Species Common Name: High-capped lanx Species Scientific Name

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Species Common Name: High-capped lanx

Species Scientific Name: Lanx alta (Tryon 1865)

Phylum: Mollusca

Class: Gastropoda

Order: Pulmonata

Family: Lymnaeidae; Subfamily: Lancidae
OR/WA BLM and FS Region 6 Units where Suspected or Documented:

Sites documented in large tributaries to Klamath Lake and in the Klamath River on Winema NF, Klamath NF, Klamath Resource Area of the Lakeview BLM, and Redding Resource Area of Northern California BLM; and in the Rogue River on Medford BLM and Rogue-Siskiyou NF including the Rogue National Wild and Scenic River (Frest and Johannes 1991, 1995, 1996, 2000).

Technical Description:

Shell symmetrically cap-shaped (ancyliform, limpet-shaped) with concentric growth ridges; base of shell open, oval in shape, height approximately 2/3 of shell length (4.5-9 mm diameter). Shell color evenly dark red, weathering to white.

Life History:

(probably) Semelparous – lives 1-2 years, breeds and dies. Population turn over is probably greater than 90%. Animals continue to add new growth each summer, increasing diameter until death.

Freshwater pulmontates generally reproduce by copulation and cross-fertilization. Eggs are laid from spring to autumn in gelatinous capsules attached to plants, stones, or other objects. They lack a free-swimming larval stage, and hatch as young snails, anatomically complete except for the reproductive system (Hyman 1967).
Feed by scraping algae, diatoms and other perilithic organisms from rock surfaces. May occasionally feed on aquatic plant surfaces. Present all year, but not active in winter. Individuals have no lungs or gills with respiration through the mantle cavity. Have low tolerance for hypoxia and anoxia.

Range, Distribution (Current and Historic), and Abundance:

Historically distributed in drainages of the Klamath and Rogue Rivers; from Klamath County, OR, south to the Smith and Trinity Rivers in Klamath, Six Rivers and Trinity NF, in Del Norte, and Siskiyou Counties, California. Currently known only from the Klamath River and its large tributaries in OR and CA; also documented from the Rogue River in OR.

Habitat Associations:

Found in larger tributaries and rivers, on upper surfaces of boulders and bedrock outcrops in fast current. Generally not found below 3 m depth. Species requires high oxygen content, so is not found in impoundments, or where water is warm, slow, nutrient-enriched or turbid. Habitat generally limited to cold, fast-flowing, clear waters, especially in areas influenced by cold spring input.


Impoundments created by dams and other structures which create oxygen-poor conditions can create unsuitable habitat for this species. Waste-water drainage into rivers can also create nutrient-rich conditions which are unfavorable to this species. Areas with high peak flow regimes may experience scouring of bedrock and boulder habitats, removing animals from rock surfaces.

Conservation Considerations:

Maintenance of natural hydrologic conditions, by managing for historic vegetation and water-retention capacity of soils in upland areas can prevent loss of animals due to scouring during peak flow events. Limit water-treatment outflow and fertilizer runoff into rivers which may add nutrients and other pollutants to water.

Prepared by: Nancy Duncan, April 2008

Edited by: Rob Huff, January 2009

Frest, T. J., and E. J. Johannes. 1991. Present and potential candidate mollusks occurring within the range of the northern spotted owl. Deixis Consultants, Seattle, WA. 30 pp.
Frest, T. J., and E. J. Johannes. 1995. Interior Columbia Basin mollusk species of special concern. Final report: Interior Columbia Basin Ecosystem Management Project, Walla Walla, WA. Deixis Consultants, Seattle, WA. Contract #43-0E00-4-9112. 274 pp. plus appendices.
Frest, T. J., and E. J. Johannes. 1996. Freshwater Mollusks of the Upper Klamath Drainage, Orgeon. Deixis Consultants, Seattle, WA. 219 pp. plus appendices.
Frest 2000, Baseline Mollusk Survey of Southwestern Oregon, with Emphasis on the Rogue and Umpqua River Drainages, Deixis Consultants, Seattle, WA.
Tryon, G.W. 1865. Descriptions of new species of North American Lymnaeidae. American Journal of Conchology 1: 223-231.

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