Search Field Guide
Advanced Search
MT Gov Logo
Montana Field Guide

Montana Field Guides

Bedford Springsnail - Pyrgulopsis bedfordensis

No photos are currently available
If you have a high quality photo of this species, are confident in the identification, and would like to submit it for inclusion on the Montana Field Guide, please send it to us using our online photo submission tool.

Species of Concern
Native Species

Global Rank: G1
State Rank: S1
(see State Rank Reason below)

Agency Status

External Links

State Rank Reason (see State Rank above)
Due to this restricted distribution and only known occurrence, this species was given a conservation status rank, G1 (Globally Rare) and placed on the MT Species of Concern list as S1, critically imperiled
General Description
Tiny, operculate snails (2-5 mm in height) usually endemic to thermally-warmed springs in the western U.S. Pyrgulopsis is the largest genus of freshwater gastropods in North America.

Pygurlopsis bedfordensis: shell ovate-conic, protoconch about 1.25 whorls, empty shell clear white, periostracum brown or tan, aperture ovate to pyriform, inner lip slightly thickened, columellar lip strongly reflected, outer lip thin, umbilicus narrowly perforate and often obscured by columellar lip; operculum medium thickness, light amber with darker red hue in nuclear region, ovate; cephalic tentacles gray to black, head and foot brown to dark brown. Shell height 2.94-3.69 mm, shell width 1.99-2.30 mm, aperture (height x width) 1.31-1.59 x 1.27-1.47 mm, total shell whorls >4.0-5.0, width of body whorl 1.71-2.10 mm, shell width/shell height 0.58-0.70 (Hershler and Gustafson 2001); Shell height 2.29-3.30 mm, shell width 1.53-2.06 mm, aperture (height x width) 1.12-1.54 x 0.95-1.23 mm, total shell whorls 4.25-5.0, width of body whorl 1.29-1.81 mm, shell width/shell height 0.62-0.73 Hershler et al. 2008).

Adults presumably active throughout the year.

Diagnostic Characteristics
Small and globose with an operculum; compared to P. blainica (the only other member of the genus in Montana, and restricted to a single Madison County spring), P. bedfordensis typically smaller in all shell dimensions, teleoconch whorls less convex, aperture more angular at adapical end, columellar shelf wider, also with differences in genitalia (larger penial lobe, smaller penial filament, absence of a ventral penial gland), narrower central cusps on central radular teeth, and mtDNA sequences; shell ratios of P. bedfordensis larger than P. blainica, with shell width 58-73% of shell height (vs 51-69%) and aperture height 45-54% of shell height (vs 32-47%) (Hershler and Gustafson 2001; Hershler et al. 2008).

Species Range
Montana Range


Range Comments
Montana endemic: restricted to a single warm spring (on private property) on the west side of Canyon Ferry Reservoir, Broadwater County, at about 1190 m elevation (Hershler and Gustafson 2001; Stagliano 2016). This is the first species of the genus found on the east side of the Continental Divide.

Observations in Montana Natural Heritage Program Database
Number of Observations: 4

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)


Found on the substrate (sand, gravel and cobbles) and aquatic plants in the discharge of a single warm spring (21.0-23.6 C) on the west side of Canyon Ferry Reservoir. Very dense population sampled in 2015, average densities of the springsnail were 30,540 live individuals per meter squared (SE = ±2,625) and 17,353 dead individuals per meter squared (SE = ± 1,389). Snail shells literally carpeted the bottom substrate of the spring channel (Hershler and Gustafson 2001; Stagliano 2016).

Food Habits
Not described. Freshwater aquatic snails are mostly scrapers of algae and other photosynthetic biofilms on underwater surfaces (rocks, aquatic plants).

Reproductive Characteristics
Sexes separate, not hermaphroditic. Other than anatomy of male and female reproductive systems (Hershler and Gustafson 2001), reproductive characteristis not described.

The riparian habitat and water recharge to the spring where it is found should be protected.

Threats or Limiting Factors
Damage to the riparian habitat or any harmful discharges (chemicals, pollutants, etc.) into the water recharge area of the spring where this species is found could have detrimental effects on the one population in the state.

Login Logout
Citation for data on this website:
Bedford Springsnail — Pyrgulopsis bedfordensis.  Montana Field Guide.  .  Retrieved on , from