Physa acuta - Draparnaud, 1805
Pewter Physa
Synonym(s): Haitia acuta (Draparnaud, 1805) ;Physella acuta (Draparnaud, 1805)
Taxonomic Status: Accepted
Related ITIS Name(s): Physa heterostropha (Say, 1817) (TSN 76682) ;Physa integra (Haldeman, 1841) (TSN 76683) ;Physella acuta (Draparnaud, 1805) (TSN 76699) ;Physella cubensis (Pfeiffer, 1839) (TSN 76707) ;Physella heterostropha (Say, 1817) (TSN 76736) ;Physella integra (Haldeman, 1841) (TSN 76738) ;Physella virgata (Gould, 1855) (TSN 76731)
Unique Identifier: ELEMENT_GLOBAL.2.815001
Element Code: IMGASL9120
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Snails
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Gastropoda Basommatophora Physidae Physa
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Concept Reference
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Concept Reference: Wethington, A.R. and C. Lydeard. 2007. A molecular phylogeny of Physidae (Gastropoda: Basommatophora) based on mitochondrial DNA sequences. Journal of Molluscan Studies, 73(3): 241-257.
Concept Reference Code: A07WET01EHUS
Name Used in Concept Reference: Physa acuta
Taxonomic Comments: The entire family Physidae is in need of revision. Preliminary work suggests that type specimens do not match figures in original descriptions or subsequent guides. At the present time it is difficult to assess the taxonomic status of most of these species. Most species appear to display a wide range of variability in shell morphology (Gordon pers. comm. 1993). There is some question as to whether this species is a North American native introduced to Europe or vice versa. Dillon et al. (2002) found no evidence of reproductive isolation between Physella acuta and the American Physella heterostropha and Physa integra indicating P. acuta is native to North America and introduced elsewhere making P. heterostropha and P. integra junior synonyms. This is supported by Anderson (2003) who also synonymizes P. heterostropha with P. acuta. Taylor (2003) lists this species as Haitia integra. Taylor (2003) also describes a new species that is potentially extinct, Physella hemphilli, based upon specimens from Coeur D'Alene Lake in Idaho, but this may be a synonym or variety of Physa heterostropha which Wethington and Lydeard (2007) synonymize with Physa acuta. A study of molecular phylogeny of the family Physidae conducted by Wethington and Lydeard (2007) resulted in proposed monophyly of the family and supported six major clades, each with a corresponding difference in penial morphology; with Physa acuta falling within the type c group. Further, Wethington and Lydeard (2007) concluded that P. acuta, P. heterostropha, P. integra, P. virgata, P. cubensis and P. integra niagarensis to constitute an exclusive clade, and all are attributed to one phylogenetic species, to which the valid name P. acuta applies.
Conservation Status
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NatureServe Status

Global Status: G5Q
Global Status Last Reviewed: 09Oct2008
Global Status Last Changed: 13Sep2004
Rounded Global Status: G5 - Secure
Reasons: This species is likely a European native that has been widely introduced around the world and is both common and abundant. This species has a wide distribution, presumed large population, occurrence in a number of protected areas, tolerance of a broad range of habitats, tolerance to habitat modification, lack of substantial immediate threats, and because it is not in decline or is unlikely to be declining fast enough to qualify for listing in a more threatened category.
Nation: United States
National Status: N5 (14Sep1999)
Nation: Canada
National Status: N4N5 (10Aug2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S5), Arkansas (SNR), California (SNR), Colorado (S2), Connecticut (S5), Florida (S5), Georgia (S5), Hawaii (SNA), Idaho (SNR), Illinois (SNR), Indiana (SNR), Iowa (SNR), Kansas (SNR), Kentucky (S5), Louisiana (SNR), Maine (SNR), Maryland (SNR), Massachusetts (S4), Michigan (SNR), Minnesota (SNR), Mississippi (SNR), Missouri (SNR), Montana (SNR), Nebraska (SNR), Nevada (SNR), New Hampshire (SNR), New Jersey (SNR), New Mexico (S4), New York (SNA), North Carolina (S5), North Dakota (SNR), Ohio (S5), Oklahoma (SNR), Pennsylvania (SNR), Rhode Island (SNR), South Carolina (SNR), South Dakota (SNA), Tennessee (S5?), Texas (S5), Vermont (SNR), Virginia (S5), West Virginia (SNA), Wisconsin (SNR), Wyoming (S4)
Canada British Columbia (S1S3), Labrador (SU), Manitoba (S3S5), New Brunswick (S5), Newfoundland Island (S4), Nova Scotia (SU), Ontario (S5), Prince Edward Island (SU), Quebec (SNR)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: Burch (1989) cites Physa acuta as occurring in Europe, Mediterranean regions, and Africa; and widely introduced into Australia, Hawaii, and the continental United States. As Physa cubensis, now considered a synonym, it is widely distributed in the West Indies, Central America, and northern South America, and it occurs throughout Florida and adjacent Alabama and Georgia (Thompson, 1999). As Physa cubensis, considered a synonym, it is widely distributed in the West Indies, Central America, and northern South America, and occurs throughout Florida and adjacent Alabama and Georgia (Thompson, 1999). Burch (1989) lists several synonyms including P. heterostropha heterostropha from Nova Scotia to Ontario; New England to Ohio, Tennessee and the Virginias; and the Bahamas; P. heterostropha halei from Illinois, Missouri, Kansas, Arkansas and Texas; P. integra integra from Quebec to Manitoba, Canada, and the Great Lakes states, Iowa, South Dakota, Tennessee, Kentucky, and West Virginia; P. integra integra morph walkeri from Quebec, Ontario and the Great Lakes states; P. integra brevispira from New York, Ohio, Wisconsin and Minnesota; P. virgata virgata from Nebraska west to California, east to Texas and into Mexico; P. virgata virgata morph parva from Iowa west to California, east to Texas and north to Kansas; P. virgata anatina from Wisconsin and South Dakota southwest to Colorado and Nevada; Texas and Arkansas north to Illinois and Nebraska; P. virgata berendti from Wyoming to California, southeast to Texas and Mexico and north to Kansas; P. virgata concolor from Manitoba and Wisconsin to Idaho; P. virgata rhyssa from California, New Mexico and Texas into Mexico. It is considered globally invasive with introduced populations in Europe, Asia, Australia (Madsen and Frandsen, 1989), Africa (Appleton, 2003), and recently Lake Titicaca in Peru (Albrecht et al., 2009).

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: > 300
Number of Occurrences Comments: Burch (1989) cites P. cubensis cubensis as Bahamas, Cuba, Jamaica, Puerto Rico, the West Indies, Honduras, and Florida; with P. cubensis peninsularis in Florida. Taylor (2003) lists Haitia [= Physa] cubensis from the Bahamas; Cuba; Jamaica; Hispaniola; Puerto Rica; less abundant in Lesser Antilles as far S as Martinique; as H. integra, Great Lakes (Minnesota, Michigan) and South Dakota and North Dakota. In Indiana, Pyron et al. (2008) list it statewide. In Missouri, Wu et al. (1997) list (as P. heterostropha) across the Ozark Region and some Prairie Region near the Mississippi River (Carter, Crawford, Dent, Hickory, Howell, Knox, Laclede, Lincoln, Morgan, Newton, Oregon, Pettis, Pike, Reynolds, Ripley, St. Louis, Ste. Genevieve, Shannon, Stone, Washington, Wright Cos.); and (as P. anatina) widely (Adair, Andrew, Atchison, Audrain, Bates, Boone, Buchanan, Caldwell, Camden, Carroll, Cass, Chariton, Clay, Cooper, Crawford, Daviess, Dent, Dunklin, Franklin, Gasconade, Harrison, Holt, Howard, Howell, Iron, Jefferson, Johnson, Lincoln, Linn, Livingston, Macon, Mississippi, Montgomery, New Madrid, Nodaway, Oregon, Pemiscot, Pettis, Phelps, Pike, Platte, Polk, Pulaski, Putnam, Ralls, Ray, Reynolds, Ripley, St. Charles, St. Francois, St. Louis, Saline, Schuyler, Scott, Shannon, Stoddard, Warren, Washington, Wayne, Worth Cos.) except SW Ozarks; and P. halei statewide (Audrain, Barry, Bates, Bollinger, Boone, Butler, Callaway, Cape Girardeau, Carroll, Carter, Cass, Clay, Cole, Cooper, Crawford, Dade, Dallas, De Kalb, Dent, Dunklin, Gasconade, Greene, Henry, Hickory, Holt, Howard, Iron, Jackson, Jefferson, Knox, Laclede, Lincoln, McDonald, Macon, Madison, Miller, Mississippi, Moniteau, Montgomery, New Madrid, Nodaway, Oregon, Ozark Pemiscot, Perry, Pettis, Pike, Randolph, Ray, Reynolds, Ripley, St. Charles, St. Francois, St. Louis, Ste. Genevieve, Saline, Scott, Shannon, Stoddard, Warren, Washington, Wayne, Webster, Wright Cos.); and (as P. peninsularis) from Holt and St. Louis Cos.; nominal acuta from Butler, Carter, Grundy, Hickory, Holt, Howell, Jackson, Linn, Oregon, and St. Francois Cos. In Alabama (as P. heterostropha) it is statewide and common (Mirarchi, 2004). Blair and Sickel (1986) documented P. integra in 2 of 44 sites and P. heterostropha in 4 of 44 sites in Land Between the Lakes (between Cumberland River (Lake Berkeley) and Tennessee River (Kentucky Lake)), Tennessee. It occurs at the Savannah River Power Plant, Aiken, South Carolina (Wood, 1982). Kentucky: Kentucky, Cumberland, Licking, Green, Salt (also Rosewater, 1959), Ohio drainages (Branson and Batch, 1981; 1983; 1987). Schwartz and Meredith (1962) list P. heterostropha on the Blackwater and Laurel Fork Rivers, West Virginia. Wu and Beetle (1995) list Wyoming (as P. heterostropha) statewide: Albany, Big Horn, Campbell, Carbon, Converse, Fremont, Goshen, Johnson, Laramie, Lincoln, Sheridan, Sublette, Sweetwater, Teton, Uinta Cos. and Yellowstone National Park; as P. integra from plains Cos. Carbon, Fremont, Hot Springs, Laramie, Natrona, and Weston, and (as P. anatina) in Hot Spring Co.. Wu and Liu (2001) list it from Cloud and Nemaha Cos., N of the Kansas River and Clark and Comanche Cos. on the SW Kansas border, Kansas. Wu and Liu (2001) list Kansas records (as P. halei) from Chautauqua, Clark, Coffey, Harvey, Jefferson, adn Phillip Cos.. Branson (1966) cites Spring River drainage, Kansas and Missouri. Wu (2005) documented it in Nebraska (as P. heterostropha) in north central Cherry, Logan, and Rock Cos.; as P. halei in Custer, Dundy, and Garden Cos.; and nominally scattered near the Mississippi and large rivers in the E in Dakota, Gage, Greeley, Keith, Nemaha, Pawnee Cos. Pearce and Evans (2008) cite Plummers Island (Middle Potomac), Maryland. In Pennsylvania, it is statewide and common (Evans and Ray, 2010).

Population Size: >1,000,000 individuals

Number of Occurrences with Good Viability/Integrity: Very many (>125)

Overall Threat Impact: Low

Short-term Trend: Increase of >10%

Long-term Trend: Increase of >25%

Environmental Specificity: Broad. Generalist or community with all key requirements common.
Environmental Specificity Comments: In a study of physid distribution across habitat gradient as a response to predators, this species was found to be most successful in ponds of intermediate depth (but generally successful under all conditions) and high predator abundance (Turner and Montgomery, 2009).

Other NatureServe Conservation Status Information

Distribution
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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Burch (1989) cites Physa acuta as occurring in Europe, Mediterranean regions, and Africa; and widely introduced into Australia, Hawaii, and the continental United States. As Physa cubensis, now considered a synonym, it is widely distributed in the West Indies, Central America, and northern South America, and it occurs throughout Florida and adjacent Alabama and Georgia (Thompson, 1999). As Physa cubensis, considered a synonym, it is widely distributed in the West Indies, Central America, and northern South America, and occurs throughout Florida and adjacent Alabama and Georgia (Thompson, 1999). Burch (1989) lists several synonyms including P. heterostropha heterostropha from Nova Scotia to Ontario; New England to Ohio, Tennessee and the Virginias; and the Bahamas; P. heterostropha halei from Illinois, Missouri, Kansas, Arkansas and Texas; P. integra integra from Quebec to Manitoba, Canada, and the Great Lakes states, Iowa, South Dakota, Tennessee, Kentucky, and West Virginia; P. integra integra morph walkeri from Quebec, Ontario and the Great Lakes states; P. integra brevispira from New York, Ohio, Wisconsin and Minnesota; P. virgata virgata from Nebraska west to California, east to Texas and into Mexico; P. virgata virgata morph parva from Iowa west to California, east to Texas and north to Kansas; P. virgata anatina from Wisconsin and South Dakota southwest to Colorado and Nevada; Texas and Arkansas north to Illinois and Nebraska; P. virgata berendti from Wyoming to California, southeast to Texas and Mexico and north to Kansas; P. virgata concolor from Manitoba and Wisconsin to Idaho; P. virgata rhyssa from California, New Mexico and Texas into Mexico. It is considered globally invasive with introduced populations in Europe, Asia, Australia (Madsen and Frandsen, 1989), Africa (Appleton, 2003), and recently Lake Titicaca in Peru (Albrecht et al., 2009).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AL, AR, CA, CO, CT, FL, GA, HIexotic, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NV, NYexotic, OH, OK, PA, RI, SC, SDexotic, TN, TX, VA, VT, WI, WV, WY
Canada BC, LB, MB, NB, NF, NS, ON, PE, QC

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
CO Saguache (08109)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
13 San Luis (13010003)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation
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Group Name: Freshwater Snails

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical or current presence of single or multiple specimens, including live specimens or recently dead shells (i.e., soft tissue still attached without signs of external weathering or staining), at a given location with potentially recurring existence. Weathered shells constitute a historic occurrence. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information.
Mapping Guidance: Unlike most freshwater mussels [possibly excepting Uniomerus tetralasmus (Say, 1831) (see Isley, 1914)], some freshwater pulmonates are able to survive in intermittent streams and ponds by settling into sediment on the bottom and aestivating in otherwise dry or frozen conditions. Some species (e.g. Stagnicola spp.) may form a sheet of mucus just within the aperture called an epiphragm that effectively seals the snail from harsh external conditions (Jokinen, 1978; Brown, 1991). For ephemeral or intermittent water species, it may be particularly difficult to define the limits of an occurrence. Movement out of the water for the purposes of aestivation is on the order of cm (Jokinen, 1978), not m or km, so this behavior should not affect separation distance between occurrences. Species that may be found in intermittent waters include: Aplexa elongata, Fossaria bulimoides, F. dalli, F. modicella, F. obrussa, F. parva, Gyraulus circumstriatus, G. crista, G. parvus, Laevapex fuscus, Physa vernalis, Physella gyrina, Planorbella campestris, Planorbula armigera, Stagnicola caperata, S. elodes, S. exilis.
Separation Barriers: Separation barriers are largely based on permanent hydrological discontinuity between water bodies, with distances of 30 meters or greater between maximum high water marks constituting a separation barrier. Additional barriers are chemical and/or physical and include any connecting water body (regardless of size) with one or more of the following on a permanent basis: no dissolved calcium content, acidity greater than pH 5, lack of dissolved oxygen, extremely high salinity such as that found in saline lakes and brine waters, or temperature greater than 45

An additional physical barrier, particularly for flowing water, is presence of upland habitat between water connections. High waterfalls and anthropogenic barriers to water flow such as dams are barriers as they limit movement in an upstream direction.

Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 2 km
Alternate Separation Procedure: Freshwater cave species (mostly prosobranchs) may occur near entrances to very deep in cave systems with specimens occurring on the undersides of small stones in riffle areas (Hershler et al., 1990). For cave species, separation distance cannot often be determined accurately due to varying degrees of accessibility to occupied cave habitat. In these instances, each cave where an observation or collection was recorded (see Minimum EO Criteria, above) constitutes an element occurrence regardless of separation distance. Multiple caves within a single hydrological cave system are each considered separately. Caves with multiple entrances and passages known to be connected, but with connecting passages too small or unsafe for human entry shall be treated as a single element occurrence when the non-negotiable portion of the cave is thought to be less than approximately 300 m linear length. Species known to occur in caves include: Amnicola cora, Antrobia spp., Antrobis spp., Antroselates spp., Dasyscias spp., Fontigens aldrichi, F. antroecetes, F. bottimeri, F. morrisoni, F. nickliniana, F. orolibas, F. prosperpina, F. tartarea, F. turritella, Holsingeria spp., Phreatodrobia spp., Stygopyrgus spp.
Separation Justification: Freshwater snails have adapted to most North American habitats including permanent standing, intermittent, and flowing waters. As a whole, pulmonates (previously Subclass Pulmonata) are better dispersers than prosobranchs (previously Subclass Prosobranchia). Pulmonates adapt better to changing temperature and oxygen concentration, resist desiccation better (use pulmonary respiration, store excreted nitrogen as urea, aestivate), and have faster crawling rates (including righting response and actual movement rate) than prosobranchs (Brown et al., 1998). Some species are more tolerant to adverse habitat conditions such as high pollution levels (e.g. Physella spp.), high altitude [e.g. Acroloxus coloradensis (Henderson, 1930)], underground cave pools and springs (e.g. Fontigens spp., Phreatodrobia spp.) and hot springs (e.g. Pyrgulopsis spp.).

Precise geographic distribution of many American freshwater snails is not known but presumably reflects past geological, geographic, and climatic change (Smith, 1989). Movements between isolated or inaccessible portions of water bodies is possible but dependent on outside, passive processes (e.g. rafting, periodic flooding, transport by vertebrates, introduction by humans). Long-distance dispersal is generally not considered when assigning separation distances as otherwise impracticably large separation distances would result.

Several factors contribute to limiting freshwater snail distribution but none apply across diverse habitats or taxa. Approximately 95% of all freshwater gastropods are restricted to waters with calcium concentrations greater than 3 mg/liter (Brown, 1991; for exceptions see Jokinen, 1983). Calcium uptake for shell construction requires energy expenditure (active transport) when calcium concentration is low, but is passive at higher concentrations (Greenaway, 1971). Typically, no known biotic or abiotic factors consistently limit the abundance or distribution of freshwater gastropods among sites (DeVries et al., 2003). At specific localities, limiting factors may include hardness, acidity, dissolved oxygen, salinity, high temperature, and food availability as associated with depth (Smith, 1989). Most species and the largest populations occur in hard, alkaline waters with normal range 20-180 ppm (Shoup, 1943; Harman, 1974). Snails are uncommon in habitats with surface acidity greater than pH 5 (see also Jokinen, 1983). Dissolved oxygen limits diversity so severely polluted waters (oxygen consumed by algae blooms) are often devoid of freshwater snails excepting pollution tolerant species. Because pulmonates can utilize atmospheric oxygen, they can exist under anaerobic conditions for longer time periods (Harman and Berg, 1971; Harman, 1974; McMahon, 1983). High salinity is limiting to freshwater gastropods and inland saline lakes generally lack an associated snail fauna. Most species (excepting hot springs species) are intolerant of temperatures greater than 45șC (McDonald, 1969; van der Schalie and Berry, 1973), a condition rarely occurring naturally. Lower temperatures are less limiting as snails have been found foraging in ice-covered waters (Harman and Berg, 1971; Harman, 1974). Most species live in the shallows, (depths less than 3 m) where food abundance is greatest. As a result, drastic water fluctuations (draw-downs) may cause declines in snail populations (Hunt and Jones, 1972).

Any contiguous, occupied stretch of suitable flowing water habitat 2 km long or greater is considered an element occurrence. Two km was chosen based upon the limited active movement capabilities of most benthic invertebrates and observed home range of freshwater snails (J. Cordeiro, personal observation) as well as the relatively short life span of most species (five years for most stream species and two years for most pond species).

Date: 18Oct2004
Author: Cordeiro, J.
Notes: Prosobranchs: Neritidae: Neritina; Viviparidae: Campeloma, Cipangopaludina, Lioplax, Tulotoma, Viviparus; Ampullariidae: Marisa, Pomacea; Pleuroceridae: Elimia, Goniobasis, Gyrotoma, Io, Juga, Leptoxis, Lithasia, Pleurocera; Thiaridae: Melanoides, Tarebia; Bithyniidae: Bithynia; Hydrobiidae: Amnicola, Antrobia, Antrorbis, Antroselates, Aphaostracon, Balconorbis, Birgella, Cincinnatia, Clappia, Cochliopa, Cochliopina, Colligyrus, Dasyscias, Eremopyrgus, Floridiscrobs, Fluminicola, Fontelicella, Fontigens, Gillia, Heleobops, Holsingeria, Hoyia, Hydrobia, Lepyrium, Littoridina, Littoridinops, Lyogyrus, Notogillia, Onobops, Paludina, Phreatoceras, Phreatodrobia, Potamopyrgus, Pristinicola, Probythinella, Pyrgophorus, Pyrgulopsis, Rhapinema, Somatogyrus, Spilochlamys, Spurwinkia, Stiobia, Stygopyrgus, Taylorconcha, Texadina, Texapyrgu, Tryonia; Assimineidae: Assiminea; Pomatiopsidae: Pomatiopsis, Heterostropha; Valvatidae: Valvata
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 09Oct2008
NatureServe Conservation Status Factors Author: Cordeiro, J.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Albrecht, C., O. Kroll, E.M. Terrazas, and T. Wilke. 2009. Invasino of ancient Lake Titicaca by the globally invasive Physa acuta (Gastropoda: Pulmonata: Hygrophila). Biological Invasions 11:1821-1826.

  • Andersen, M.D. and B. Heidel. 2011. HUC-based species range maps. Prepared by Wyoming Natural Diversity Database for use in the pilot WISDOM application operational from inception to yet-to-be-determined date of update of tool.

  • Anderson, R. 2003. Physella (Costella) acuta Draparnaud in Britain and Ireland - its taxonomy, origins and relationships to other introduced Physidae. Journal of Conchology, 38(1): 7-21.

  • Appleton, C.C. 2003. Alien and invasive fresh water Gastropoda in South Africa. African Journal of Aquatic Science 28:69-81.

  • Blair, L. and J.B. Sickel. 1986. A survey of freshwater gastropods in selected habitats of Land Between the Lakes, Kentucky and Tennessee. Transactions of the Kentucky Academy of Science, 47(1/2): 6-12.

  • Branson, B.A. 1966a. A partial biological survey of the Spring River drainage in Kansas, Oklahoma and Missouri. Part I, collecting sites, basic limnological data, and mollusks. Transactions of the Kansas Academy of Science 69(3/4): 242-293.

  • Branson, B.A. and D.L. Batch. 1981. Distributional records for gastropods and sphaeriid clams of the Kentucky and Licking Rivers and Tygarts Creek drainages, Kentucky. Brimleyana, 7: 137-144.

  • Branson, B.A. and D.L. Batch. 1983. Gastropod and Sphaeriacean clam records for streams west of the Kentucky River drainage, Kentucky. Transactions of the Kentucky Academy of Science, 44(1-2): 8-12.

  • Branson, B.A., D.L. Batch, and S.M. Call. 1987. Distribution of aquatic snails (Mollusca: Gastropoda) in Kentucky with notes on fingernail clams (Mollusca: Sphaeriidae: Corbiculidae). Transactions of the Kentucky Academy of Science, 48(3-4): 62-70.

  • Britton, D.K. and R.F. McMahon. 2004. Environmentally and genetically induced shell-shape variation in the freshwater pond snail Physa (Physella) virgata (Gould, 1855). American Malacological Bulletin, 19(1/2): 93-100.

  • Burch, J.B. 1989. North American Freshwater Snails. Malacological Publications: Hamburg, Michigan. 365 pp.

  • Colorado Hot Springs - Colorado Hot Spring Trails. Online at http://www.trails.com/stateactivity.asp?area=10541(Assessed 7 February 200&)

  • Dillon, R.T., A.R. Wethington, J.M. Rhett, and T.P. Smith. 2002. Populations of the European pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra. Invertebrate Biology, 121(3): 226-234.

  • Dillon, R.T., Jr., C.E. Earnhardt, and T.P. Smith. 2004. Reproductive isolation between Physa acuta and Physa gyrina in joint culture. American Malacological Bulletin, 19(1/2): 63-68.

  • Dillon, R.T., Jr., J.D. Robinson, T.P. Smith, and A.R. Wethington. 2005. No reproductive isolation between freshwater pulmonate snails Physa virgata and P. acuta. The Southwestern Naturalist, 50(4): 415-422.

  • Evans, R.R. and S.J. Ray. 2010. Distribution and environmental influences on freshwater gastropods from lotic systems and springs in Pennsylvania, USA, with conservation recommendations. American Malacological Bulletin 28:135-150.

  • General Status, Environment Canada. 2015. Manitoba Mollusk species list and subnational ranks proposed by an expert.

  • Johnson, P.D., A.E.Bogan, K.M. Brown, N.M. Burkhead, J.R. Cordeiro, J.T. Garner, P.D. Hartfield, D.W.Q. Lepitzki, G.L. Mackie, E. Pip, T.A. Tarpley, J.S. Tiemann, N.V. Whelan, and E.E. Strong. 2013. Conservation Status of Freshwater Gastropods of Canada and the United States.  Fisheries 38(6):247-266.

  • Liu, Hsiu-Ping. 1993. Diagnostic Genetic Loci for Species in the Genus PHYSELLA. Malacological Review, 26:1-8.

  • Madsen, H., and F. Frandsen. 1989. Teh spread of fresh water snails including those of medical and veterinary importance. Acta Tropica 46:139-149.

  • Mirarchi, R.E., et al. 2004a. Alabama Wildlife. Volume One: A Checklist of Vertebrates and Selected Invertebrates: Aquatic Mollusks, Fishes, Amphibians, Reptiles, Birds, and Mammals. University of Alabama Press: Tuscaloosa, Alabama. 209 pp.

  • Nelson Harrold, M. N., and R. P. Guralnick. 2007. A field guide to the freshwater mollusks of Colorado. Colorado Division of Wildlife, Denver, Colorado. 126 pp.

  • Paraense, W.L. and J.-P. Pointier. 2003. Physa acuta Draparnaud, 1805 (Gastropoda: Physidae): a study of topotypic specimens. Memorias do Instituto Oswaldo Cruz, 98: 513-517.

  • Pearce, T.A. and R. Evans. 2008. Freshwater Mollusca of Plummers Island, Maryland. Bulletin of the Biological Society of Washington, 15: 20-30.

  • Pyron, M., J. Beaugly, E. Martin, and M. Spielman. 2008. Conservation of the freshwater gastropods of Indiana: Historic and current distributions. American Malacological Bulletin, 26: 137-151.

  • Rosewater, J. 1959. Mollusks of the Salt River, Kentucky. The Nautilus, 73: 57-63.

  • Schwartz, F.J. and W.G. Meredith. 1962. Mollusks of the Cheat River watershed of West Virginia and Pennsylvania, with comments on present distributions. The Ohio Journal of Science, 62(4): 203-207.

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