Leptoxis ampla
Encyclopedia
Leptoxis ampla, common name
the round rocksnail, is a species
of freshwater snail
with a gill
and an operculum
, an aquatic
gastropod mollusk in the family Pleuroceridae
.
This species is endemic to the United States
, specifically the state of Alabama
. The snail has been listed as threatened on the United States Fish and Wildlife Service list of endangered species
since October 28 1998.
Leptoxis ampla is a vulnerable species according to the IUCN Red list, but its synonym Elimia ampla is written up as being critically endangered species according to the IUCN Red list.
grows to about 20 mm (0.8 in) in length. The shell is subglobose, with an ovately rounded aperture
. The body whorl
is shouldered at the suture, and may be ornamented with folds or plicae. Color may be yellow, dark brown, or olive green, usually with four entire or broken bands.
Lydeard et al. (1997) found slight differences in DNA sequencing
between the painted rocksnail
and the round rocksnail, and considered them to be sister species. Following analysis by allozyme
electrophoresis
on these same species, Dillon speculated that the two species represented isolated population
s belonging to a single species. The two species are geographically separated, with the painted rocksnail inhabiting Coosa River
tributaries, while the round rocksnail is the only surviving rocksnail species in the Cahaba River
drainage. Both species are currently recognized by the malacological community.
and the Little Cahaba River, Bibb County, Alabama
; and the Coosa River
, Elmore County, Alabama
, and tributaries—Big Canoe
and Kelly's creeks, St. Clair County, Alabama
; Ohatchee Creek, Calhoun County, Alabama
; Yellowleaf Creek, Shelby County, Alabama
; and Waxahatchee Creek
, Shelby/Chilton counties, Alabama
.
The round rocksnail is currently known from a shoal series in the Cahaba River, Bibb and Shelby counties, Alabama, and from the lower reach of the Little Cahaba River, and the lower reaches of Shade and Six-mile creeks in Bibb County, Alabama.
Basin's larger rivers (Cahaba River, Coosa River and its triburaties for round rocksnail) is primarily due to extensive construction of dam
s, and the subsequent inundation of the snail's shoal habitats by the impounded waters. This snail has disappeared from all portions of its historic habitats that have been impounded by dams.
Dams change such areas by eliminating or reducing currents, and thus allowing sediments to accumulate on inundated channel habitats. Impounded waters also experience changes in water chemistry, which could affect survival or reproduction of riverine snails. For example, many reservoirs in the Basin currently experience eutrophic (enrichment of a water body with nutrients) conditions, and chronically low dissolved oxygen levels. Such physical and chemical changes can affect feeding, respiration, and reproduction of these riffle and shoal snail species.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
the round rocksnail, 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 freshwater snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
with a gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
and an operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
, an aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
gastropod mollusk in the family Pleuroceridae
Pleuroceridae
Pleuroceridae, common name pleurocerids, is a family of small to medium-sized freshwater snails, aquatic gilled gastropod mollusks in the superfamily Cerithioidea.These snails have an operculum and typically a robust high-spired shell....
.
This species is endemic to the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, specifically the state of Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
. The snail has been listed as threatened on the United States Fish and Wildlife Service list of endangered species
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 October 28 1998.
Leptoxis ampla is a vulnerable species according to the IUCN Red list, but its synonym Elimia ampla is written up as being critically endangered species according to the IUCN Red list.
Description
The round rocksnail is a pleurocerid snail and its 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...
grows to about 20 mm (0.8 in) in length. The shell is subglobose, with an ovately rounded 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....
. The body whorl
Body whorl
Body whorl is part of the morphology of a coiled gastropod mollusk.- In gastropods :In gastropods, the body whorl, or last whorl, is the most recently-formed and largest whorl of a spiral or helical shell, terminating in the aperture...
is shouldered at the suture, and may be ornamented with folds or plicae. Color may be yellow, dark brown, or olive green, usually with four entire or broken bands.
Lydeard et al. (1997) found slight differences in DNA sequencing
DNA sequencing
DNA sequencing includes several methods and technologies that are used for determining the order of the nucleotide bases—adenine, guanine, cytosine, and thymine—in a molecule of DNA....
between the painted rocksnail
Painted rocksnail
The painted rocksnail, scientific name Leptoxis taeniata, is a species of freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Pleuroceridae....
and the round rocksnail, and considered them to be sister species. Following analysis by allozyme
Allozyme
Variant forms of an enzyme that are coded by different alleles at the same locus are called allozymes. These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci....
electrophoresis
Electrophoresis
Electrophoresis, also called cataphoresis, is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field. This electrokinetic phenomenon was observed for the first time in 1807 by Reuss , who noticed that the application of a constant electric...
on these same species, Dillon speculated that the two species represented isolated population
Population
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...
s belonging to a single species. The two species are geographically separated, with the painted rocksnail inhabiting Coosa River
Coosa River
The Coosa River is a tributary of the Alabama River in the U.S. states of Alabama and Georgia. The river is about long altogether.The Coosa River is one of Alabama's most developed rivers...
tributaries, while the round rocksnail is the only surviving rocksnail species in the Cahaba River
Cahaba River
The Cahaba River is the longest free-flowing river in Alabama and is among the most scenic and biologically diverse rivers in the United States. The Cahaba River is a major tributary of the Alabama River and part of the larger Mobile River Basin...
drainage. Both species are currently recognized by the malacological community.
Distribution
The round rocksnail was historically found in the Cahaba RiverCahaba River
The Cahaba River is the longest free-flowing river in Alabama and is among the most scenic and biologically diverse rivers in the United States. The Cahaba River is a major tributary of the Alabama River and part of the larger Mobile River Basin...
and the Little Cahaba River, Bibb County, Alabama
Bibb County, Alabama
Bibb County is a county in the U.S. state of Alabama. Its name is in honor of William W. Bibb, the first Governor of Alabama. As of 2010 the population was 22,915. The county seat is Centreville...
; and the Coosa River
Coosa River
The Coosa River is a tributary of the Alabama River in the U.S. states of Alabama and Georgia. The river is about long altogether.The Coosa River is one of Alabama's most developed rivers...
, Elmore County, Alabama
Elmore County, Alabama
Elmore County is a county of the State of Alabama. Its name is in honor of General John A. Elmore. As of 2010 its population was 79,303. Its county seat is Wetumpka.This county is part of the Montgomery Metropolitan Statistical Area.- History :...
, and tributaries—Big Canoe
Big Canoe
Big Canoe is the 1986 solo album released by former Split Enz frontman Tim Finn. This album was the first time that Tim had worked with Split Enz co-founder Phil Judd since Judd left the band in 1978. In interviews Tim has said that the idea was that he and Phil were intending on writing again,...
and Kelly's creeks, St. Clair County, Alabama
St. Clair County, Alabama
St. Clair County is a county of the U.S. state of Alabama.It is a part of the Birmingham–Hoover–Cullman Combined Statistical Area. Its name is in honor of General Arthur St...
; Ohatchee Creek, Calhoun County, Alabama
Calhoun County, Alabama
Calhoun County is a county in the U.S. state of Alabama. Its name is in honor of John C. Calhoun, famous member of the United States Senate from South Carolina. As of 2010 the population was 118,572. It is included in the Anniston-Oxford Metropolitan Statistical Area...
; Yellowleaf Creek, Shelby County, Alabama
Shelby County, Alabama
Shelby County is a county of the U.S. state of Alabama and a part of the Birmingham–Hoover–Cullman Combined Statistical Area. It is named in honor of Isaac Shelby, Governor of Kentucky. The county seat of Shelby County is Columbiana. As of 2010 U.S. Census the population was 195,085. Shelby...
; and Waxahatchee Creek
Waxahatchee Creek
Waxahatchee Creek is a tributary of the lower Coosa River near Shelby, Alabama. The lower reaches of Waxahatchee Creek are broad and popular with water skiers and recreational boaters. Several resort camps and marinas are located on the creek, and anglers have found the submerged forests of the...
, Shelby/Chilton counties, Alabama
Chilton County, Alabama
-2010:Whereas according to the 2010 U.S. Census Bureau:*84.1% White*9.7% Black*0.4% Native American*0.3% Asian*0.0% Native Hawaiian or Pacific Islander*1.2% Two or more races*7.8% Hispanic or Latino -2000:...
.
The round rocksnail is currently known from a shoal series in the Cahaba River, Bibb and Shelby counties, Alabama, and from the lower reach of the Little Cahaba River, and the lower reaches of Shade and Six-mile creeks in Bibb County, Alabama.
Reasons for the decline
The round rocksnail has disappeared from more than 90 percent of its historic range. The curtailment of habitat and range for this (and few other snail species) species in the MobileMobile River
The Mobile River is located in southern Alabama in the United States. Formed out of the confluence of the Tombigbee and Alabama rivers, the approximately river drains an area of of Alabama, with a watershed extending into Mississippi, Georgia, and Tennessee. Its drainage basin is the...
Basin's larger rivers (Cahaba River, Coosa River and its triburaties for round rocksnail) is primarily due to extensive construction of dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
s, and the subsequent inundation of the snail's shoal habitats by the impounded waters. This snail has disappeared from all portions of its historic habitats that have been impounded by dams.
Dams change such areas by eliminating or reducing currents, and thus allowing sediments to accumulate on inundated channel habitats. Impounded waters also experience changes in water chemistry, which could affect survival or reproduction of riverine snails. For example, many reservoirs in the Basin currently experience eutrophic (enrichment of a water body with nutrients) conditions, and chronically low dissolved oxygen levels. Such physical and chemical changes can affect feeding, respiration, and reproduction of these riffle and shoal snail species.