Texella reddelli
Encyclopedia
Texella reddelli, the Bee Creek cave harvestman, is a rare species of troglobitic
harvestman that was added to the United States endangered species
list in 1988, at the same time as six other species native to the karst
ecosystem in Travis County
and Williamson County
, Texas
, USA. They inhabit areas with near 100% humidity and constant temperatures, and they prey on springtail
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
and other threats. Texella reddelli are found on both the North and South sides of the Colorado river
.
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
in Travis
and Williamson
counties in Texas.
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
." This process creates the caves that are needed to support this species. They receive their nutrients through groundwater infiltration
.
. Troglobites are thought to have evolved over the last 10,000 to 2,000,000 years, when invertebrates moved into the more stable cave environments. 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
. They require stable temperatures and often stay in remote corners or the ceiling of the cave that are the warmest.
Texella reyesi
used to be considered T. reddelli because of their similarities, but 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
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.
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
. 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.
activities that result in the alteration of natural drainage patterns can negatively effect these species. This can include altering the topography
, increasing or decreasing cover, irrigation
systems, and other activities.
Fire ants 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
.
. The troglobites require protection from contaminated ground water and other non-native predators such as fire ants.
Troglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...
harvestman that was added to the United States endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
list in 1988, at the same time as six other species native to the karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
ecosystem in Travis County
Travis County, Texas
As of 2009, the U.S. census estimates there were 1,026,158 people, 320,766 households, and 183,798 families residing in the county. The population density was 821 people per square mile . There were 335,881 housing units at an average density of 340 per square mile...
and Williamson County
Williamson County, Texas
Williamson County is a county located on both the Edwards Plateau to the west, consisting of rocky terrain and hills, and Blackland Prairies in the east consising of rich, fertile farming land, The two areas are roughly bisected by Interstate 35...
, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, USA. They inhabit areas with near 100% humidity and constant temperatures, and they prey on springtail
Springtail
Springtails form the largest of the three lineages of modern hexapods that are no longer considered insects...
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
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
and other threats. Texella reddelli are found on both the North and South sides of the Colorado river
Colorado River
The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...
.
Description
These arachnidArachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
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
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
in Travis
Travis County, Texas
As of 2009, the U.S. census estimates there were 1,026,158 people, 320,766 households, and 183,798 families residing in the county. The population density was 821 people per square mile . There were 335,881 housing units at an average density of 340 per square mile...
and Williamson
Williamson County, Texas
Williamson County is a county located on both the Edwards Plateau to the west, consisting of rocky terrain and hills, and Blackland Prairies in the east consising of rich, fertile farming land, The two areas are roughly bisected by Interstate 35...
counties in Texas.
Habitat
Bee Creek Cave Harvestman inhabit limestoneLimestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
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
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
from limestone bedrock by mildly acidic groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
." This process creates the caves that are needed to support this species. They receive their nutrients through groundwater infiltration
Infiltration (hydrology)
Infiltration is the process by which water on the ground surface enters the soil. Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour. The rate decreases as the soil becomes...
.
Troglobites
Texella reddelli is a type of troglobiteTroglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...
. Troglobites are thought to have evolved over the last 10,000 to 2,000,000 years, when invertebrates moved into the more stable cave environments. 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
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally 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 recover may have been lost before this point...
. 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. 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 to grow.Texella reyesi
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 subterranean limestone caves in Travis and Williamson Counties. It is threatened by the loss of its habitat...
used to be considered T. reddelli because of their similarities, but 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
Plateau
In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
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 karstKARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
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
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. 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. DevelopmentReal estate development
Real estate development, or Property Development, is a multifaceted business, encompassing activities that range from the renovation and re-lease of existing buildings to the purchase of raw land and the sale of improved land or parcels to others...
activities that result in the alteration of natural drainage patterns can negatively effect these species. This can include altering the topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
, increasing or decreasing cover, irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
systems, and other activities.
Fire ants 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
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
.
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 diversityGenetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
. The troglobites require protection from contaminated ground water and other non-native predators such as fire ants.
See also
- Kretschmarr Cave mold beetleKretschmarr Cave Mold BeetleThe Kretschmarr Cave mold beetle is a small mold beetle that is in the kingdom Animalia, the phylum Arthropoda, the class Insecta, the order Coleopetera , the suborder Polyphaga, the family Pselaphide ....
- Tartarocreagris texanaTartarocreagris texanaTartarocreagris texana is a species of arachnid in family Neobisiidae. It is endemic to Texas in the United States, where it is known from only two caves in Travis County. It is a federally listed endangered species of the United States....
- Tooth cave spiderTooth cave spiderThe tooth cave spider is a 1/16 inch long arachnid. It is endemic to Texas and is considered an endangered species....
- List of troglobites