Scientific Name: Lanx subrotunda (Tryon 1865)
Common Name: rotund lanx
Phylum: Mollusca
Class: Gastropoda
Order: Basommatophora
Family: Lymnaeidae
Taxonomic Note:
Turgeon et al.
(1998) identify this species as Lanx subrotunda , but several museum holdings and authors (e.g. Naturalis Biodiversity Center, Frest and
Johannes 2000) use the synonym Lanx subrotundata .
Conservation Status:
Global Status: G2 (June 2000)
National Status: United States (N2) (June 2000)
State Statuses: Oregon (S2)
(NatureServe 2015)
IUCN Red List: NE – Not evaluated
Technical Description:
The rotund lanx was previously described as Ancylus subrotundatus and
Ancylus subrotundus (family Ancylidae) due to its limpet-like shell (ancylid species have shells that resemble low flat cones); however, subsequent authors have placed it in the family Lymnaeidae and genus Lanx (Baker 1925; Pilsbry
1925; Turgeon et al.
1998). It is a large (length 8-12 mm), flat aquatic pulmonate snail in the family Lymnaeidae. It has a complete circumferential muscle scar, easily distinguishing species in this family from other freshwater limpets (Henderson 1936; Burch 1989; Frest and Johannes 2000). Conflicting descriptions variously place the shell’s midline apex “distinctly posteriorly”
(Frest and Johannes 2000), subposteriorly (Hannibal 1912), nearly central
(Henderson 1936; Dillon 2006), and anteriorly (Pilsbry 1925). Dillon (2006) differentiates Lanx species based on shell elevation and robustness.
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The rotund lanx’s patelliform shell has a height about half that of the shell width, lower than the similar Lanx alta . Shell height is also two-thirds of shell length. The shell is pigmented reddish-brown or cinnamon in color, rarely with white streaks. Older specimens may have a yellowish color at the periphery
(Frest and Johannes 2000). Tryon (1865) described the shell as oval, nearly round and fragile.
Life History:
The rotund lanx is a freshwater snail lacking gills, ctenidia, and lung-like structures, breathing instead through a vascularized mantle (Pilsbry 1925;
Frest and Johannes 2005). Although the specific mode of breeding and reproduction is unstudied in this species, basommatophoran snails generally reproduce sexually, and lymnaeids in particular are hermaphroditic. They generally lay long, sausage-shaped egg masses, likely in the spring. Eggs are attached to plants and rocks (Brown 2001; Smith 2001). The life span of this species is unknown; however, a typical life span of snails in the lymnaeid family is between 9 and 15 months, though some lymnaeids may live as long as
2 to 4 years (Smith 2001). Frest and Johannes (2005) report that lancids, unlike other lymnaeids, reproduce just once during a one-year life cycle. They also report small egg capsules containing fewer than 12 eggs.
Lymnaeids are considered “microherbivores,” whose diet consists of algae and diatoms scraped from rocks and macrophytes (Brown 2001). Many aspects of this species’ life history are not well understood.
Range, Distribution, and Abundance:
Range : The five members of this genus, the rotund lanx ( Lanx subrotunda Tryon
1865); highcap lanx ( Lanx alta Tryon 1865); scale lanx ( Lanx klamathensis
Hannibal 1912); kneecap lanx ( Lanx patelloides Lea 1856); and Banbury
Springs limpet ( Lanx sp. 1), are restricted to western states (NatureServe 2015).
This species has been identified within the Umpqua River and Rogue River drainages of southwestern Oregon, which originate in the Cascade mountain range and cross through the Coast range to the Pacific Ocean. It has been reported in multiple reaches, including those of the North Umpqua, South
Umpqua, and mainstem Umpqua rivers, several small creeks, and the Rogue
River at Grants Pass and Gold Hill.
Although Frest and Johannes (2000) do not report this species as inhabiting the Rogue basin, records of this species exist from the Rogue basin (Henderson
1936; MCZ:Mala:114581; ORNHIC 2015). In their 2005 report, Frest and
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Johannes note the need for more critical examination of Rogue populations to determine whether Lanx species in this basin correspond to alta or subrotunda .
One record in the NRIS database from 2010 also places this species in the
Williamson River in the Klamath Basin, although this is outside of the range reported by NatureServe (2015) and Frest and Johannes (2000), and more than
60 miles from the next closest documented population. However, several museum records also place this species in the Klamath Basin, California (Haas
1953; RMNH.MOL.237455; RMNH.MOL.237456; FMNH:88734 ).
Distribution : This species has been reported in Douglas County, Josephine
County, and Jackson County. Records include sites in the North Umpqua
(Duncan 2006), near Winchester (Henderson 1936; Frest and Johannes 2000),
Winston, and near Steamboat and Swamp creeks on the Umpqua National
Forest (Frest and Johannes 2000). One record in the South Umpqua is located near the town of Myrtle Creek (Frest and Johannes 2000), although a 2006 mollusk survey in portions of the South Umpqua did not report this species
(Duncan 2006). Sites in the mainstem Umpqua include near Elkton
(Henderson 1936; Frest and Johannes 2000), Scottsburg (CAS:IZ:79014), at the mouth of Calapooya Creek (Frest and Johannes 2000) and other locations near the town of Umpqua (Duncan). Three records are reported by Frest and
Johannes (2000) and Duncan (OR/WA BLM 2015) at Cow Creek, near Beatty
Creek RNA.
This species has been reported in Josephine County, in the Rogue River (but see discussion above) at Grants Pass (Henderson 1936; MCZ:Mala:60502), and in Jackson County at Gold Hill (MCZ:Mala:114581). It has also been reported near the Oregon Caves National Monument in Cave Creek, a tributary to the
Illinois River, which is itself a tributary to the Rogue River (ORNHIC 2015).
This species has also been reported in Klamath County, in the Williamson
River (see discussion above).
The current species distribution appears to be scattered and local (Duncan, personal communication; Frest and Johannes 2000, NatureServe 2015).
BLM/Forest Service Land: This species is documented on the Roseburg District
BLM, in the South River Resource Area and the Swiftwater Resource Area. It is also suspected on the Coos Bay District BLM, as it is known to occur in the
Umpqua River downslope from BLM lands in the Umpqua Resource Area. This species is suspected on the Medford District BLM based on a vague locality in the Rogue River near Gold Hill, where the Ashland Resource Area and Butte
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Falls Resource Area meet, and a vague locality in the Rogue River near Grants
Pass, in the Grants Pass Resource Area.
This species is suspected on the Rogue-Siskiyou National Forest; the only known location on the Forest was recently ceded to the National Park Service in the expansion of the Oregon Caves National Monument to include the Oregon
Caves National Preserve (Burns, pers. comm.) The species is documented on the Umpqua National Forest, in the North Umpqua Wild and Scenic River, and elsewhere. This species is also documented on the Fremont-Winema National
Forest in the Williamson River. This species may occur on the Siuslaw National
Forest based on a vague locality near Scottsburg.
Abundance: Among their observations, Frest and Johannes (2000) report populations of this species from rare to common/abundant. One site included only dead specimens. Recent (2007/2008) surveys by Duncan et al.
report populations of 20,000 to 50,000 individuals in the North Umpqua River and
4,000 individuals in Cow Creek; in the Umpqua River, Duncan et al.
observed a density of 50 per square meter (OR/WA BLM 2015). Haas (1953) reported the species as “very plentiful” in the Rogue River at Grants Pass in Josephine
County.
Habitat Associations:
The rotund lanx is found in unpolluted rivers and large streams at low to moderate elevations (280 to 1140 meters; ~900 to 3700 feet), in highly oxygenated, swift-flowing, cold water on stable cobble, boulder or bedrock substrates and in deeper channels, and macrophytes and epiphytic algae are generally rare to absent at sites for this species (Frest and Johannes 2000). It is not found in pools or slow water locations with sediment or silt deposition, or in sites that are exposed during low water conditions (Frest and Johannes
2000; Duncan 2006). This species was recommended by Frest and Johannes
(1993) for federal listing as “endangered.”
Threats:
Many sites have been affected by logging, siltation, impoundment, and water withdrawals, potentially impacting water quality at known sites (Frest and
Johannes 2000). Urbanization is another threat to the species (NatureServe
2015). Nonindigenous species are also linked to gastropod imperilment
(Johnson et al.
2013), and multiple nonindigenous mollusks are present in the
Umpqua and Rogue basins (USGS 2015). Suction dredge mining may also affect this species through a number of different mechanisms, including
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habitat alteration, sediment transport and deposition, and associated human impacts (Harvey and Lisle 1998).
Conservation Considerations:
Research: In their 2005 report, Frest and Johannes note the need for more critical examination of Rogue populations to determine whether Lanx species in this basin correspond to alta or subrotunda . The most recent occurrence documented in the Rogue Basin dates to 1997, and this species’ presence in the Rogue basin should be considered more fully. A recent record also places this species in the Klamath Basin. Detailed specimen observations or collection for genetic analysis should be prioritized, particularly for specimens outside the
Umpqua Basin.
Inventory: Many records of this species date from the 1990s or earlier. Updated surveys at known sites will provide valuable information about the current status, range, and population characteristics of this species. Comparing records of nonindigenous aquatic species to known L. subrotunda sites will also provide valuable information for conservation and management.
Management: In areas managed for multiple purposes, avoid or minimize conversion of habitat, whether directly or indirectly through impacts to water quality (temperature, dissolved oxygen) or water quantity. Activities that result in siltation, sedimentation, or reduced flow may also impact this species’ habitat, and populations may be especially affected by activities that disturb the stream banks and bed. As this species is distributed in patchy populations, these activities may inordinately affect species’ occurrence and distribution.
Nonpoint source pollution, including urban or agricultural runoff and pesticides, may also reduce water quality. Limit these impacts where possible and monitor their effects. If insecticide or herbicide use is planned for areas where this species occurs, assess alternatives to their use. Management actions taken on lands upslope from rivers and creeks where this species is documented or suspected may affect populations through impacts to aquatic habitat.
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Version 2:
Prepared by: Emilie Blevins
Xerces Society for Invertebrate Conservation
Date: March 2015
Edited by: Sarina Jepsen
Xerces Society for Invertebrate Conservation
Date: March 2015
Final edits: Rob Huff
Interagency Sensitive and Special Status Species Program
Date: June 2015
Version 1:
Prepared by: Theresa Stone
Umpqua National Forest
December 2009
Edited by: Rob Huff
FS/BLM Conservation Planning Coordinator
May 2010
ATTACHMENT 1: References
ATTACHMENT 2: List of pertinent or knowledgeable contacts
ATTACHMENT 3: Map of species’ occurrence
ATTACHMENT 4: Photographs of this species
ATTACHMENT 5: Aquatic Gastropod Survey Protocol, including specifics for this species
ATTACHMENT 1: References
Baker, H. B. 1925. Anatomy of Lanx, a limpet-like Lymnaeid mollusk.
Proceedings of the California Academy of Sciences , 4 th Series 14(8): 143-169.
Brown, K. M. 2001. Mollusca: Gastropoda, in Thorp, J.H., and Covich, A.P., eds., Ecology and classification of North American freshwater invertebrates , 2 nd edition: San Diego, Academic Press, p. 297-329.
Burch, J. B. 1989. North American Freshwater Snails. Malacological
Publications , Hamburg, MI. 365 pp.
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Burns, S.L.. Personal communication with Rob Huff, June 5, 2015. Steve
Burns is a fishery biologist on the Wild Rivers Ranger District, Rogue River-
Siskiyou National Forest.
Dillon, R. T. 2006. The Xerces Society Pacific Northwest Taxonomic Workshop.
Missoula, Montana May 11-12, 2006 - Gastropoda.
Duncan, N. personal communication with Theresa Stone. 2005 and 2006 mussel inventory.
Duncan, N. 2006. Mussel survey techniques and results of 2006 surveys in the
Umpqua Basin, Douglas County, OR. Unpublished report. USDI Bureau of
Land Management, Roseburg, OR. 8 pp.
Frest, T. J. and E. J. Johannes. 1993. Mollusk Species of Special Concern
Within the Range of the Northern Spotted Owl. Final Report to Forest
Ecosystem Management Working Group, USDA Forest Service. Deixis
Consultants, Seattle, Washington. 98 pp.
Frest, T.J. and E. J. Johannes. 2000. A Baseline Mollusk Survey of
Southwestern Oregon, with Emphasis on the Rogue and Umpqua River
Drainages. Deixis Consultants, Seattle, Washington. Oregon Natural Heritage
Program, Portland, Oregon.
Frest, T.J. and E. J. Johannes. 2005. Grazing effects on springsnails, Cascade-
Siskiyou National Monument, Oregon, 2004 Report. Deixis Consultants,
Seattle, Washington. 188 pp.
Haas, F. Non-marine mollusks from the Pacific slope of North America.
1953/1954 The Nautilus 67(3): 95-96.
Hannibal, H. 1912. A synopsis of the recent and Tertiary fresh-water Mollusca of the Californian Province, based upon an ontogenetic classification.
Proceedings of the Malacological Society of London 10: 112-211.
Harvey, B. C. and T. E. Lisle. 1998. Effects of Suction Dredging on Streams: a
Review and an Evaluation Strategy. Fisheries 23(8): 8-17.
Henderson, J. 1936. The Non-marine Mollusca of Oregon and Washington. The
University of Colorado Studies 17(2): 47-190.
Johnson, P. D., A. E. Bogan, K. M. Brown, N. M. Burkhead, J. R. Cordeiro, J.
T. Garner, P. D. Hartfield, D. A. W. Lepitzki, G. L. Mackie, E. Pip, T. A. Tarpley,
J. S. Tiemann, N. V. Whelan and E. E. Strong. 2013. Conservation Status of
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Freshwater Gastropods of Canada and the United States. Fisheries 38: 247-
282.
National Resource Information System (NRIS), Natural Resource Manager,
USFS. [February 2015]. FishWildlife_Observation.
NatureServe. 2015. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, VA. U.S.A. Available http://explorer.natureserve.org. (Accessed: February 2015).
Oregon Natural Heritage Information Center. [February 2015]. Biotics, Element
Occurrence Record Digital Data Set.
OR/WA BLM. [February 2015]. wpr_geobob_fauna_obs_point.
Pilsbry, H. A. 1925. The family Lancidae distinguished from the Ancylidae. The
Nautilus 38(3): 73-75.
Roth, B. 2015. personal communication with Emilie Blevins.
Smith, D. G. 2001. Pennak's Freshwater Invertebrates of the United States:
Porifera to Crustacea , 4 th ed. New York: John Wiley & Sons. 638 pp.
Tryon, G. W. 1865. Descriptions of new species of North American
Lymnaeidae. American Journal of Conchology 1(3): 223-231, pl. 22, figs. 14-17, pl. 23.
Turgeon, D. D., J. F. Quinn, Jr., A. E. Bogan, E. V. Coan, F. G. Hochberg, W.
G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth,
A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams. 1998.
Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2 nd ed. American Fisheries Society Special Publication
26 , Bethesda, Maryland. 526 pp.
USGS. Nonindigenous Aquatic Species Database. Accessed 3/5/2015.
Available at: http://nas.er.usgs.gov/default.aspx
ATTACHMENT 2: List of pertinent or knowledgeable contacts
Ed Johannes, Deixis Consultants
Tom Burke, retired
Barry Roth, independent consultant
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ATTACHMENT 3: Map of species’ occurrence in Oregon
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ATTACHMENT 4: Photographs of this species
Photos of this species are available online at the Academy of Natural Sciences of Drexel University (ANSP) online collections database
( http://clade.ansp.org/malacology/collections/wip/galleryzoom.php?img=021/
21961_Ancylus_subrotundatus_api.jpg
).
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ATTACHMENT 5: Aquatic Gastropod Survey Protocol, including specifics for this species
Taxonomic group:
Aquatic Gastropoda
How:
Please refer to the following documents for detailed mollusk survey methodology:
1. General collection and monitoring methods for aquatic mollusks (pages 64-
71):
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. Contract #43-0E00-4-
9112. 274 pp. plus appendices.
2. Standard survey methodology that can be used by field personnel to determine presence/absence of aquatic mollusk species in a given waterbody, and to document species locations and habitats in a consistent format:
Duncan, N. 2008. Survey Protocol for Aquatic Mollusk Species:
Preliminary Inventory and Presence/Absence Sampling. Version 3.1.
Portland, OR. Interagency Special Status/Sensitive Species Program.
U.S. Department of Interior, Bureau of Land Management,
Oregon/Washington and U.S. Department of Agriculture, Forest Service,
Region 6. 52 pp. [Available at: http://www.fs.fed.us/r6/sfpnw/issssp/species-index/faunainvertebrates.shtml].
Species-specific survey details, including:
1.
Identification features
2.
Historic and current distribution
3.
Federal Units where species is suspected or documented
4.
Areas where surveys are recommended
5.
Habitat where surveys should take place
6.
Commonly associated mollusk species
7.
General survey method and instructions (e.g. time of year)
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Lanx subrotunda
This species has been observed on cobble, boulder, or bedrock substrate in cold, fast-flowing creeks and large rivers in the Umpqua, Rogue, and Klamath basins of southwestern Oregon. Any creeks or rivers in these drainages with appropriate habitat could support populations of this species. Surveys are recommended in reaches where land or aquatic management actions may impact this species and at known sites to evaluate current population status.
Populations appear to be patchy, but both recent and historical abundance estimates for this species range from rare to common and abundant when found.
This species is documented on the Roseburg District BLM and suspected on the Coos Bay District BLM and Medford District BLM. This species is also documented on the Umpqua National Forest and Fremont-Winema National
Forest. It is suspected on the Rogue-Siskiyou National Forest, and may occur on the Siuslaw National Forest.
Additional surveys in the Rogue and Klamath basins, particularly in the Rogue-
Siskiyou National Forest and Fremont-Winema National Forest, would provide better understanding of this species’ current distribution, as some records are historical and others greatly extend the range for this species. Henderson
(1936) reported that observers had recorded this species in abundance in sympatry with Lanx alta in the Rogue River, Grants Pass, but Frest and
Johannes (2005) suggest populations in the Rogue Basin need additional scrutiny to determine if they should be assigned to Lanx alta or Lanx subrotunda . Lanx alta has also been reported on the Fremont-Winema National
Forest, but lanx specimens collected in 2010 and identified in 2011 as L. subrotunda have shells whose height is too low to be L. alta (Roth, personal communication). Surveys in all basins should take care to note these differences in shell height and size ( L. subrotunda is also smaller than L. alta ).
In general, this species can be identified by its large (length 10-12mm) and flat shell. It has a complete circumferential muscle scar, easily distinguishing species in this family from other freshwater limpets (Burch 1989; Frest and
Johannes 2000). Shell height is about half that of the shell width, and twothirds of shell length. The shell is pigmented reddish-brown or cinnamon in color, rarely with white streaks, and older specimens may have a yellowish color at the periphery (Frest and Johannes 2000). Tryon (1865) described the shell as oval, nearly round and fragile.
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Surveys for this species have been conducted in spring (March), summer (July,
August), and fall (September, October, November). Because this species inhabits swift-flowing water, often in deeper channels, surveys for this species may be technically difficult or unsafe in periods of high water or flow.
Generally, surveys could be conducted from late August to early October, but conditions may vary seasonally and depend on recent weather events. Caution should be taken when conditions are sub-optimal. Dip net and hand collection are two common collection methods for this species. Duncan (2006) employed inner tubes with masks, snorkels and wetsuits to survey for mollusks. Shells or whole animals can be observed or collected for identification. Commonly cooccurring species include Juga silicula shastaensis , Fluminicola species nov.
,
Physella lordi , Margaritifera falcata , Corbicula fluminea , and Gonidea angulata
(Frest and Johannes 2000; Duncan 2006).
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