Species Profile

Threaded Vertigo

Scientific Name: Nearctula sp.
Taxonomy Group: Molluscs
Range: British Columbia
Last COSEWIC Assessment: April 2010
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern


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Quick Links: | Description | Habitat | Biology | Threats | Protection | National Recovery Program | Documents

Image of Threaded Vertigo

Description

The Threaded Vertigo is a minute land snail with a high, rather cylindrical shell. The shell is about 2.4–3.3 mm high, dull, dark brown, and somewhat coarsely marked with fine, parallel growth lines. Within the opening of the adult shell, there are four white denticles (tooth–like protuberances); the immature shell lacks denticles. The Threaded Vertigo is currently without a formal scientific name due to its convoluted nomenclatural history, but the validity of the species is not in question. (Updated 2017/05/25)

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Distribution and Population

The global range of the species extends from southwestern British Columbia through western Washington State and Oregon to west–central California. In Canada, the species occurs on southern Vancouver Island, Saturna Island, and the Sunshine Coast on mainland British Columbia. There are 24 recent (since 1984) distribution records. On Vancouver Island, clusters of sites occur within the Capital Regional District (Victoria area), but the species is known from only scattered sites along the east coast, northward to just south of Courtenay. In the Strait of Georgia, the species is known from one site on Saturna Island. On the Sunshine Coast (B.C. mainland), it occurs at several places between Gibsons and Egmont. (Updated 2017/05/25)

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Habitat

In British Columbia, the snails occur in moist deciduous and mixed–wood forests at low elevations, usually below 200 m. They are often associated with Bigleaf Maples and an understory of ferns and shrubs characteristic of moist, rich sites. Older riparian forests containing groves of large maples appear to be particularly suitable. The snails are largely arboreal and encountered most frequently on trunks of maples, where they occur within crevices of grooved bark or moss mats. They are occasionally found on other deciduous trees, on fern fronds, or on the ground within the leaf litter. The snails have a patchy distribution both within and among forest stands, and aggregations occur on some trees while others are devoid of snails. (Updated 2017/05/25)

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Biology

Little is known about the biology of the Threaded Vertigo, and hence information has to be extrapolated from similar, related species. Like most land snails, the Threaded Vertigo is hermaphroditic (possesses both male and female reproductive organs), but the extent of cross–fertilization is not known. In similar species, eggs are laid singly. The lifespan is probably short, two years or less. The snails hibernate in winter and probably aestivate during dry periods in summer. Movements and active dispersal are limited, but passive transport on falling leaves during windstorms is plausible. The snails have been found in small groves of trees near roadsides and busy recreational trails, suggesting that they can tolerate some habitat disturbance, provided suitable moist microhabitats remain available. (Updated 2017/05/25)

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Threats

The distribution of the species coincides with densely populated and highly modified parts of British Columbia. Much of the land conversion is historical in these lowland coastal areas, but human developments continue to encroach on remaining natural areas concomitant with an expanding population. Housing developments, road building and other associated infrastructure, agriculture, and forestry are shrinking and fragmenting habitats. Most records for this species are from parks or federal lands protected from land conversion, but potential habitats on private lands throughout most of the species’ range continue to diminish. Populations in protected areas are not necessarily secure due to habitat degradation from intensive recreational or other uses, and invasion by introduced plants and animals. (Updated 2017/05/25)

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Protection

Federal Protection

More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.

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Documents

PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

10 record(s) found.

COSEWIC Status Reports

  • COSEWIC Assessment and Status Report on the Threaded Vertigo Nearctula sp. in Canada (2010)

    The Threaded Vertigo is a minute land snail with a high, rather cylindrical shell. The shell is about 2.4–3.3 mm high, dull, dark brown, and somewhat coarsely marked with fine, parallel growth lines. Within the opening of the adult shell, there are four white denticles (tooth-like protuberances); the immature shell lacks denticles. The Threaded Vertigo is currently without a formal scientific name due to its convoluted nomenclatural history, but the validity of the species is not in question.

COSEWIC Assessments

  • COSEWIC Assessment Summary and Status Report: Threaded Vertigo Nearctula sp. (2010)

    Assessment Summary – April 2010 Common nameThreaded Vertigo Scientific nameNearctula sp. StatusSpecial Concern Reason for designationThis minute terrestrial snail species is at the northern extent of its range, and found in lowland areas around the Strait of Georgia and on southern Vancouver Island. Most individuals live on the bark of Bigleaf Maple trees and appear to have poor capacity for dispersal between trees and sites. Removal of trees and habitat degradation due to urban expansion, roads and associated infrastructure, forestry, and agriculture are the main threats. Occurrence British Columbia Status historyDesignated Special Concern in April 2010.

Response Statements

  • Response Statement - Threaded Vertigo (2010)

    This minute terrestrial snail species is at the northern extent of its range, and found in lowland areas around the Strait of Georgia and on southern Vancouver Island. Most individuals live on the bark of Bigleaf Maple trees and appear to have poor capacity for dispersal between trees and sites. Removal of trees and habitat degradation due to urban expansion, roads and associated infrastructure, forestry, and agriculture are the main threats.

Action Plans

  • Multi-species Action Plan for Gulf Islands National Park Reserve of Canada (2017)

    The Multi-species Action Plan for Gulf Islands National Park Reserve of Canada applies to lands and waters occurring within the boundaries of Gulf Islands National Park Reserve (GINPR). The plan meets the requirements for action plans set out in the Species at Risk Act (SARA (s.47)) for species requiring an action plan that regularly occur at this site. Measures described in this plan will also provide benefits to other species of conservation concern that regularly occur at GINPR.

Management Plans

  • Management Plan for the Threaded Vertigo (Nearctula sp.) in Canada [Proposed] (2017)

    The Minister of Environment and Climate Change is the competent minister under SARA for the Threaded Vertigo and has prepared the federal component of this management plan (Part 1), as per section 65 of SARA. To the extent possible, it has been prepared in cooperation with the Province of British Columbia, as per section 66(1) of SARA. SARA section 69 allows the Minister to adopt all or part of an existing plan for the species if the Minister is of the opinion that an existing plan relating to wildlife species includes adequate measures for the conservation of the species. The Province of British Columbia provided the attached management plan for the Threaded Vertigo (Part 2) as science advice to the jurisdictions responsible for managing the species in British Columbia. It was prepared in cooperation with Environment and Climate Change Canada.

Orders

  • Order Acknowledging Receipt of the Assessments Done Pursuant to Subsection 23(1) of the Act (2011)

    His Excellency the Governor General in Council, on the recommendation of the Minister of the Environment, hereby acknowledges receipt, on the making of this Order, of assessments conducted under subsection 23(1) of the Species at Risk Act by the Committee on the Status of Endangered Wildlife in Canada with respect to the species set out in the annexed schedule.
  • Order Amending Schedule 1 to the Species at Risk Act (2012)

    The purpose of the Order Amending Schedule 1 to the Species at Risk Act is to add 18 species to Schedule 1, the List of Wildlife Species at Risk (the List), and to reclassify 7 listed species, pursuant to subsection 27(1) of SARA. This amendment is made on the recommendation of the Minister of the Environment based on scientific assessments by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and on consultations with governments, Aboriginal peoples, stakeholders and the Canadian public.

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2010 (2010)

    Under Canada’s Species At Risk Act (SARA), the foremost function of COSEWIC is to “assess the status of each wildlife species considered by COSEWIC to be at risk and, as part of the assessment, identify existing and potential threats to the species”. During the past year, COSEWIC held two Wildlife Species Assessment Meetings and reviewed the status of 79 wildlife species (species, subspecies, populations). During the meeting of November 2009, COSEWIC assessed or reviewed the classification of the status of 28 wildlife species. COSEWIC assessed or reviewed the classification of an additional 51 wildlife species (species, subspecies and populations) during their April 2010 meeting. For species already found on Schedule 1 of SARA, the classification of 32 species was reviewed by COSEWIC and the status of the wildlife species was confirmed to be in the same category (extirpated - no longer found in the wild in Canada but occurring elsewhere, endangered, threatened or of special concern). The wildlife species assessment results for the 2009-2010 reporting period include the following: Extirpated: 6 Endangered: 39 Threatened: 16 Special Concern: 17 Data Deficient: 1 This report transmits to the Minister the status of 46 species newly classified as extirpated, endangered, threatened or of special concern, fulfilling COSEWIC’s obligations under SARA Section 24 and 25. A full detailed summary of the assessment for each species and the reason for the designation can be found in Appendix I of the attached report. Since its inception, COSEWIC has assessed 602 wildlife species in various risk categories, including 262 Endangered, 151 Threatened, 166 Special Concern and 23 Extirpated. In addition, 13 wildlife species have been assessed as Extinct. Also, to date, 46 wildlife species have been identified by COSEWIC as Data Deficient and 166 wildlife species were assessed as Not at Risk. This year has been a particularly productive year for COSEWIC’s Aboriginal Traditional Knowledge (ATK) Subcommittee. In April 2010 COSEWIC approved the Aboriginal Traditional Knowledge Process and Protocol Guidelines, providing clear and agreed principles for the gathering of Aboriginal Traditional Knowledge to carry out COSEWIC functions as required under Section 15(2) of SARA (See Appendix III of the attached report). We are grateful for the rich and enthusiastic contribution made by community elders and experts in helping the ATK Subcommittee prepare the ATK protocols.

Consultation Documents

  • Consultation on Amending the List of Species under the Species at Risk Act: Terrestrial Species – November 2010 (2010)

    As part of its strategy for protecting wildlife species at risk, the Government of Canada proclaimed the Species at Risk Act (SARA) on June 5, 2003. Attached to the Act is Schedule 1, the list of the species that receive protection under SARA, also called the List of Wildlife Species at Risk. Please submit your comments by February 4, 2011 for species undergoing normal consultations and by February 4, 2012 for species undergoing extended consultations.

Recovery Document Posting Plans

  • Environment and Climate Change Canada's Three-Year Recovery Document Posting Plan (2016)

    Environment and Climate Change Canada’s Three-Year Recovery Document Posting Plan identifies the species for which recovery documents will be posted each fiscal year starting in 2014-2015. Posting this three year plan on the Species at Risk Public Registry is intended to provide transparency to partners, stakeholders, and the public about Environment and Climate Change Canada’s plan to develop and post these proposed recovery strategies and management plans. However, both the number of documents and the particular species that are posted in a given year may change slightly due to a variety of circumstances. Last update March 31, 2017