Flat-spired three-toothed snail
Encyclopedia
The flat-spired three-toothed snail (Triodopsis platysayoides) — also known as the Cheat three-toothed snail after the Cheat River
in West Virginia
— is a species
of air-breathing land snail
, a terrestrial
pulmonate gastropod mollusk in the family Polygyridae
.
s of adult snails are 18–22 mm in width and 8 mm in height.
The shell of Triodopsis platysayoides is thin, is right coiled (or dextral), and translucent, with 5 whorls
. It is extremely flattened in shape. The umbilicus is open and wide.
The shell is pale brown (light horn) in color; the exterior surface of the peristome
is yellowish and punctate.
The aperture
of the shell is oblong-lunate. The lip is thickened and white. There is a thick tongue-shaped tooth in the parietal wall of the aperture.
. The type specimen is stored in the collection of the Carnegie Museum of Natural History
under number 62.23750.
The taxonomic status of T. platysayoides was subsequently questioned. In 1940 the american biologist
Henry Augustus Pilsbry
considered it to be a distinct species, and he also transferred it to the genus Triodopsis
. However, based on rather limited information, Vagvolgyi classified Triodopsis platysayoides as merely a subspecies of Triodopsis complanata in 1968. This reclassification was not widely accepted however, and in 1974 Solem concluded that the available evidence did support full species status for this snail.
Triodopsis platysayoides was confirmed as a valid species with a unique penial morphology in 1988. Species status was also confirmed in 1988 by starch-gel electrophoresis
of foot tissue, while examining evolutionary relationships among 40 species of tridopsine snails in eastern North America. Populations were divided into family trees showing the phylogenetic relationships among 18 groups of species. Nine of these groups consisted of a single species, of which Triodopsis platysayoides was one group.
.
The flat-spired three-toothed snail is found only in West Virginia, among Upper Connoquenessing sandstone
outcroppings and boulders, in a restricted area along the rim of the Cheat River gorge
. The U.S. Fish and Wildlife Service considers this snail as threatened
since 1978.
This snail is primarily active at night (nocturnal). Optimum snail activity occur during spring and early summer, especially during cool, moist weather conditions when air temperatures are between 60 and 65 degrees Fahrenheit with relative humidity greater than 85 percent.
During the daytime, the species has primarily been found on the ceiling, wall, or floor of rock structures. During the night, the snails have been found equally on both rock surfaces, and on the leaf litter near rock features. The species has been observed foraging and resting under wet leaves (next to rock structure), and moving across the leaf litter to a rock feature.
There are no known diseases of Triodopsis platysayoides.
In dry seasons the snails retreat in among the huge, scattered and split boulders just below the summit. Triodopsis platysayoides specimens are typically observed within 1 meter of a rock feature. They can be found in cool, moist, deep fissures in shale
, sandstone
and limestone
outcrops, and in talus
. The snail occurs in various outcrops of rock from the bottom of the gorge to the ridgetops.
Rock outcrops that are one meter or more in height appear to be potential habitat, as long as there are cracks and crevices that are at least one meter deep. The snail appears to prefer rock talus, but is also found in cliffline areas that contain deep, dark crevices. When the two habitats coincide (rock talus and cliffline), then Triodopsis platysayoides is more often found in the talus.
While plant associations and the ages of tree occurring at known Triodopsis platysayoides sites vary greatly, several plant species are commonly found at these sites: sweet birch
, rhododendron
, and red maple
.Some sites are covered in old growth trees, while others are occupied by saplings. In some cases, open grape arbors grow over the talus. The rock structure itself appears to be more important to the snail than the age of trees or the composition of the vegetation growing on or over the rocks.
The slope
aspect is also a factor. North and northeast slopes in the Cheat gorge provide naturally cooler and moister habitats than south and southwest facing slopes. Thus, heavy canopy
cover may be more important on south and southwest facing slopes, in order to provide shade and humidity.
s, fresh and aged pack rat
feces, lichens, mushroom
s and crickets
.
Calcium
may be a limiting factor
for this snail, especially for those snails living among sandstone habitats which are predominantly acidic. Triodopsis platysayoides has been observed feeding on aged beech leaves and catkins, which are good sources of calcium, as well on the shells of Triodopsis denotata, Mesomphix cupreus, and its own kind.
Once hatched, young snails grow rapidly, and can reach maturity within their first summer.
Triodopsis platysayoides is thought to be a relatively long-lived land snail. Based upon shell growth rings,
these snails reach maturity at 3 years in the wild, or at 2 years in captivity.
Approximately 33 to 67 % of the individuals located in the field were adults.
of Triodopsis platysayoides was known. On one occasion, 50 individuals were observed and a population of "several hundred" was estimated (in 1972). A later estimation in 1974 was that the population represented about 300 to 500 living individuals. Field surveys at this same location located only 35 individuals however.
In 1984, 12 Triodopsis platysayoides were marked and released, but no recaptures
were obtained.
Increasing numbers of the snail were noticed at Coopers Rock State Forest
after the site was fenced to control human access
. However such observation of snail numbers cannot be used to deduce trends
, as other snails show short-term fluctuations of 10 to 15 times when there is such a low population total.
Triodopsis platysayoides appears to be a relatively common snail species where it is found. Although many other species of snails have been documented coexisting with Triodopsis platysayoides, they generally do not exceed Triodopsis platysayoides numbers. In many cases, Triodopsis platysayoides was the most common snail, sometimes exceeding all other snail species combined.
Genetic samples to detect differences in populations
were taken on both sides of the gorge. The analysis had not been finished in 2007 and at that point it was not known whether populations are isolated or connected genetically.
Hikers inadvertently disrupt the leaf litter cover, and crush snails. Rock climbers, too, have killed snails and destroyed their habitat
unknowingly.
Human activities such as logging
, housing developments, and forest fires can all alter the environmental conditions that the flat-spired three-toothed snail needs to survive.
the occupied habitat, and land acquisition of approximately 1,100 acres (4,45 km²) of snail habitat. (The fence is not to keep snails inside the area, but to keep people out of the habitat of the snails.)
Currently the West Virginia Division of Natural Resources
is working with the U.S. Fish and Wildlife Service to develop a "Safe Harbor Agreement" for the snail on their properties. Additionally, they are working with private landowners to encourage protection of the snail by designing special timber management guidelines.
The state of West Virginia, the Nature Conservancy
, private landowners, and the U.S. Fish and Wildlife Service, are all sharing the effort to prevent the flat-spired three-toothed snail from sliding into extinction.
Cheat River
The Cheat River is a tributary of the Monongahela River in eastern West Virginia and southwestern Pennsylvania in the United States. Via the Monongahela and Ohio rivers, it is part of the Mississippi River watershed, ultimately draining into the Gulf of Mexico.-Geography:The Cheat is formed at...
in West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...
— is a species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a terrestrial
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...
pulmonate gastropod mollusk in the family Polygyridae
Polygyridae
Polygyridae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea.The Polygyridae make up a significant proportion of the land snail fauna of eastern North America, and are also found in western North America, northern Central America, and...
.
Description
The color of the body of the animal in this species is pale gray. The shellGastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
s of adult snails are 18–22 mm in width and 8 mm in height.
The shell of Triodopsis platysayoides is thin, is right coiled (or dextral), and translucent, with 5 whorls
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
. It is extremely flattened in shape. The umbilicus is open and wide.
The shell is pale brown (light horn) in color; the exterior surface of the peristome
Peristome
The word peristome is derived from the Greek peri, meaning 'around' or 'about', and stoma, 'mouth'. It is a term used to describe various anatomical features that surround an opening to an organ or structure. The term is used in plants and invertebrate animals, such as in describing the shells of...
is yellowish and punctate.
The aperture
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
of the shell is oblong-lunate. The lip is thickened and white. There is a thick tongue-shaped tooth in the parietal wall of the aperture.
Taxonomy
Triodopsis platysayoides is now a formally-recognized species. It was first collected by Graham Netting at Coopers Rock, and later described by Stanley Brooks as Polygyra platysayoides from the area of Coopers Rock State ForestCoopers Rock State Forest
Coopers Rock State Forest is a state forest in Monongalia and Preston counties in the U.S. state of West Virginia. Its southern edge abuts Cheat Lake and the canyon section of Cheat River, a popular whitewater rafting river in the eastern US.-History:...
. The type specimen is stored in the collection of the Carnegie Museum of Natural History
Carnegie Museum of Natural History
Carnegie Museum of Natural History, located at 4400 Forbes Avenue in the Oakland neighborhood of Pittsburgh, Pennsylvania, USA, was founded by the Pittsburgh-based industrialist Andrew Carnegie in 1896...
under number 62.23750.
The taxonomic status of T. platysayoides was subsequently questioned. In 1940 the american biologist
Biologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...
Henry Augustus Pilsbry
Henry Augustus Pilsbry
Henry Augustus Pilsbry was an American biologist, malacologist and carcinologist, among other areas of study. He was a dominant presence in many fields of invertebrate taxonomy for the better part of a century...
considered it to be a distinct species, and he also transferred it to the genus Triodopsis
Triodopsis
Triodopsis is a genus of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Polygyridae.-Species:* Triodopsis hopetonensis - magnolia three-tooth, magnolia threetooth...
. However, based on rather limited information, Vagvolgyi classified Triodopsis platysayoides as merely a subspecies of Triodopsis complanata in 1968. This reclassification was not widely accepted however, and in 1974 Solem concluded that the available evidence did support full species status for this snail.
Triodopsis platysayoides was confirmed as a valid species with a unique penial morphology in 1988. Species status was also confirmed in 1988 by starch-gel electrophoresis
Gel electrophoresis
Gel electrophoresis is a method used in clinical chemistry to separate proteins by charge and or size and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge...
of foot tissue, while examining evolutionary relationships among 40 species of tridopsine snails in eastern North America. Populations were divided into family trees showing the phylogenetic relationships among 18 groups of species. Nine of these groups consisted of a single species, of which Triodopsis platysayoides was one group.
Distribution
This species of snail is endemic to the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
The flat-spired three-toothed snail is found only in West Virginia, among Upper Connoquenessing sandstone
Pottsville Formation
The Pennsylvanian Pottsville Formation is a mapped bedrock unit in Pennsylvania, western Maryland, West Virginia, and Ohio. The formation is also recognized in Alabama. It is a major ridge-former In the Ridge-and-Valley Appalachians of the eastern United States...
outcroppings and boulders, in a restricted area along the rim of the Cheat River gorge
Cheat Canyon
Cheat Canyon — also called Cheat River Canyon or Cheat River Gorge — is a 10-mile long, forested canyon of the Cheat River at the western edge of the Allegheny Mountains in northeastern West Virginia, USA...
. The U.S. Fish and Wildlife Service considers this snail as threatened
United States Fish and Wildlife Service list of endangered species
This list contains only the bird and mammal species described as endangered by the United States Fish and Wildlife Service. It contains species not only in the U.S. and its territories, but also species only found abroad. It does not contain fish, amphibians, reptiles, plants, or invertebrates,...
since 1978.
Ecology
Little is known about the life of this animal, but the West Virginia captive breeding program and past survey efforts have provided some information.This snail is primarily active at night (nocturnal). Optimum snail activity occur during spring and early summer, especially during cool, moist weather conditions when air temperatures are between 60 and 65 degrees Fahrenheit with relative humidity greater than 85 percent.
During the daytime, the species has primarily been found on the ceiling, wall, or floor of rock structures. During the night, the snails have been found equally on both rock surfaces, and on the leaf litter near rock features. The species has been observed foraging and resting under wet leaves (next to rock structure), and moving across the leaf litter to a rock feature.
There are no known diseases of Triodopsis platysayoides.
Habitat
The snail lives in cracks and crevices in rocks, and in the surrounding leaf litter.In dry seasons the snails retreat in among the huge, scattered and split boulders just below the summit. Triodopsis platysayoides specimens are typically observed within 1 meter of a rock feature. They can be found in cool, moist, deep fissures in shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
and limestone
Limestone
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....
outcrops, and in talus
Scree
Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...
. The snail occurs in various outcrops of rock from the bottom of the gorge to the ridgetops.
Rock outcrops that are one meter or more in height appear to be potential habitat, as long as there are cracks and crevices that are at least one meter deep. The snail appears to prefer rock talus, but is also found in cliffline areas that contain deep, dark crevices. When the two habitats coincide (rock talus and cliffline), then Triodopsis platysayoides is more often found in the talus.
While plant associations and the ages of tree occurring at known Triodopsis platysayoides sites vary greatly, several plant species are commonly found at these sites: sweet birch
Sweet Birch
Betula lenta is a species of birch native to eastern North America, from southern Maine west to southernmost Ontario, and south in the Appalachian Mountains to northern Georgia.-Characteristics and habitat:It is a medium-sized deciduous tree reaching 20 m tall with...
, rhododendron
Rhododendron
Rhododendron is a genus of over 1 000 species of woody plants in the heath family, most with showy flowers...
, and red maple
Red Maple
Acer rubrum , is one of the most common and widespread deciduous trees of eastern North America. It ranges from the Lake of the Woods on the border between Ontario and Minnesota, east to Newfoundland, south to near Miami, Florida, and southwest to east Texas...
.Some sites are covered in old growth trees, while others are occupied by saplings. In some cases, open grape arbors grow over the talus. The rock structure itself appears to be more important to the snail than the age of trees or the composition of the vegetation growing on or over the rocks.
The slope
Slope
In mathematics, the slope or gradient of a line describes its steepness, incline, or grade. A higher slope value indicates a steeper incline....
aspect is also a factor. North and northeast slopes in the Cheat gorge provide naturally cooler and moister habitats than south and southwest facing slopes. Thus, heavy canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
cover may be more important on south and southwest facing slopes, in order to provide shade and humidity.
Feeding habits
Triodopsis platysayoides feeds on a varied diet of over 20 or so documented foods, including several aged leaves and flower blossoms, fresh catkinCatkin
A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated but sometimes insect pollinated . They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping...
s, fresh and aged pack rat
Pack rat
A packrat, also called a woodrat, can be any of the species in the rodent genus Neotoma. Packrats have a rat-like appearance, with long tails, large ears and large black eyes. Compared to deer mice, harvest mice and grasshopper mice, packrats are noticeably larger and are usually somewhat larger...
feces, lichens, mushroom
Mushroom
A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...
s and crickets
Cricket (insect)
Crickets, family Gryllidae , are insects somewhat related to grasshoppers, and more closely related to katydids or bush crickets . They have somewhat flattened bodies and long antennae. There are about 900 species of crickets...
.
Calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
may be a limiting factor
Limiting factor
A limiting factor or limiting resource is a factor that controls a process, such as organism growth or species population, size, or distribution. The availability of food, predation pressure, or availability of shelter are examples of factors that could be limiting for an organism...
for this snail, especially for those snails living among sandstone habitats which are predominantly acidic. Triodopsis platysayoides has been observed feeding on aged beech leaves and catkins, which are good sources of calcium, as well on the shells of Triodopsis denotata, Mesomphix cupreus, and its own kind.
Life habits
Mature snails are hermaphroditic. A mating pair will cross-fertilize, and each individual may lay eggs. They bury the eggs in soil or leaf litter. A captive colony of Triodopsis platysayoides laid small cluster of 3 to 5 eggs in the soil under the leaf litter in the spring and summer.Once hatched, young snails grow rapidly, and can reach maturity within their first summer.
Triodopsis platysayoides is thought to be a relatively long-lived land snail. Based upon shell growth rings,
these snails reach maturity at 3 years in the wild, or at 2 years in captivity.
Approximately 33 to 67 % of the individuals located in the field were adults.
Populations trends
Before 1981, only one very restricted populationPopulation
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
of Triodopsis platysayoides was known. On one occasion, 50 individuals were observed and a population of "several hundred" was estimated (in 1972). A later estimation in 1974 was that the population represented about 300 to 500 living individuals. Field surveys at this same location located only 35 individuals however.
In 1984, 12 Triodopsis platysayoides were marked and released, but no recaptures
Mark and recapture
Mark and recapture is a method commonly used in ecology to estimate population size. This method is most valuable when a researcher fails to detect all individuals present within a population of interest every time that researcher visits the study area...
were obtained.
Increasing numbers of the snail were noticed at Coopers Rock State Forest
Coopers Rock State Forest
Coopers Rock State Forest is a state forest in Monongalia and Preston counties in the U.S. state of West Virginia. Its southern edge abuts Cheat Lake and the canyon section of Cheat River, a popular whitewater rafting river in the eastern US.-History:...
after the site was fenced to control human access
Access control
Access control refers to exerting control over who can interact with a resource. Often but not always, this involves an authority, who does the controlling. The resource can be a given building, group of buildings, or computer-based information system...
. However such observation of snail numbers cannot be used to deduce trends
Population dynamics
Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes...
, as other snails show short-term fluctuations of 10 to 15 times when there is such a low population total.
Triodopsis platysayoides appears to be a relatively common snail species where it is found. Although many other species of snails have been documented coexisting with Triodopsis platysayoides, they generally do not exceed Triodopsis platysayoides numbers. In many cases, Triodopsis platysayoides was the most common snail, sometimes exceeding all other snail species combined.
Genetic samples to detect differences in populations
Population genetics
Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
were taken on both sides of the gorge. The analysis had not been finished in 2007 and at that point it was not known whether populations are isolated or connected genetically.
Vulnerability
Because of its limited range, this snail is especially vulnerable to natural or human-caused incidents that could destroy most, or even all, of its populations.Hikers inadvertently disrupt the leaf litter cover, and crush snails. Rock climbers, too, have killed snails and destroyed their habitat
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...
unknowingly.
Human activities such as logging
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...
, housing developments, and forest fires can all alter the environmental conditions that the flat-spired three-toothed snail needs to survive.
Conservation
Recovery efforts for this animal have included fencingFence
A fence is a freestanding structure designed to restrict or prevent movement across a boundary. It is generally distinguished from a wall by the lightness of its construction: a wall is usually restricted to such barriers made from solid brick or concrete, blocking vision as well as passage .Fences...
the occupied habitat, and land acquisition of approximately 1,100 acres (4,45 km²) of snail habitat. (The fence is not to keep snails inside the area, but to keep people out of the habitat of the snails.)
Currently the West Virginia Division of Natural Resources
West Virginia Division of Natural Resources
The West Virginia Division of Natural Resources is an agency of the government of the U.S. state of West Virginia. While formerly known as the cabinet-level Department of Natural Resources, it is now part of the West Virginia Department of Commerce...
is working with the U.S. Fish and Wildlife Service to develop a "Safe Harbor Agreement" for the snail on their properties. Additionally, they are working with private landowners to encourage protection of the snail by designing special timber management guidelines.
The state of West Virginia, the Nature Conservancy
The Nature Conservancy
The Nature Conservancy is a US charitable environmental organization that works to preserve the plants, animals, and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive....
, private landowners, and the U.S. Fish and Wildlife Service, are all sharing the effort to prevent the flat-spired three-toothed snail from sliding into extinction.
External links
- Triodopsis platysayoides species profile from the U.S. Fish and Wildlife Service
- Triodopsis platysayoides information from The Official World Wildlife Fund Guide to Endangered Species