterranean crustaceans are longer lived with lower reproductive potential. These adaptations make subterranean crustacean populations particularly vulnerable to anthropogenic impacts. The morphological, physiological, and life history adaptations to a subterranean existence are most likely common responses to the physical environment of each subterranean ecosystem. Extensive biodiversity and phylogeography studies are still required, and there is a pressing need to comprehend the functional role of stygofauna in subterranean waters.

Groundwater in Tafilalet supports diverse faunas (stygofauna) that include many obligate groundwater-dependent species (stygobites). Prospecting campaigns on underground fauna in Tafilalt region were collected in a database that was later used to develop distribution patterns for each species harvested. Tafilalet is characterized by low rainfall, high temperatures, and very high evaporation. Those severe climate conditions influence water availability for vegetation growth and fauna stability. The present work aims to, assess stygobiont richness in subterranean environment of Tafilalet. Species data were organized in database form and geographic information system (GIS) was used to establish geographical patterns of species and test fauna and environment parameters relationship, to identify a network of stygofauna sites priority for conservation and defined areas with high taxonomic richness and high level of endemism. Risk assessment and decision-making framework for managing groundwater-dependent ecosystems (GDEs) development are required.

A wide variety of organisms are found in subterranean habitats and they have varying degrees of dependence and permanence in these habitats. Some species, stygobionts and troglobionts, have an obligate dependence on subterranean habitats, and are found nowhere else. Other species have an obligate dependence on caves and other subterranean habitats, such as bats and aquatic insects, but only spend part of their life cycle in caves (stygoxenes and trogloxenes). Others can spend their life cycle in or out of caves (stygophiles and troglophiles). There are 21 invertebrate orders that have over 50 stygobiotic and troglobiotic species. Among vertebrates, salamanders and especially fishes are also well represented in caves and deep aquifers. Although the information obtained is very informative, very few subterranean species have been maintained successfully in the laboratory. There are a few specialized collecting techniques that are very useful, especially in non-cave subterranean habitats.

A critical factor of the subterranean fauna and one that increases the risk of extinction is geographical rarity. Some stygobionts and troglobionts are also numerically rare. Subterranean organisms are also at increased risk of extinction because of low reproductive rates, and in the case of bats, because of their propensity to cluster in large numbers in a few caves. Threats to the subterranean fauna are of four general kinds—alteration of the physical habitat, changes in water quality and quantity, direct changes to the subterranean fauna, and global warming. The selection of sites for preservation requires detailed inventory data, but available evidence suggests that a majority of species can be protected at least at one site and that a relatively small percentage of total land area is required. A variety of mechanisms are available for site protection, including listing as a Ramsar wetland and as a UNESCO world heritage site.

Globally, for troglobionts, southern Europe, especially the Dinaric karst, and the Canary Islands are regions of high richness. For stygobionts, southern Europe, especially the Dinaric karst, is a hotspot. Other sites are typically chemoautotrophic and/or phreatic. In Europe and North America, there appears to be a ridge of high troglobiotic and stygobiotic diversity in southern Europe and the southeast United States that corresponds to an area of long-term high surface productivity. In Europe, local diversity is a small component of regional stygobiotic diversity and the importance of spatial heterogeneity, historical climate stability, and productivity are both scale and spatially dependent. Habitat availability seems especially important at smaller scales. The analogy with islands in ecological time is most appropriate at scales smaller than caves, such as seeps or epikarst drips, and the analogy with caves in evolutionary time is more appropriate at larger scales, such as karst basins or contiguous karst areas.