Lacy elimia
Encyclopedia
The lacy elimia also known as the lacey elimia, scientific name Elimia crenatella, 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.
is conic in shape, strongly striate, and often folded in the upper whorls
.
The shell color is dark brown to black, often purple in the aperture
, and without banding. The aperture is small and ovate. The lacy elimia is easily distinguished from other Elimia
species by a combination of characters (i.e., size, ornamentation, color).
gene, the lacy elimia was found to be very similar to the compact elimia (Elimia showalteri
). Despite their apparent close genetic relationship, the authors made no suggestion that the two species represented a single species. Upon review of Lydeard et al. (1997), Dillon suggested that additional genetic studies were needed to demonstrate the genetic uniqueness of the lacy elimia. However, the Lydeard et al. (1997) genetic study addressed only one small genetic character of the genome
(entire genetic make-up of an individual) of these species, and other characters strongly support the taxonomic status of the lacy elimia.
The two species are allopatric (do not overlap in distribution - the compact elimia occurs in the Cahaba River
, whereas the lacy elimia is found in the Coosa River
drainage), and are strikingly different in size, appearance, and behavior. The compact elimia has a large, robust, smooth shell boldly colored brown and/or green, whereas the lacy elimia has a small, delicate, darkly colored, and ornamented shell.
The lacy elimia is one of the few elimia snails in the Basin that does not exhibit clinal variation.. In addition, compact elimia are found grazing individually throughout shoal habitats, whereas the lacy elimia is usually found in tight clusters or colonies on larger rocks within a shoal. Allopatry, morphology, and behavior are strong characters supporting the species status of the lacy elimia.
The lacy elimia was historically abundant in the Coosa River
main stem from St. Clair County, Alabama
to Chilton County, Alabama
, and was also known in several Coosa River tributaries: Big Will's Creek, DeKalb County; Kelley's Creek, St. Clair County; and Choccolocco Creek and Tallaseehatchee Creek, Talladega County, Alabama.
Currently, the lacy elimia is only known to survive in three Coosa River tributaries: Cheaha Creek, Emauhee Creek, and Weewoka Creek, Talladega County, Alabama
. The species is locally abundant in the lower reaches of Cheaha Creek. This stream originates within the Talladega National Forest
; however, no specimens of the lacy elimia have been collected on United States Forest Service
lands. The species has also been found at single sites in Emauhee and Weewoka creeks, where specimens are rare, and difficult to locate.
All of these streams are variously impacted by sediments and nutrients from a variety of upstream rural, suburban, and/or urban sources. Because of their small sizes and limited flows, their water and habitat quality can be rapidly affected by local and off site pollution sources.
Basin's larger rivers (Coosa River for lacy elimia) 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.
It is associated with river or stream habitats characterized by flowing currents, and hard, clean bottoms (e.g., bedrock, boulder, gravel).
(attached algae) growing on benthic (bottom) substrates.
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 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.
Description
The lacy elimia is a small species in the family Pleuroceridae. Growing to about 1.1 centimeters (cm) (0.4 in) in length, 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...
is conic in shape, strongly striate, and often folded in the upper 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...
.
The shell color is dark brown to black, often purple in 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....
, and without banding. The aperture is small and ovate. The lacy elimia is easily distinguished from other Elimia
Elimia
Elimia is a genus of freshwater snails with an operculum, aquatic gastropod mollusks in the family Pleuroceridae. Various species are found in creeks throughout much of the eastern and central United States and the Great Lakes region of Canada...
species by a combination of characters (i.e., size, ornamentation, color).
Genetics
In a recent genetic sequence study of the 16S ribosomal RNA16S ribosomal RNA
16S ribosomal RNA is a component of the 30S subunit of prokaryotic ribosomes. It is approximately 1.5kb in length...
gene, the lacy elimia was found to be very similar to the compact elimia (Elimia showalteri
Elimia showalteri
Elimia showalteri, common name the compact elimia, is a species of freshwater snail with an operculum, an aquatic gastropod mollusk in the family Pleuroceridae.- Shell description :...
). Despite their apparent close genetic relationship, the authors made no suggestion that the two species represented a single species. Upon review of Lydeard et al. (1997), Dillon suggested that additional genetic studies were needed to demonstrate the genetic uniqueness of the lacy elimia. However, the Lydeard et al. (1997) genetic study addressed only one small genetic character of the genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
(entire genetic make-up of an individual) of these species, and other characters strongly support the taxonomic status of the lacy elimia.
The two species are allopatric (do not overlap in distribution - the compact elimia occurs 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...
, whereas the lacy elimia is found in 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...
drainage), and are strikingly different in size, appearance, and behavior. The compact elimia has a large, robust, smooth shell boldly colored brown and/or green, whereas the lacy elimia has a small, delicate, darkly colored, and ornamented shell.
The lacy elimia is one of the few elimia snails in the Basin that does not exhibit clinal variation.. In addition, compact elimia are found grazing individually throughout shoal habitats, whereas the lacy elimia is usually found in tight clusters or colonies on larger rocks within a shoal. Allopatry, morphology, and behavior are strong characters supporting the species status of the lacy elimia.
Distribution
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...
main stem from 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...
to Chilton County, 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:...
, and was also known in several Coosa River tributaries: Big Will's Creek, DeKalb County; Kelley's Creek, St. Clair County; and Choccolocco Creek and Tallaseehatchee Creek, Talladega County, Alabama.
Currently, the lacy elimia is only known to survive in three Coosa River tributaries: Cheaha Creek, Emauhee Creek, and Weewoka Creek, Talladega County, Alabama
Talladega County, Alabama
Talladega County is a county of the U.S. state of Alabama. Talladega is a Muscogee Native American word derived from TVLVTEKE, which means "border town." As of 2010, the population was 82,291...
. The species is locally abundant in the lower reaches of Cheaha Creek. This stream originates within the Talladega National Forest
Talladega National Forest
The Talladega National Forest is located in the U.S. state of Alabama and covers 392,567 acres at the southern edge of the Appalachian Mountains....
; however, no specimens of the lacy elimia have been collected on United States Forest Service
United States Forest Service
The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 155 national forests and 20 national grasslands, which encompass...
lands. The species has also been found at single sites in Emauhee and Weewoka creeks, where specimens are rare, and difficult to locate.
All of these streams are variously impacted by sediments and nutrients from a variety of upstream rural, suburban, and/or urban sources. Because of their small sizes and limited flows, their water and habitat quality can be rapidly affected by local and off site pollution sources.
Reasons for the decline
The lacy elimia 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 (Coosa River for lacy elimia) 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.
Ecology
Little is known of the ecology specific to the lacy elimia, however, common information about genus Elimia are as follows.Habitat
Elimia snails are gill-breathing snails that typically inhabit highly oxygenated waters on rock shoals and gravel bars.It is associated with river or stream habitats characterized by flowing currents, and hard, clean bottoms (e.g., bedrock, boulder, gravel).
Feeding habits
Most elimia species graze on periphytonPeriphyton
Periphyton are a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that are attached to submerged surfaces in most aquatic ecosystems. It serves as an important food source for invertebrates, tadpoles, and some fish. It can also absorb contaminants; removing them from...
(attached algae) growing on benthic (bottom) substrates.