SPECIES FACT SHEET
Common Name: Newcomb’s littorine snail (or Newcomb Periwinkle)
Scientific Name: Littorina subrotunda - (Carpenter, 1864) - Newcomb
Periwinkle
Other Related Name(s): Algamorda subrotundata; Paludinella newcombiana
Hemphill 1876
Related ITIS Name(s): Algamorda newcombiana (Hempill, 1876) (TSN 70475)
Phylum:
Class:
Order:
Family:
Mollusca
Gastropoda
Neotaenioglossa
Littorinidae
OR/WA BLM and FS Region 6 Units where Suspected or Documented:
Both the Forest Service and BLM have listed the Newcomb’s littorine snail or
Newcomb Periwinkle as a Sensitive Species in Oregon.
The Newcomb’s littorine snail or Newcomb Periwinkle has been documented on
one BLM District (CB) and is suspected to occur on one National Forest (SIU) in
Oregon .
Status:
Natural Heritage Program Rank and Status:
 Oregon State Rank: S1; critically imperiled
List 1 - Threatened or endangered throughout range
 Washington State Rank: S1; critically imperiled*
 National Rank: N2; vulnerable to extirpation or extinction
 Global Rank: G5; secure
State Status:
 Oregon State Status: None
 Washington State Status: C - candidate animal; under review for listing
Federal Status:
 SOC: Species of Concern
*New information from Washington indicates the species may be more common
than previously thought; this rank is expected to change soon. (Fleckenstein,
2009)
Technical Description:
Newcomb’s littorine snail is a medium-small marine Prosobranch snail with a
thin, conical shell with four or five rounded whorls; operculum present; one
pair of tentacles. The shell is smooth, pale in color; sometimes with irregular
blotches (Hemphill 1877). The apex is sub-acute, last whorl somewhat
inflated, subrimate, with or without three or four longitudinal brown bands;
aperture ovate, outer lip thin, inner lip appressed to the columella and
somewhat thickened; suture deep; epidermis greenish; operculum with nucleus
subcentral with two and one-half whorls (Hemphill 1877). It is one centimeter
in length (NatureServe 2009).
Figure 1. Photo of Algamorda newcombiana by Nancy Duncan; used with permission.
Life History:
The biology and ecology of Newcomb's littorine snail are incompletely
understood (Larsen et al., 1995).
Range, Distribution, and Abundance:
This cold-water North Pacific marine gastropod has a southernmost limit in
North America in Humboldt Bay, California; but occurs from there north to the
Gulf of Alaska. In the U.S. it has been documented in scattered locations along
the coast of Washington, Oregon, and northern California (NatureServe 2009).
Known sites include the north spit of Coos Bay and Siletz Bay in Oregon; Neah
Bay, Mukkaw Bay, Grays Harbor and Willapa Bay in Washington, and
Humboldt Bay in California (Jones 1977; Larsen et al., 1995).
The current distribution and status of Newcomb's littorine snail is uncertain.
Its current range is apparently more extensive and secure in Washington than
in Oregon or California, the only other states in which it is found. The species
is currently known from only two or three Washington areas and is now more
localized in most of those areas than in the past (Larsen et al., 1995).
Figure 2. Washington locations where Newcomb's littorine snail, Algamorda subrotundata, has been
reported (Larsen et al., 1995)
Habitat Associations:
Newcomb's littorine snail is found within coastal environments, clinging to
rocky shores. It inhabits a narrow zone of intertidal habitat on
glasswort/pickleweed (Salicornia virginica) salt marshes at the edges of bays
and estuaries where fresh and ocean waters mix (Hinde 1954). It resides above
the mean high tide where it is inundated occasionally but infrequently (Hinde
1954, MacDonald 1969, Taylor 1981).
Its optimal distribution within its ecosystem is at, or slightly above, mean high
tide so that it is submerged in sea water only a few hours per year (NatureServe
2009). Talmadge (1962) reported that L. newcombiana, "...is neither a
freshwater nor a true marine gastropod." MacDonald (1969) found it more
abundant in less brackish environments. Though tolerant of both fresh and
salt water, Newcomb's littorine snail will climb out of either when immersed,
and will drown if forced to remain submerged (Larsen et al., 1995).
This snail lives on the stems of Salicornia, and possibly other marsh plants. It
also lives on substrate such as woody debris and rocks beneath vegetation,
where it remains moist and protected from the sun and wind. It feeds on
microscopic and macroscopic algae and the vascular plants on and under
which it lives (Larsen et al., 1995). It presumably feeds on Salicornia vegetation
by rasping the surfaces to remove small particles for digestion (NatureServe
2009). Newcomb’s littorine snail is present year round with possible decreased
activity in winter (NatureServe 2009).
Figure 3. Habitat for Algamorda newcombiana in Coos Bay, Oregon.
Photo by Nancy Duncan; used with permission.
Figure 4. Salicornia (pickleweed) microhabitat. Photo by Nancy Duncan; used with permission.
Threats:
Major threats to Newcomb's littorine snail are habitat loss, pollution, and
invasive species.
Habitat loss and pollution are primary threats to this species. Habitat in
Oregon and California has been threatened by development and pollution, and
may be similarly threatened in Washington. Populations and habitats are
destroyed as suitable salt marshes are developed or used as dumps for fill,
spoils, or waste (Larsen et al., 1995). By 1961, the population in Humboldt
Bay in California was nearly extirpated due to habitat loss caused by the
dumping and burning of sawdust (Keen 1970).
The notice of review (USFWS 1977) concluded: “although recovering after
closure of several sawmills, habitat around Humboldt Bay is still threatened by
filling and dumping; in Coos Bay, Oregon, it is threatened by log storage on the
mud flats, filling and dredging, and the effluent of treated sawdust chips which
goes into the bay; in Grays Harbor, Washington, it is potentially threatened by
oil spill, pulp mill waste, and municipal waste”.
Another threat to the saltmarsh habitat of this species is the invasion and
spread of cordgrass (Spartina spp.), a potential threat to the snail's habitat
throughout its range. This large introduced grass is of concern due to its
ability to displace native plants, degrade wildlife habitat, and alter the
geomorphology of estuaries. This exotic plant is out-competing and destroying
several native biotic communities (Larsen et al., 1995). Thought to live
predominantly on Salicornia in Willapa Bay’s native saltmarsh, Newcomb’s
littorine snail may already be experiencing habitat loss as a result of Spartinia
alternaflora crowding out native vegetation (Species Account 2008). The ability
of Spartina to convert Salicornia salt marshes may be the greatest threat to
Newcomb's littorine snails.
Conservation Considerations: (Larsen et al., 1995)
 Monitor and assess activities for impacts on Newcomb's littorine snails
and associated habitat. Activities include construction, industrial and
municipal uses, recreation, the storage and transport of toxic substances,
forest practices, and agriculture.

The use of insecticides or herbicides may negatively affect this species. If
insecticide or herbicide use is planned for areas where this species
occurs, utilize available resources that may be helpful when assessing the
use of pesticides and any alternatives.

The greatest challenge is to protect its habitat from further destruction
and to restore it wherever opportunities are presented.
Management Recommendations: (Larsen et al., 1995)

Survey and map all Newcomb's littorine snail occurrences.

Consider this species in shoreline management or development permits.

Monitor the effects of habitat changes on colonies of this species,
including grazing and irrigation; insecticide, herbicide, and fertilizer
application. Avoid using chemicals where salt marsh habitats might be
affected.

If insecticide or herbicide use is planned for areas where this species
occurs, refer to Appendix A (page A-1) for contacts helpful when
evaluating pesticides and their alternatives.

Avoid placing fill on habitats; avoid use of treated woods unless shown to
have no impact.

Avoid off-road vehicle activities that may compact, rut, or otherwise alter
the soil, moisture, or vegetative regime on salt marsh habitats.

If a spill jeopardizes a significant portion of the state's Newcomb's littorine
snail population, collect individuals from threatened areas, along with
enough vegetation and substrate to support them. These animals can
then be moved to the nearest unoccupied (or underpopulated) area of
safe, suitable habitat, or temporarily maintained in captivity until they
can be returned to restored habitat.

Assess the potential effects of toxic spill cleanup methods and their
alternatives, on Newcomb's littorine snails.

Assess Forest Practices permit applications for impacts to the Newcomb's
littorine snail and its habitat.

Avoid introducing exotic plants and animals into areas inhabited by
Newcomb's littorine snails.
Preparer:
Theresa Stone
Umpqua National Forest
02 September 2009
Edited by:
Rob Huff
FS/BLM Conservation Planning Coordinator
January 2010
References:
Fleckenstein, John. Washington Natural Heritage Program, Zoologist. Personal
Communication, 2009.
Hemphill, Henry. 1877. Description of a new California mollusk. Proc. Cal.
Acad. Sci. Series 1, Vol 7(1):49. (Lib. note: actual date of publication may be
1876).
Hinde, H. P. 1954. The vertical distribution of salt marsh phanerogams in
relation to tide levels. Ecol. Monogr. 24(2):209-225.
Jones, M. P. (ED.) 1977. 41 Taxa snails, fish, crustaceans proposed.
Endangered Species Tech. Bull 11 (2): 1-5.
Keen, A.M. 1970. Western land mollusks. American Malacological Symposium.
"Rare and Endangered Mollusks." Malacologia 10(1):51-53.
Larsen, E.M., E. Rodrick, and R. Milner. 1995. Management Recommendations
for Washingtons Priority Species. Volume I: Invertebrates. Washington
Department of Wildlife. Olympia, Washington.
MacDonald, K. B. 1969. Molluscan faunas of Pacific Coast salt marshes and
tidal creeks. The Veliger 11(4):399-405.
NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web
application]. Version 7.1. NatureServe, Arlington, Virginia. Available
http://www.natureserve.org/explorer.
Talmadge, R. R. 1962. Random notes on Littorina newcombiana Hemphill.
Ann. Rep. Amer. Malacol. Union (Pac. Div. 15th Ann. Meeting) (Bull. 29):29.
[Abst].
Taylor, D.W. 1981. Freshwater mollusks of California: a distributional
checklist. Calif. Fish and Game 67(3):140-163.
United States Fish and Wildlife Service. 1977. Proposed endangered or
threatened status for 41 U.S. species of fauna. Federal Reg. 42(8): 2507-2512
(1/12/77).