''Texella reddelli'', the Bee Creek cave harvestman, is a rare species of

troglobitic 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 ...

harvestman The Opiliones (formerly Phalangida) are an order of arachnids colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs. , over 6,650 species of harvestmen have been discovered worldwide, although the total number of ext ...

that was added to the United States

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

list in 1988, at the same time as six other species native to the

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

ecosystem in

Travis County Travis County is located in south central Texas. As of the 2020 census, the population was 1,290,188. It is the fifth-most populous county in Texas. Its county seat is Austin, the capital of Texas. The county was established in 1840 and is na ...

and Williamson County,

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

, USA. They inhabit areas with near 100% humidity and constant temperatures, and they prey on

springtail Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ento ...

s. Since they can only be found underground, research on these creatures has been difficult. Their distribution is limited and unknown reproductive rates mean that it is possible they are especially susceptible to

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and other threats. ''Texella reddelli'' are found on both the North and South sides of the

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...

Description

These

arachnid Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroon ...

s are about 1/8 of an inch (3.175 mm) long with a yellow-brown color and long legs. Juveniles have a yellowish-white body. They live underground, have small eyes, and elongated appendages. All seven species live in the Karst

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

in Travis and Williamson counties in Texas.

Habitat

Bee Creek cave harvestman inhabit

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 ...

caves. They are only able to survive in caves that maintain stable temperatures and humidity (close to 100%). They have been found in caves both on the north and south side of the Colorado river. They live in 'karst' type of terrain in Travis County, which is formed by "dissolution of calcium carbonate from limestone bedrock by mildly acidic

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 ...

." This process creates the caves that are needed to support this species. They receive their nutrients through groundwater

infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...

Troglobites

''Texella reddelli'' is a type of

troglobite 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 ...

. These species survived in the cave environment and adapted to it. The Karst terrain created caves that were not always connected with each other. This brought about "islands" of individual populations that were disconnected for long periods of time. Over time the separate groups became different species because of the isolation. The rate at which each population speciated was different. The species that are more mobile have larger ranges and are less isolated. Since they are all still relatively close together, disturbances can make them highly susceptible to

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

. They require stable temperatures and often stay in remote corners or the ceiling of the cave that are the warmest.

Location

Since 1988 when these species were first listed as endangered, other caves containing these species have been discovered, along with new

endemic species 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 ...

. Due to the intensive requirements to find caves, much of the karst area has not been searched. To date, over 700 karst features have been located in two counties in Texas, while only 100 of these are believed to contain endangered species. While the number of locations in which these endangered species are found may increase, the total range of each species is not expected to grow. ''

Texella reyesi ''Texella reyesi'' is a rare species of arachnid known by the common name Bone Cave harvestman. It is endemic to Texas in the United States, where it lives in limestone caves in Travis and Williamson Counties. It is threatened by the loss of it ...

'' was considered ''T. reddelli'' because of their similarities, but it has since been identified as different and now is also on the endangered species list. ''Texella reddelli'' is known from only three caves in the Jollyville

plateau In geology and physical geography, a plateau (; ; ), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Often one or more sides ha ...

and four caves in the Rollingwood region. Those that were originally thought to be ''T. reddelli'', but now are renamed ''Texella reyesi'' occur in Tooth, McDonald, Weldon, and Root caves, also in Texas.

Karst

The

ecosystem in Texas is provided water by surface drainage and groundwater. The water travels rapidly through cave openings and fractures. This provides very little or no purification, which can leave the cave susceptible to pollution from contaminated water. This is a problem in certain areas where runoff can be a problem or in agricultural areas where herbicides and pesticides are used. Contaminants are one of the main threats to these species, along with urban development. In a karst ecosystem the surface communities are very important for

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

. These plant and animal communities are essential for nutrients and energy. Nutrients travel from the surface in the form of organic debris. The surface plant communities around this ecosystem can range from pasture land to woodlands. Exotic plants and animals are detrimental to native species because they compete for food and decrease overall species diversity. The surface community also serves as a buffer against temperature and moisture change and can filter out some pollutants.

Threats

The area in which the species occur is going through urban expansion at a rapid rate. Very few of the caves are capable of handling a change and many of the caves already occur close to developed areas, such as roads, schools, houses, golf courses, and commercial centers. Changes in drainage patterns along with increases in pollution could cause a collapse of caves. Although some caves have already been filled or collapsed, it is hard to estimate how many have already been lost. Elliott and Reddell (1989) estimate that 10% of caves in Travis County are destroyed every 10 years.

Development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped *Photographi ...

activities that result in the alteration of natural drainage patterns can negatively affect these species. This can include altering the

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

, increasing or decreasing cover,

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

systems, and other activities. Fire

ants Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22,00 ...

are especially detrimental to the Karst ecosystem, although the main threat to the species is loss of habitat to urban development. The fire ant is an aggressive predator and it has devastating and long lasting impacts on native ant and arthropod communities. The shallow caves makes ''Texella reddelli'' vulnerable to invasion by fire ants and other exotic species. Fire ants have been found in over 50% of the caves that are known to contain endangered species in this ecosystem. Even if the fire ants do not always directly prey upon the ''Texella reddelli'', their presence can have a negative effect on the ecosystem and species that are critical in the

food chain A food chain is a linear network of links in a food web starting from producer organisms (such as grass or algae which produce their own food via photosynthesis) and ending at an apex predator species (like grizzly bears or killer whales), det ...

Recovery

The future of these several species depends on the protection of key areas of the Karst ecosystem. Areas that are chosen should not be close together in case of a disaster and in order to protect the maximum

genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is dis ...

. The troglobites require protection from contaminated ground water and other non-native predators such as fire ants.

References

{{Taxonbar, from=Q2555267 Harvestmen Cave arachnids Animals described in 1967 Arthropods of the United States