Pyrgulopsis imperialis G1 Kings River Pyrg Critically Imperiled Distribution (Where available) 343 mi² / 888 km² Hexagon Data Not Available State/Provincial Conservation Status Presumed Extirpated (SX) Possibly Extirpated (SH) Critically Imperiled (S1) Imperiled (S2) Vulnerable (S3) Apparently Secure (S4) 200 km 100 mi Secure (S5) Esri, HERE, NPS | Powered by Esri Classification Scientific Name: Pyrgulopsis imperialis Hershler, 1998 Kingdom: Animalia Phylum: Mollusca Class: Gastropoda Order: Neotaenioglossa Family: Hydrobiidae Genus: Pyrgulopsis Concept Reference: Hershler, R. 1998. A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, western United States. Part I. Genus Pyrgulopsis. The Veliger, 41(1): 1-132. Name Used in Concept Reference: Pyrgulopsis imperialis NatureServe Unique Identifier: ELEMENT_GLOBAL.2.117353 NatureServe Element Code: IMGASJ0E10 Conservation Status NatureServe Status Global Status: G1 Global Status Last Reviewed: 9/14/1999 Global status needs review. National & State/Provincial Statuses United States: N1 S1: Nevada Other Statuses U.S. Endangered Species Act: None Committee on the Status of Endangered Wildlife in Canada (COSEWIC): None Distribution National and State/Provincial Distribution: United States : NV Endemism: endemic to a single state or province Ecology and Life History Mobility and Migration Colonial Breeder: No Non-Migrant: No Locally Migrant: No Long Distance Migrant: No Habitat Habitat Type: Freshwater Phenology Food Population / Occurrence Delineation Group Name: Freshwater Snails 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 Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.)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 kilometers Separation Distance for Suitable Habitat: 2 kilometers 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 45ºC (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: 2004-10-18 Author: Cordeiro, J. Population / Occurrence Viability See the Generic Guidelines for the Application of Occurrence Ranks (2008). References 1. Hershler, R. 1998. A systematic review of the hydrobiid snails (Gastropoda: Rissooidea) of the Great Basin, western United States. Part I. Genus Pyrgulopsis. The Veliger, 41(1): 1-132. Page Last Published: 12/4/2020.