![Astyanax jordani](https://upload.wikimedia.org/wikipedia/commons/a/a2/Astyanax_jordani.jpg)
Stygofauna are any
fauna
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zoo ...
that live in
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
systems or aquifers, such as
cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s, fissures and
vug
A vug, vugh, or vugg (
) is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity (folding and faulting) are partially filled by quartz, ...
s. Stygofauna and
troglofauna
Troglofauna are small cave-dwelling animals that have adapted to their dark surroundings. Troglofauna and stygofauna are the two types of subterranean fauna (based on life-history). Both are associated with subterranean environments – troglofaun ...
are the two types of
subterranean fauna The endemic of Dinaric Alps.
Subterranean fauna refers to Animal, animal species that are adaptation, adapted to live in an underground Natural environment, environment. Troglofauna and stygofauna are the two types of subterranean fauna. Both are a ...
(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
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated.
T ...
. Stygofauna can live within freshwater
aquifer
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...
s and within the
pore
Pore may refer to:
Biology Animal biology and microbiology
* Sweat pore, an anatomical structure of the skin of humans (and other mammals) used for secretion of sweat
* Hair follicle, an anatomical structure of the skin of humans (and other m ...
spaces of
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
,
calcrete
Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, ...
or
laterite
Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...
, 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.
# Stygophiles inhabit both surface and subterranean aquatic environments, but are not necessarily restricted to either.
# 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 don't complete their life cycle in them.
# Stygobites are obligate, or strictly subterranean, aquatic animals and complete their entire life in this environment.
Extensive research of stygofauna has been undertaken in countries with ready access to caves and wells such as
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
,
Slovenia
Slovenia ( ; sl, Slovenija ), officially the Republic of Slovenia (Slovene: , abbr.: ''RS''), is a country in Central Europe. It is bordered by Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the southeast, an ...
, the
US and, more recently,
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
. Many species of stygofauna, particularly obligate stygobites, are
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to specific regions or even individual caves. This makes them an important focus for the conservation of groundwater systems.
Diet and lifecycle
![AlabamaCavefish](https://upload.wikimedia.org/wikipedia/commons/9/9e/AlabamaCavefish.jpg)
Stygofauna have adapted to the limited food supply and are extremely energy efficient. Stygofauna feed on plankton, bacteria, and plants found in streams.
![Orconectes australis (Marshal Hedin)](https://upload.wikimedia.org/wikipedia/commons/c/c3/Orconectes_australis_%28Marshal_Hedin%29.jpg)
To survive in an environment where food is scarce and oxygen levels are low, stygofauna often have very low
metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
. As a result, stygofauna may live longer than other terrestrial species. For example, the
crayfish
Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
''
Orconectes australis
''Orconectes australis'' is a species of crayfish in the family Cambaridae found in Alabama and Tennessee
Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee ...
'' from
Shelta Cave
Shelta Cave is a cave and lake located in Huntsville, Madison County, Alabama, United States. It is described as one of the most bio-diverse caves within the Appalachian Mountains. The cave is currently owned and managed as a nature preserve by t ...
in Alabama can reproduce at 100 years and live to 175.
Distribution and species
Stygofauna are found all over the world and include
turbellarian
The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from to large freshwater forms more ...
s,
gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
s,
isopods
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...
,
amphipod
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...
s,
decapods
The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is estim ...
,
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
es, or
salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...
s.
Stygofaunal gastropods are found in the U.S, Europe, Japan,
and Australia. Stygobite turbellarians can be found in North America, Europe and Japan.
Stygobite isopods, amphipods and decapods are found widely around the world.
Cave salamander
A cave salamander is a type of salamander that primarily or exclusively inhabits caves, a group that includes several species. Some of these animals have developed special, even extreme, adaptations to their subterranean environments. Some speci ...
s are found in Europe and the U.S, but only some of these (such as the
olm
The olm or proteus (''Proteus anguinus'') is an aquatic salamander in the family Proteidae, the only exclusively cave-dwelling chordate species found in Europe. In contrast to most amphibians, it is entirely aquatic, eating, sleeping, and br ...
and
Texas blind salamander
The Texas blind salamander (''Eurycea rathbuni'') is a rare cave-dwelling troglobite amphibian native to San Marcos, Hays County, Texas, specifically the San Marcos Pool of the Edwards Aquifer.
Description
The species has a broad, flat, snout ...
) are entirely aquatic.
The approximately 170 species of stygobite fish, popularly known as
cavefish
Cavefish or cave fish is a generic term for fresh and brackish water fish adapted to life in caves and other underground habitats. Related terms are subterranean fish, troglomorphic fish, troglobitic fish, stygobitic fish, phreatic fish and hypog ...
, are found in all continents, except Antarctica, but with major geographical differences in the
species richness
Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative a ...
.
Collecting stygofauna
Several methods are currently used to sample stygofauna. The accepted method is to lower a haul net, which is a weighted
plankton net
A plankton net is equipment used for collecting samples of plankton in standing bodies of water. It consists of a towing line and bridles, nylon mesh net, and a cod end. Plankton nets are considered one of the oldest, simplest and least expensi ...
(with minimum 50 µm mesh size), to the bottom of the bore, well or sinkhole and jiggled to agitate sediments at the base of the bore. The net is then slowly retrieved, filtering stygofauna out of the water column on the upward haul.
A more destructive method is to pump bore water (using a Bou-Rouch pump) through a net on the surface (referred to as the Karaman-Chappuis method).
These two methods provide animals for morphological and molecular analyses. A video camera can also be used down the hole, providing information on life-history of the organisms but, given the small size of the animals no species determinations can be made.
See also
* Cave conservation Cave conservation is the protection and restoration of caves to prevent or minimise the effects of human activities.
Some caves have delicate features that can be disturbed by changes in light levels, humidity, temperature or air flow. Caves that ...
* List of troglobites
A troglobite (or, formally, troglobiont) is an animal species, or population of a species, strictly bound to underground habitats, such as caves. These are separate from species that mainly live in above-ground habitats but are also able to live u ...
* Speleology
Speleology is the scientific study of caves and other karst features, as well as their make-up, structure, physical properties, history, life forms, and the processes by which they form (speleogenesis) and change over time (speleomorphology). ...
* Subterranean fauna The endemic of Dinaric Alps.
Subterranean fauna refers to Animal, animal species that are adaptation, adapted to live in an underground Natural environment, environment. Troglofauna and stygofauna are the two types of subterranean fauna. Both are a ...
* Trogloxene Trogloxenes or subtroglophiles, also called cave guests, are animal species which periodically live in underground habitats such as caves or at the very entrance, but cannot live exclusively in such habitats."Cave Plants and Animals". 9 December Am ...
References
{{Reflist, 28em
External links
Italian groundwater Amphipods
Origin and Age of the Marine Stygofauna of Lanzarote, Canary Islands
Freshwater animals
Cave animals
Ecology
Hydrology