Stygofauna

Last updated
Astyanax jordani, a cavefish from Mexican caves Astyanax jordani.jpg
Astyanax jordani , a cavefish from Mexican caves

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.

Contents

  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 don't complete their life cycle in them.
  3. Stygobites are obligate, or strictly subterranean, aquatic animals and complete their entire life in this environment. [1]

Extensive research of stygofauna has been undertaken in countries with ready access to caves and wells such as France, Slovenia, the US and, more recently, Australia. Many species of stygofauna, particularly obligate stygobites, are endemic to specific regions or even individual caves. This makes them an important focus for the conservation of groundwater systems.

Diet and lifecycle

The Alabama cavefish, (Speoplatyrhinus poulsoni) AlabamaCavefish.jpg
The Alabama cavefish, (Speoplatyrhinus poulsoni)

Stygofauna have adapted to the limited food supply and are extremely energy efficient. Stygofauna feed on plankton, bacteria, and plants found in streams. [2]

Orconectes australis, a cave crayfish Orconectes australis (Marshal Hedin).jpg
Orconectes australis , a cave crayfish

To survive in an environment where food is scarce and oxygen levels are low, stygofauna often have very low metabolism. As a result, stygofauna may live longer than other terrestrial species. For example, the crayfish Orconectes australis from Shelta Cave in Alabama can reproduce at 100 years and live to 175. [3]

The Tumbling Creek cavesnail (Antrobia culveri) is a typical stygobite: small, white and blind. Antrobia culveri.jpg
The Tumbling Creek cavesnail (Antrobia culveri) is a typical stygobite: small, white and blind.

Distribution and species

Stygofauna are found all over the world and include turbellarians, gastropods, isopods, amphipods, decapods, fishes, or salamanders.

Stygofaunal gastropods are found in the U.S, Europe, Japan, [4] and Australia. Stygobite turbellarians can be found in North America, Europe and Japan. [4] Stygobite isopods, amphipods and decapods are found widely around the world.

Cave salamanders are found in Europe and the U.S, but only some of these (such as the olm and Texas blind salamander) are entirely aquatic.

The approximately 170 species of stygobite fish, popularly known as cavefish, are found in all continents, except Antarctica, but with major geographical differences in the species richness. [5] [6]

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 (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. [7] 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). [7] [8] 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

Related Research Articles

Cave Natural underground space large enough for a human to enter

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 also refer to much smaller openings such as sea caves, rock shelters, and grottos, though strictly speaking a cave is exogene, meaning it is deeper than its opening is wide, and a rock shelter is endogene.

Plankton Organisms that are in the water column and are incapable of swimming against a current

Plankton are the diverse collection of organisms found in water that are unable to propel themselves against a current. The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish and whales.

Amblyopsidae

The Amblyopsidae are a fish family commonly referred to as cavefish, blindfish, or swampfish. They are small freshwater fish found in the dark environments of caves, springs and swamps in the eastern half of the United States. Like other troglobites, most amblyopsids exhibit adaptations to these dark environments, including the lack of functional eyes and the absence of pigmentation. More than 200 species of cavefishes are known, but only six of these are in the family Amblyopsidae. One of these, Forbesichthys agassizii, spends time both underground and aboveground. A seventh species in this family, Chologaster cornuta, is not a cave-dweller but lives in aboveground swamps.

Benthos

Benthos, from the Greek benthos meaning "depth of the sea", is the community of organisms that live on, in, or near the seabed, river, lake, or stream bottom, also known as the benthic zone. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.

Amphipoda Order of malacostracan crustaceans

Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from 1 to 340 millimetres and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far described. They are mostly marine animals, but are found in almost all aquatic environments. Some 1,900 species live in fresh water, and the order also includes terrestrial animals and sandhoppers such as Talitrus saltator.

Isopoda Order of arthropods

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, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax.

Edwards Aquifer

The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of the Edwards Plateau in the U.S. state of Texas, it is the source of drinking water for two million people, and is the primary water supply for agriculture and industry in the aquifer's region. In addition, the Edwards Aquifer feeds the Comal and San Marcos springs, provides springflow for recreational and downstream uses in the Nueces, San Antonio, Guadalupe, and San Marcos river basins, and is home to several unique and endangered species.

Troglofauna

Troglofauna are small cave-dwelling animals that have adapted to their dark surroundings. Troglofauna and stygofauna are the two types of subterranean fauna. Both are associated with subterranean environments – troglofauna are associated with caves and spaces above the water table and stygofauna with water. Troglofaunal species include spiders, insects, myriapods and others. Some troglofauna live permanently underground and cannot survive outside the cave environment. Troglofauna adaptations and characteristics include a heightened sense of hearing, touch and smell. Loss of under-used senses is apparent in the lack of pigmentation as well as eyesight in most troglofauna. Troglofauna insects may exhibit a lack of wings and longer appendages.

Alabama cavefish

The Alabama cavefish is a critically endangered species of amblyopsid cavefish found only in underground pools in Key Cave, located in northwestern Alabama, United States in the Key Cave National Wildlife Refuge. It was discovered underneath a colony of gray bats in 1967 by researchers Robert A. Kuehne and John E. Cooper and scientifically described in 1974.

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land, as compared with aquatic animals, which live predominantly or entirely in the water, or amphibians, which rely on a combination of aquatic and terrestrial habitats. Terrestrial invertebrates include ants, flies, crickets, grasshoppers and spiders.

Assemblages of plants and invertebrate animals of tumulus springs of the Swan Coastal Plain are ecological communities in Western Australia. They have been managed under a number of other, similar names, including Mound springs of the Swan Coastal Plain and Communities of Tumulus Springs . The tumulus mounds were common to a narrow range of groundwater discharge at the boundary of 'bassendean sand' and 'guildford clay', along the edge of the Gnangara Mound aquifer. The communities are critically endangered.

The Georgia blind salamander is a species of salamander in the family Plethodontidae. It is endemic to the south-eastern United States where its natural habitats are inland karsts, caves and subterranean habitats. It is listed as "Vulnerable" by the IUCN and is threatened by habitat loss.

Charles Chilton (zoologist)

Charles Chilton was a New Zealand zoologist, the first rector to be appointed in Australasia, and the first person to be awarded a D.Sc. degree in New Zealand.

Mesograzers are defined as small invertebrate herbivores less than 2.5 cm in length, and can include juveniles of some larger species. The feeding behaviour of these small invertebrate herbivores is what classifies them as mesograzers. They are commonly found abundantly on Microalgae, seagrass beds, giant kelp, and coral reefs globally, since these are their main food sources and habitats. Their foraging behaviour is grazing on the organism they are living on, where there are typically masses reaching tens of thousands of mesograzers per meter of habitat. They experience predation from micro-carnivorous fish that help regulate the population of kelp and other common food sources of mesograzers by controlling the population of mesograzers; consequently, grazing is an important process linking aquatic vegetation to higher trophic level. Mesograzers show important top-down effect on marine communities, depending on the diversity and presence of predators. Mesograzers are typically overlooked in scientific research however their foraging effects have been suggested to have extreme effects on the population of their common food sources. They both positively and negatively affect macroalgal performance and productivity through grazing on algal, or through removing epiphytes. Mesograzers typically exist in spaces lacking enemies by inhabiting, therefore consuming, marine vegetation which are defended against more mobile, larger consumers through chemical defenses.

Deep-sea gigantism

In zoology, deep-sea gigantism is the tendency for species of invertebrates and other deep-sea dwelling animals to be larger than their shallower-water relatives across a large taxonomic range. Proposed explanations for this type of gigantism include colder temperature, food scarcity, reduced predation pressure and increased dissolved oxygen concentrations in the deep sea. The inaccessibility of abyssal habitats has hindered the study of this topic.

Crustacean larva

Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.

Subterranean fauna

Subterranean fauna refers to animal species that are adapted to live in underground environment. Troglofauna and stygofauna are the two types of subterranean fauna. Both are associated with hypogean habitats – troglofauna is associated with terrestrial subterranean environment, and stygofauna with all kind of subterranean waters.

<i>Xibalbanus tulumensis</i>

Xibalbanus tulumensis is a venomous, hermaphroditic crustacean found in anchialine caves on the Yucatán Peninsula in the Caribbean Sea. This blind remipede liquefies the body contents of other crustaceans with a venom similar to that of rattlesnakes, and which includes digestive enzymes and a paralysing toxin.

Biospeleology

Biospeleology, also known as cave biology, is a branch of biology dedicated to the study of organisms that live in caves and are collectively referred to as troglofauna.

References

  1. Rubens M. Lopes, Janet Warner Reid, Carlos Eduardo Falavigna Da Rocha (1999). "Copepoda: developments in ecology, biology and systematics: proceedings of the Seventh international conference on Copepoda, held in Curitiba". Hydrobiologia. Springer. 453/454: 576. ISBN   9780792370482.CS1 maint: multiple names: authors list (link)
  2. Thomas C. Barr Jr. (1967). "Observations on the ecology of caves". The American Naturalist . 101 (922): 475–491. doi:10.1086/282512. JSTOR   2459274.
  3. Kevin Krajick (September 2007). "Discoveries in the dark". National Geographic .
  4. 1 2 Thomas C. Barr Jr. & John R. Holsinger (1985). "Speciation in cave faunas". Annual Review of Ecology and Systematics . 16: 313–337. doi:10.1146/annurev.es.16.110185.001525. JSTOR   2097051.
  5. Romero, A. (2001). The Biology of Hypogean Fishes. Developments in Environmental Biology of Fishes. ISBN   978-1402000768.
  6. Behrmann-Godel, J.; A.W. Nolte; J. Kreiselmaier; R. Berka; J. Freyhof (2017). "The first European cave fish". Current Biology . 27 (7): R257–R258. doi: 10.1016/j.cub.2017.02.048 . PMID   28376329.
  7. 1 2 Environmental Protection Authority of Western Australia (2007). "Sampling methods and survey considerations for subterranean fauna in Western Australia (Technical Appendix to Guidance Statement No. 54)" (PDF). p. 32.
  8. F. Malard, ed. (2002). "Sampling Manual for the Assessment of Regional Groundwater Diversity". p. 74. Archived from the original on 2007-09-13.