Pyrgulopsis gibba

Surprise Valley Pyrg

Family: Hydrobiidae · Class: Gastropoda · Order: Littorinimorpha

Conservation status: G3 S1S2

The Surprise Valley pyrg is a small freshwater gastropod mollusk in the family Hydrobiidae. This aquatic snail is characterized by its small, conical shell that typically measures less than 5 millimeters in height. The shell displays a characteristic spiral structure with several whorls, and the species name 'gibba' refers to its somewhat swollen or gibbous shell shape. The Surprise Valley pyrg has an extremely restricted geographic distribution, endemic to thermal spring systems in the Great Basin region. Based on available records, this species appears to be confined to specific spring complexes in the border region of California and Nevada, with its range likely centered in or near Surprise Valley in northeastern California. The species' distribution is characteristic of many Great Basin springsnails, which evolved in isolated spring systems following the recession of ancient lakes. This pyrg inhabits thermal spring environments, occupying shallow, flowing water over gravel substrates. Like related species in the region, Surprise Valley pyrg likely requires specific water temperature ranges and flow conditions typical of geothermal springs. These habitats are characterized by consistent water temperatures, stable flows, and unique water chemistry that supports endemic fauna. The species probably occurs in areas where spring water emerges and flows over rocky or gravelly bottoms, avoiding deeper pools or areas with high sediment accumulation. As with other members of the genus Pyrgulopsis, the Surprise Valley pyrg is likely a grazer, feeding on algae, diatoms, and organic detritus coating rocks and sediments in its spring habitat. These snails typically reproduce through internal fertilization, with females depositing small numbers of eggs in the spring environment. The species probably exhibits direct development, with young snails hatching as miniature versions of adults rather than passing through a free-swimming larval stage. Seasonal activity patterns and specific reproductive timing have not been documented for this species. The conservation status of the Surprise Valley pyrg reflects the precarious situation of many Great Basin endemic springsnails. With a Global/State rank of G3 S1S2, the species is considered vulnerable globally and critically imperiled to imperiled within California. This ranking indicates that the species faces a moderate risk of extinction globally, but is at very high to high risk within the state. The primary threats to Surprise Valley pyrg likely include groundwater pumping that could affect spring flows, recreational activities around spring sites, livestock impacts, and climate change effects on spring hydrology. The species' dependence on specific thermal spring conditions makes it particularly vulnerable to habitat alterations. Water diversions, geothermal energy development, or changes in groundwater levels could significantly impact the limited habitat occupied by this endemic snail. Given the restricted range and specific habitat requirements typical of Great Basin springsnails, conservation of Surprise Valley pyrg requires protection of its spring habitat and maintenance of natural hydrological processes that sustain these unique aquatic environments.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.