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Toxolasma parvus

Distribution 2

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) This species ranges throughout the Mississippian Region; Great Lakes into western New York state, west to Minnesota, southern Canada; Peninsular Florida; Apalachicolan region; western Gulf Coastal region in most drainages in Louisiana to the Rio Grande system in Texas (Johnson, 1999).

Geographic range 3

The lilliput is found throughout the Mississippi drainage, in the St. Lawrence drainage and Gulf of Mexico drainages. In general its range includes southern Manitoba south to Texas, east to Mississippi, north to western New York and throughout Michigan and southern Ontario to Minnesota.

In Michigan the lilliput was mainly found in the Raisin and Huron Rivers and tributaries and Lake Erie. It was also historically recorded from the Black River in the west side of the state.

Biogeographic Regions: nearctic (Native )

Habitat and ecology 4

Habitat and Ecology

This species inhabits lotic mud-bottomed streams and rivers (White and White 1977). It also occurs in rain-fed swamps and shallow ponds, as well as larger systems such as the Great Lakes (New York State Department of EnvironmentalConservation 2005). According to White and White (1977) the species prefers areas protected from wave action over silt or soft loam.

There is evidence to suggest that the species has increased in abundance following human modification of previously unsuitable habitat, for example impoundment of lentic water systems (White and White 1977). It can also inhabit canals (Smith et al. 2002).

Systems
  • Freshwater

Iucn red list assessment 5


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
Cummings, K. & Cordeiro, J.

Reviewer/s
Bohm, M., Seddon, M. & Collen, B.

Contributor/s
Dyer, E., Soulsby, A.-M., Whitton, F., Kasthala, G., McGuinness, S., De Silva, R., Milligan, HT, Herdson, R., Thorley, J., McMillan, K., Collins, A., Duncan, C., Offord, S. & Richman, N.

Justification
Toxolasma parvumhas been assessed as Least Concern as it is widespread throughout the eastern half of the US (recorded in 24 states) and extends into Ontario and Manitoba in Canada. Although no specific population estimates are available, this species is considered Least Concern due to it being locally abundant and because of its ability to withstand human modification of habitats (e.g. impoundment).

Morphology 6

The lilliput is up to 3.8 cm (1.5 inches) long, is elliptical and cylindrical and fairly solid . The   anterior end and posterior ends are rounded. The dorsal margin is straight and the ventral margin is fairly straight.

Umbos are broad, low, and slightly elevated above the hinge line. The beak sculpture has five or six course concentric ridges.

The periostracum (outer shell layer) is fairly smooth except for growth lines. Color is dark green or brown, turning black in older specimens.

On the inner shell, the   left valve has two erect, divergent, triangular   pseudocardinal teeth. The two lateral teeth are slightly curved, rough, and moderately long. The right valve has one erect, grooved, triangular pseudocardinal tooth. Anterior to this tooth is a smaller (lamellar) tooth.

The beak cavity is shallow to moderately deep. The nacre is bluish-white and iridescent.

In Michigan, this species can be confused with the purple lilliput. The purple lilliput has a purple nacre and is more rounded and compressed.

Range length: 3.8 (high) cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes shaped differently

Nature serve conservation status 7

Rounded Global Status Rank: G5 - Secure

Reasons: This species is widespread throughout the Mississippian Region to southern Canada. Although considered stable throughout much of its range, it is rare in Canada (only a few records from Ontario remain), but has recently expanded its range in the south and southeastern U.S.

Intrinsic Vulnerability: Unknown

Environmental Specificity: Broad. Generalist or community with all key requirements common.

Comments: This species is found typically in the shallows of lakes, ponds, and reservoirs, as well as in small to large rivers, where it lives in mud, sand, or fine gravel (Parmalee and Bogan, 1998).

Sources and Credits

  1. (c) Femorale, some rights reserved (CC BY-NC), http://www.femorale.com/shellphotos/detail.asp?species=Toxolasma%20parvus%20(Barnes,%201823)
  2. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28914003
  3. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/25067417
  4. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34760525
  5. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34760522
  6. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31427508
  7. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28913997

More Info

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(c) NatureServe, some rights reserved (CC-BY-NC)

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