SPECIES FACT SHEET
Common Name: Crooked Creek springsnail
Scientific Name: Pyrgulopsis intermedia (Tryon, 1865)
Phylum: Mollusca
Class: Gastropoda
Order: Neotaenioglossa
Family: Hydrobiidae
Technical Description:
The shell of Pyrgulopsis intermedia is ovate-conic, approximately 4.0-5.5 mm high with
4.5-5.0 whorls and is narrowly umbilicate (Hershler 1994). Overall shell is nearly
smooth except for a few spiral lines. The operculum is ovate and amber with a dark
nuclear region, and the opercular lobe is dark along sides and anterior edge. Snout and
foot are moderately gray, with darkening along the anterior and posterior edges of the
foot. Tentacles are pale with a small black internal pigment patch distal to the eyespots.
The neck is paler than the foot and snout. Penis is medium sized, with medium length
filament and lobe (Hershler 1998). For additional morphological details see Hershler
(1994, 1998).
Life History:
Specific information on the life history of this species is not available, but in general
Pyrgulopsis snails are short lived, surviving only one year, and are semelparous,
reproducing only once before death (Frest and Johannes 1995). Most coldwater snails lay
eggs that are covered with a tough membrane or capsule and are attached to stones.
Although many freshwater snails are hermaphroditic, most Hydrobiidae snails are
dioecius and have separate male and female individuals. February to May appears to be
the breeding season for many coldwater species of snails in the Pacific Coast region, and
egg laying and hatching occurs between March and July. Often eggs are laid one month
following copulation, and then eggs hatch one month later. In general these snails are
essentially sessile and do not venture far from their place of birth.
Range, Distribution, and Abundance:
Although the orginal range of this snail was thought to once be much larger, it is now
believed to be restricted to the Owyhee River basin and the Barren Valley, as well as a
couple of new sites including the Crooked Creek headspring and along the lower Owyhee
River in southeastern OR (Frest and Johannes 1995; Hershler and Liu 2009).
Habitat Associations:
This species of snail generally occurs in clear cold springs and spring-influenced creeks
with moderately swift water that have gravel-boulder substrates with Rorippa present
(Frest and Johannes 1995). P. intermedia is a perilithon feeder (feeds on algal and
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microbial films on rocks surfaces) and is a lithophile, often being found on hard rocky
surfaces.
Threats:
Because this species of snail prefers pristine springs and creeks, any activity that disrupts
such habitats where this snail is known to occur will likely negatively impact P.
intermedia. Sites where these snails are known to occur have been most heavily
damaged or even destroyed by livestock grazing (Frest and Johannes 1995). In addition,
activities that lower the water table and dry habitat, such as water diversion for domestic,
industrial or stock use, also adversely affect this snail. Groundwater mining has been
known to cause a problem as well. These snails are also sensitive to pollution, siltation,
and hypoxia. An exotic species of gastropod, the New Zealand mudsnail (Potamopyrgus
antipodarum), has been documented in Crooked Creek, Malheur County, and is abundant
in the Snake River Basin (Frest and Johannes 2003; Lysne et al. 2007).
Conservation Considerations:
Managing areas where this snail lives by restricting or prohibiting activities such as those
mentioned above will help protect this snail’s habitat. Since P. antipodarum occurs in
Crooked Creek, which is the type locality for P. intermedia, intervention to extirpate P.
antipodarum from this site is not recommended (Frest and Johannes 2003), presumably
due to potential harm that could occur to P. intermedia.
Conservation Status:
This species of snail is currently ranked G1G2, critically imperiled or imperiled due to
extreme rarity or vulnerability to extinction or extirpation at the global level and S1S1 in
Oregon (Oregon Biodiversity Information Center 2010).
Prepared by: Heather Andrews
Date: April 10, 2011
Final Edits: Rob Huff
FS/BLM Conservation Planning Coordinator
Date: May 17, 2011
ATTACHMENTS:
(1)
(2)
Map of Range and Distribution
Information Sources
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ATTACHMENT 1: Map of Range and Distribution
Map showing distributions of Pyrgulopsis species in southeastern Oregon. From Hershler and Liu
(2009).
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ATTACHMENT 2: Information Sources:
Frest, T.J. and E.J. Johannes. 1995. Interior Columbia Basin mollusk species of special
concern. Final report: Interior Columbia Basin Ecosystem Management Project.
Contrac #43-OEOO-4-9112, Walla Walla, WA.
Frest, T.J. and E.J. Johannes. 2003. Progress Report, Owyhee Mollusk Inventorty.
Vale District BLM, Vale, OR.
Hershler, R. 1994. A review of the North American freshwater snail genus Pyrgulopsis
(Hydrobiidae). Smithsonian Contributions to Zoology 554: 1-115.
Hershler, R. 1998. A systematic review of the hydrobiid snails (Gastropoda :
Rissooidea) of the Great Basin, western United States. Part I. Genus Pyrgulopsis.
Veliger 41: 1-132.
Hershler, R and H.P. Liu. 2009. New species and records of Pyrgulopsis (Gastropoda:
Hydrobiidae) from the Snake River basin, southeastern Oregon: further
delineation of a highly imperiled fauna. Zootaxa: 1-22.
Lysne, S.J., L.A. Riley, W.H. Clark and O.J. Smith. 2007. The life history, ecology,
and distribution of the Jackson Lake springsnail (Pyrgulopsis robusta Walker
1908). Journal of Freshwater Ecology 22: 647-653.
Oregon Biodiversity Information Center. 2010. Rare, Threatened and Endangered
Species of Oregon. http://orbic.pdx.edu/documents/2010-rte-book.pdf
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