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Texas blind salamander

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The San Marcos River rises from the San Marcos Springs , the location of the Meadows Center for Water and the Environment (formerly Aquarena Springs), in San Marcos, Texas . The springs are home to several threatened or endangered species, including the Texas blind salamander , fountain darter , and Texas wild rice . The river is a popular recreational area, and is frequented for tubing , canoeing , swimming , and fishing .

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51-598: The Texas blind salamander ( Eurycea rathbuni ) is a rare and endangered cave -dwelling troglobite amphibian native to San Marcos , Hays County, Texas , specifically the San Marcos Pool of the Edwards Aquifer . This species resembles the olm , another stygofaunal salamander from Europe. Unlike the olm, this amphibian's body is not as elongated, and also has less reduced digits on its limbs (the olm only has three digits on its front limbs, and two on

102-551: A clear, gelatinous base that is about four times longer than it is wide. The species is found to have a delayed reproductive maturity and low reproductive output, with females found to produce 5, small egg clutches on average per year. Populations of Texas blind salamander are sensitive to groundwater pollution. They are additionally vulnerable to depletion of groundwater resources, which occurs over time when withdrawals for commercial or domestic purposes exceed aquifer recharge through percolation, etc. Long-term groundwater availability

153-426: A distinctive landform known as karst , characterized by sinkholes and underground drainage. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation . These include flowstones , stalactites , stalagmites , helictites , soda straws and columns. These secondary mineral deposits in caves are called speleothems . The portions of a solutional cave that are below

204-558: A hollow tube remains. Such caves can be found in the Canary Islands , Jeju-do , the basaltic plains of Eastern Idaho , and in other places. Kazumura Cave near Hilo , Hawaii is a remarkably long and deep lava tube; it is 65.6 km long (40.8 mi). Lava caves include but are not limited to lava tubes. Other caves formed through volcanic activity include rifts, lava molds, open vertical conduits, inflationary, blisters, among others. Sea caves are found along coasts around

255-420: A modern understanding of acoustics. Archaeologists have uncovered relationships between paintings of dots and lines, in specific areas of resonance, within the caves of Spain and France, as well as instruments depicting paleolithic motifs, indicators of musical events and rituals. Clusters of paintings were often found in areas with notable acoustics, sometimes even replicating the sounds of the animals depicted on

306-510: A newly constructed well that drew water from 58 metres (190 ft) below the surface. The time of breeding is poorly documented. Dunn (1926) noted a specimen maintained in the laboratory laid a few eggs on March 15 and a specimen collected in early fall had the spermatheca packed with spermatozoa . Very small juveniles have been found throughout the year, suggesting a seasonal breeding pattern. Bechler (1988) observed one complete and two partial courtship bouts in captive specimens in which

357-508: A pale or white coloration), a loss of eyes (or at least of optical functionality), an elongation of appendages, and an enhancement of other senses (such as the ability to sense vibrations in water). Aquatic troglobites (or stygobites), such as the endangered Alabama cave shrimp , live in bodies of water found in caves and get nutrients from detritus washed into their caves and from the feces of bats and other cave inhabitants. Other aquatic troglobites include cave fish, and cave salamanders such as

408-532: A particular geographical area that contains all of the physical, chemical and biological attributes needed for the continued success of an endangered plant or animal and that may require special efforts for their management and protection. Much of the San Marcos River is protected by the Edwards Aquifer habitat conservation plan due to the wildlife that reside in or near the river. This plan

459-453: A range of early human species dating back to between three and one million years ago, including Australopithecus africanus , Australopithecus sediba and Paranthropus robustus . However, it is not generally thought that these early humans were living in the caves, but that they were brought into the caves by carnivores that had killed them. The first early hominid ever found in Africa,

510-409: A right angle to the body while the female continues rubbing the base of the tail. The male then leads the female forward, bends his body into an S-shaped pattern, and deposits a spermatophore on the substrate. He next leads the female forward with the tail extended laterally until she picks up the spermatophore cap with her cloacal lips. The spermatophore consists of a crescent-shaped white sperm cap over

561-415: A stream sinks"), outflow caves ("from which a stream emerges"), and through caves ("traversed by a stream"). Solutional caves or karst caves are the most frequently occurring caves. Such caves form in rock that is soluble; most occur in limestone , but they can also form in other rocks including chalk , dolomite , marble , salt, and gypsum . Except for salt caves , solutional caves result when rock

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612-474: Is a natural void under the Earth 's surface . Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance underground (such as rock shelters ). Caves which extend further underground than the opening is wide are called endogene caves . Speleology is the science of exploration and study of all aspects of caves and

663-662: Is being monitored using the flow of the San Marcos River as a surrogate measure. As of 2004, the population trend of the Texas blind salamander is stable, according to the IUCN. A five-year review published in 2021 identified all downlisting criteria as being "partially complete", but warned that current groundwater withdrawal limits do not take into account the likelihood of increasing frequency and intensity of droughts due to climate change . Cave A cave or cavern

714-448: Is characterized by prominent dark stripes along its body. Its population is unknown, as no samples have been collected since 1983, and is even considered to be extinct. Both fish require clear, clean, continually flowing water with a stable temperature. An endangered plant species specific to the San Marcos River is Texas wild rice . Only 230 clumps still remain on the river in two different populations, with one population being grown on

765-547: Is dependent on the topography of the landscape above it. For karst caves the maximum depth is determined on the basis of the lower limit of karst forming processes, coinciding with the base of the soluble carbonate rocks. Most caves are formed in limestone by dissolution . Caves can be classified in various other ways as well, including a contrast between active and relict: active caves have water flowing through them; relict caves do not, though water may be retained in them. Types of active caves include inflow caves ("into which

816-444: Is dissolved by natural acid in groundwater that seeps through bedding planes , faults , joints, and comparable features. Over time cracks enlarge to become caves and cave systems. The largest and most abundant solutional caves are located in limestone. Limestone dissolves under the action of rainwater and groundwater charged with H 2 CO 3 ( carbonic acid ) and naturally occurring organic acids . The dissolution process produces

867-906: Is not known if this salamander has any natural predators, however the stygobitic catfish Satan eurystomus also lives in Edwards Aquifer, so it might be a potential predator. However, due to the limited range of that fish, it might not come into contact with the amphibian. Specimens have been collected at seven localities in the Purgatory Creek system and along the San Marcos Fault near San Marcos, Texas . Adults and immature larvae are well-adapted for living in underground streams in caves, and many probably inhabit deep recesses that are not accessible to collectors. Specimens have been taken in deep pools with minimal current and nearly constant 21–22 °C (70–72 °F) temperatures. The first specimens of this species were collected in 1895 from

918-631: The Denisovans in southern Siberia. In southern Africa, early modern humans regularly used sea caves as shelter starting about 180,000 years ago when they learned to exploit the sea for the first time. The oldest known site is PP13B at Pinnacle Point . This may have allowed rapid expansion of humans out of Africa and colonization of areas of the world such as Australia by 60–50,000 years ago. Throughout southern Africa, Australia, and Europe, early modern humans used caves and rock shelters as sites for rock art, such as those at Giant's Castle . Caves such as

969-783: The Madagascar dry deciduous forests and parts of Brazil contain many documented caves. As the world's expanses of soluble bedrock are researched by cavers, the distribution of documented caves is likely to shift. For example, China, despite containing around half the world's exposed limestone—more than 1,000,000 square kilometres (390,000 sq mi)—has relatively few documented caves. Cave-inhabiting animals are often categorized as troglobites (cave-limited species), troglophiles (species that can live their entire lives in caves, but also occur in other environments), trogloxenes (species that use caves, but cannot complete their life cycle fully in caves) and accidentals (animals not in one of

1020-605: The Taung Child in 1924, was also thought for many years to come from a cave, where it had been deposited after being predated on by an eagle. However, this is now debated (Hopley et al., 2013; Am. J. Phys. Anthrop.). Caves do form in the dolomite of the Ghaap Plateau, including the Early, Middle and Later Stone Age site of Wonderwerk Cave ; however, the caves that form along the escarpment's edge, like that hypothesised for

1071-680: The Texas Water Safari . The history and naming of the river is somewhat unclear. It may have been discovered by Alonso de León 's expedition in 1689, but some scholars believe they instead had found the Colorado or Navidad Rivers . The convention came to call the first sizable river beyond the Guadalupe, but at the time, the Comal River was often called the Guadalupe, and part of the Guadalupe often called San Ybón. In 1808,

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1122-536: The olm and the Texas blind salamander . Cave insects such as Oligaphorura (formerly Archaphorura) schoetti are troglophiles, reaching 1.7 millimetres (0.067 in) in length. They have extensive distribution and have been studied fairly widely. Most specimens are female, but a male specimen was collected from St Cuthberts Swallet in 1969. Bats , such as the gray bat and Mexican free-tailed bat , are trogloxenes and are often found in caves; they forage outside of

1173-456: The very slow flow of the ice, which tends to collapse the caves again. Glacier caves are sometimes misidentified as " ice caves ", though this latter term is properly reserved for bedrock caves that contain year-round ice formations. Fracture caves are formed when layers of more soluble minerals, such as gypsum, dissolve out from between layers of less soluble rock. These rocks fracture and collapse in blocks of stone. Talus caves are formed by

1224-486: The water table or the local level of the groundwater will be flooded. Lechuguilla Cave in New Mexico and nearby Carlsbad Cavern are now believed to be examples of another type of solutional cave. They were formed by H 2 S ( hydrogen sulfide ) gas rising from below, where reservoirs of oil give off sulfurous fumes. This gas mixes with groundwater and forms H 2 SO 4 ( sulfuric acid ). The acid then dissolves

1275-518: The yaodong in China were used for shelter; other caves were used for burials (such as rock-cut tombs ), or as religious sites (such as Buddhist caves ). Among the known sacred caves are China's Cave of a Thousand Buddhas and the sacred caves of Crete . Paleolithic cave paintings have been found throughout the world dating from 64,800 years old for non-figurative art and 43,900 years old for figurative art. The importance of sound in caves predates

1326-416: The San Marcos River and the Edwards Aquifer. Other endangered species include the fountain darter and San Marcos gambusia , which reside in the San Marcos River. The fountain darter is characterized by the mottled brown body and dark markings that help it camouflage into the bottom of the San Marcos River banks. It has a growing population and flourishes in the San Marcos River. The San Marcos gambusia

1377-574: The San Marcos River and the Guadalupe River, spanning from Aquarena Springs in San Marcos to Seadrift, Texas , a total of 260 miles. This event is actually composed of many parts, including an information seminar, the safari race, a preliminary race, and another short race. Racers must take enough food and provisions to last them the distance of the race. The Texas Water Safari is billed as the "World's Toughest Boat Race" and runs annually on

1428-560: The Spanish established San Marcos de Neve, just south of present-day San Marcos. They had friendly relations with the Tonkawa Indians, but the hostile Comanche tribe forced them to leave in 1812. In 1998 and 2015, the river was affected by severe flooding. San Marcos hosts many events on the San Marcos River. The Texas Water Safari event has run every year since 1963; it uses canoes powered only by human muscle. This event uses

1479-780: The Taung Child, are formed within a secondary limestone deposit called tufa . There is numerous evidence for other early human species inhabiting caves from at least one million years ago in different parts of the world, including Homo erectus in China at Zhoukoudian , Homo rhodesiensis in South Africa at the Cave of Hearths ( Makapansgat ), Homo neanderthalensis and Homo heidelbergensis in Europe at Archaeological Site of Atapuerca , Homo floresiensis in Indonesia, and

1530-508: The Texas River Protection Association, and is usually the first Saturday of every March. San Marcos has many different wildlife species, including endangered ones, that reside in the San Marcos River. Species are listed threatened or endangered based on declining numbers or loss of habitat. The Texas blind salamander and the San Marcos salamander are endangered species that are only found in certain section of

1581-713: The Texas State University campus. The San Marcos River is considered to be one of the most biologically diverse aquatic ecosystems known in the Southwestern United States . Consequently, the United States Fish and Wildlife Service and Texas Parks and Wildlife Department have designated the San Marcos Springs and Spring Lake critical habitat, so some parts of the river are privatized. Critical habitat refers to

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1632-557: The back). The species has a broad, flat snout and head, and vestigial eyes beneath that are covered by skin. Like other neotenous salamanders , it has external gills for absorbing oxygen from the water. The salamander's mature length is around 13 cm (5 in). The forelimbs carry four digits and the hind limbs possess five digits. The species is found to be able to regenerate its tail and limbs if they are lost. Its diet varies by what flows into its cave, and includes blind shrimp ( Palaemonetes antrorum ), snails, and amphipods . It

1683-542: The cave environment. Visiting or exploring caves for recreation may be called caving , potholing , or spelunking . The formation and development of caves is known as speleogenesis ; it can occur over the course of millions of years. Caves can range widely in size, and are formed by various geological processes. These may involve a combination of chemical processes, erosion by water, tectonic forces, microorganisms, pressure, and atmospheric influences. Isotopic dating techniques can be applied to cave sediments, to determine

1734-586: The caves utilized for reverberation, but for the dampening qualities of their abnormal faces as well. The irregularities in the walls of the Cumberland Caverns diffuse sounds bouncing off the walls and give the space an almost recording studio-like quality. During the 20th century musicians began to explore the possibility of using caves as locations as clubs and concert halls, including the likes of Dinah Shore , Roy Acuff , and Benny Goodman . Unlike today, these early performances were typically held in

1785-565: The caves. Some species of cave crickets are classified as trogloxenes, because they roost in caves by day and forage above ground at night. Because of the fragility of cave ecosystems, and the fact that cave regions tend to be isolated from one another, caves harbor a number of endangered species, such as the Tooth cave spider , liphistius trapdoor spider , and the gray bat. Caves are visited by many surface-living animals, including humans. These are usually relatively short-lived incursions, due to

1836-424: The female initiated courtship and the male remained passive initially. Courtship begins when the female approaches the male and rubs her chin on his dorsum . The female may also rub her cloaca on nearby rocks while rocking to and fro. If the male does not respond, the female may nip the male along the sides or engage in kicking behavior in which gravel is scratched with the hind limbs. The female eventually straddles

1887-532: The headwaters is restricted because of the delicate ecosystem and numerous rare species. The upper river flows through San Marcos, and is a popular recreational area. It is joined by the Blanco River after four miles, and passes through Luling and Palmetto State Park . Near Gonzales , it flows into the Guadalupe River after a total of 75 miles (121 km). This course is the first section of

1938-562: The lack of light and sustenance. Cave entrances often have typical florae. For instance, in the eastern temperate United States, cave entrances are most frequently (and often densely) populated by the bulblet fern, Cystopteris bulbifera . People have made use of caves throughout history. The earliest human fossils found in caves come from a series of caves near Krugersdorp and Mokopane in South Africa. The cave sites of Sterkfontein , Swartkrans , Kromdraai B, Drimolen , Malapa , Cooper's D, Gladysvale, Gondolin and Makapansgat have yielded

1989-413: The limestone from below, rather than from above, by acidic water percolating from the surface. Caves formed at the same time as the surrounding rock are called primary caves . Lava tubes are formed through volcanic activity and are the most common primary caves. As lava flows downhill, its surface cools and solidifies. Hot liquid lava continues to flow under that crust, and if most of it flows out,

2040-464: The main focus of the restoration projects in a large effort to protect the Edward Aquifer. Non-native plants are uprooted and new plants are planted to take their spots. Also, six new access points were to be added to the river in attempts to allow people to get in and out of the water without harm to the river banks. The city was to spend close to $ 1 million in this restoration attempt, to makes

2091-412: The mouths of the caves, as the lack of technology made depths of the interior inaccessible with musical equipment. In Luray Caverns , Virginia, a functioning organ has been developed that generates sound by mallets striking stalactites, each with a different pitch. San Marcos River The river begins at San Marcos Springs, rising from the Edwards Aquifer into Spring Lake . Access to much of

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2142-465: The openings among large boulders that have fallen down into a random heap, often at the bases of cliffs. These unstable deposits are called talus or scree , and may be subject to frequent rockfalls and landslides . Anchialine caves are caves, usually coastal, containing a mixture of freshwater and saline water (usually sea water). They occur in many parts of the world, and often contain highly specialized and endemic fauna. Caves are found throughout

2193-428: The previous categories). Some authors use separate terminology for aquatic forms (for example, stygobites , stygophiles , and stygoxenes ). Of these animals, the troglobites are perhaps the most unusual organisms. Troglobitic species often show a number of characteristics, termed troglomorphic, associated with their adaptation to subterranean life. These characteristics may include a loss of pigment (often resulting in

2244-480: The second Saturday of June. Another event is the San Marcos River annual San Marcos River Clean-Up, which is an organized spring clean-up of the whole river. Volunteers can either clean debris around the river with the use of canoes, or cook food for the San Marcos River Clean-Up thank-you dinner that is provided for all volunteers. The clean-up is coordinated yearly by Tom Goynes, president of

2295-415: The tail of the male and rubs her snout above the tail base. The male responds by arching his pelvic region and fanning his tail between her legs. The female then rubs her snout more rapidly over the base of the tail. The male may lead the female forward and repeat the same cycle while slowly vibrating the anterior third of the tail. The male eventually bends the body laterally and moves the tail laterally at

2346-400: The timescale of the geological events which formed and shaped present-day caves. It is estimated that a cave cannot be more than 3,000 metres (9,800 ft) vertically beneath the surface due to the pressure of overlying rocks. This does not, however, impose a maximum depth for a cave which is measured from its highest entrance to its lowest point, as the amount of rock above the lowest point

2397-462: The walls. The human voice was also theorized to be used as an echolocation device to navigate darker areas of the caves where torches were less useful. Dots of red ochre are often found in spaces with the highest resonance, where the production of paintings was too difficult. Caves continue to provide usage for modern-day explorers of acoustics. Today Cumberland Caverns provides one of the best examples for modern musical usages of caves. Not only are

2448-417: The water, such as a fault or joint. A subtype of the erosional cave is the wind or aeolian cave, carved by wind-born sediments. Many caves formed initially by solutional processes often undergo a subsequent phase of erosional or vadose enlargement where active streams or rivers pass through them. Glacier caves are formed by melting ice and flowing water within and under glaciers. The cavities are influenced by

2499-667: The world, although the distribution of documented cave system is heavily skewed towards those countries where caving has been popular for many years (such as France, Italy, Australia, the UK, the United States, etc.). As a result, explored caves are found widely in Europe, Asia, North America and Oceania, but are sparse in South America, Africa, and Antarctica. This is a rough generalization, as large expanses of North America and Asia contain no documented caves, whereas areas such as

2550-791: The world. A special case is littoral caves, which are formed by wave action in zones of weakness in sea cliffs. Often these weaknesses are faults, but they may also be dykes or bedding-plane contacts. Some wave-cut caves are now above sea level because of later uplift. Elsewhere, in places such as Thailand 's Phang Nga Bay , solutional caves have been flooded by the sea and are now subject to littoral erosion. Sea caves are generally around 5 to 50 metres (16 to 164 ft) in length, but may exceed 300 metres (980 ft). Corrasional or erosional caves are those that form entirely by erosion by flowing streams carrying rocks and other sediments. These can form in any type of rock, including hard rocks such as granite. Generally there must be some zone of weakness to guide

2601-462: Was established in 2006 as an attempt between several Texas cities that use the many resources of the San Marcos River to manage aquatic habitats and water resources of the Comal and San Marcos springs. This plan helps manage control of non-native species, species stability, control of native species, sediment removal, reduction of contamination, and flow protection. Work on the San Marcos River banks are

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