Species Profile


Scientific Name: Toxolasma parvum
Taxonomy Group: Molluscs
Range: Ontario
Last COSEWIC Assessment: May 2013
Last COSEWIC Designation: Endangered
SARA Status: No schedule, No Status

Individuals of this species may be protected under Schedule 1 under another name; for more information see Schedule 1, the A-Z Species List, or if applicable, the Related Species table below.

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Quick Links: | Photo | Description | Habitat | Biology | Threats | Protection | Other Protection or Status | National Recovery Program | Documents

Image of Lilliput

Lilliput Photo 1



The Lilliput (Toxolasma parvum) is one of Canada’s 54 freshwater mussel species. It is a rare and small mussel, typically less than 4 centimeters and occasionally reaching sizes of 5.5 centimeters in length. It is the only mussel of the genus Toxolasma found in Canada and can be recognized by the following features: Thick shell that is elliptical to oval in shape; dull, smooth and cloth-like outer shell; front (anterior) end is rounded and the back (posterior) end is rounded on males, squared on females; shell colour is brown to brownish-black and may have green rays on the dorsal slope; inside of shell (nacre) is shiny and silvery-white or bluish-white; raised part at the top of the shell (beak) is sculptured with 4–6 heavy concentric ridges, and is slightly raised above the hinge line; and hinge teeth are fully developed, but compressed (thin serrated pseudocardinal teeth and long, thin and straight lateral teeth).


Distribution and Population

Lilliput is only found in North America, where it is widely distributed from the Gulf of Mexico to the Great Lakes basin. In Canada, Lilliput was historically found in southern Ontario in the drainages of lakes St. Clair, Erie and Ontario. No longer found in over 40 percent of its historical range, Lilliput is now restricted to the Sydenham River, lower Thames River (Baptiste Creek), Ruscom River, Belle River, Grand River, Welland River, Jordan Harbour and Hamilton Harbour (Sunfish Pond, Cootes Paradise and Grindstone Creek). In the United States, Lilliput can still found in 22 states, but is considered possibly extirpated from Georgia and New York, critically imperiled in Pennsylvania, endangered in Michigan, and vulnerable in Indiana and Wisconsin.



Lilliput is found in a variety of habitats, from small to large rivers to wetlands and the shallows of lakes, ponds and reservoirs. It prefers to burrow in soft substrates (river and lake bottoms) made of mud, sand, silt or fine gravel.



Lilliput has a short lifespan, living to a maximum age of 12 years. It can be hermaphroditic (each mussel features both male and female gonads). Spawning occurs from June to August and glochidia (mussel larvae) are released in July of the following year. Like most other freshwater mussels, the glochidia are parasitic on fishes. In this case, adult mussels lure in a fish with worm-like filaments on their shells and release mucous packages of glochidia disguised as food. When the fish takes a bite, the package ruptures, releasing the glochidia to attach to their host as they flow through its gills. Here they will remain until they reach their juvenile, free-living stage and drop off to burrow in the substrate below. Adult Lilliput essentially stays in one location (i.e., sessile), and may move only a few metres along the substrate the entire rest of its life. The likely host fishes for this mussel in Canada are the Johnny Darter (Etheostoma nigrum), Green Sunfish (Lepomis cyanellus) and Bluegill (Lepomis macrochirus). Like all species of freshwater mussels, Lilliput filters its food from the water. Bacteria and algae are its primary food sources.



Serious threats facing remaining Lilliput include habitat loss and the increasing pollution of the waters where they live and feed. Municipal, agricultural and industrial activities can result in higher levels of sediment, nutrients and contaminants that clog mussel gills, disrupt breathing, movement and reproduction, and degrade habitat quality. Other possible threats include habitat destruction, and even mussel removal, by riverbed dredging for transportation and shipping purposes, as well as continued residential and commercial development and dam construction along Lilliput habitat. Invasive Zebra and Quagga mussels can colonize on the Lilliput in large numbers, restricting their feeding, breathing, moving and reproduction. The invasive Round Goby may also out-compete the Lilliput for prey, as well as competing with its host fishes.



Federal Protection

In Canada, this species is currently under consideration for listing as Endangered under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available online at AquaticSpeciesAtRisk.ca or on the SARA Registry at SaraRegistry.gc.ca.

Provincial and Territorial Protection

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


Other Protection or Status

Several mussel species are protected under Canada’s Species at Risk Act and the Ontario Endangered Species Act, 2007 including: Round Hickorynut, Kidneyshell, Northern Riffleshell, Snuffbox, Round Pigtoe, Salamander Mussel, Rayed Bean and Wavy-rayed Lampmussel. The Lilliput may therefore, benefit indirectly from protection afforded to these species or by actions implemented (e.g., research, stewardship and outreach) under the direction of the above recovery strategies. Additionally, the collection of freshwater mussels requires a collection permit issued by the Ontario Ministry of Natural Resources under authority of the Fish and Wildlife Conservation Act.



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.

4 record(s) found.

COSEWIC Status Reports

Response Statements

  • Response Statement - Lilliput (2013)

    This species has a fairly restricted range in Canada, confined to tributaries of Lake St. Clair, Lake Erie, and Lake Ontario. Populations once found in the open Canadian waters of Lake St. Clair, Lake Erie and the Detroit River have disappeared. Overall, the species has lost 40% of its former range in Canada. The invasion of freshwater habitat by the exotic Zebra and Quagga mussels, combined with pollution from urban development and sedimentation are the main cause of populations disappearing and the range shrinking.

COSEWIC Annual Reports

  • COSEWIC Annual Report – 2012-2013 (2013)

    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”. COSEWIC held two Wildlife Species Assessment Meetings in this reporting year (October, 2012 to September 2013) from November 25 to November 30, 2012 and from April 28 to May 3, 2013. During the current reporting period, COSEWIC assessed the status or reviewed the classification of 73 wildlife species. The wildlife species assessment results for the 2012-2013 reporting period include the following: Extinct: 0 Extirpated: 2 Endangered: 28 Threatened: 19 Special Concern: 19 Data Deficient: 4 Not at Risk: 1 Total: 73 Of the 73 wildlife species examined, COSEWIC reviewed the classification of 50 species that had been previously assessed. The review of classification for 26 of those species resulted in a confirmation of the same status as the previous assessment.

Consultation Documents

  • Lilliput - Consultations on listing under the Species at Risk Act (2014)

    The Lilliput has recently been assessed as “Endangered” by the Committee on the Status of Endangered Wildlife in Canada. Before deciding whether this species will be protected under the Species at Risk Act, Fisheries and Oceans Canada would like your opinion, comments and suggestions regarding the possible ecological, cultural and economic impacts of listing or not listing it.