SPECIES FACT SHEET
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 crossfertilization. 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.
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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.
Threats:
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
References:
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.
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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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