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  3. Toxolasma lividus

Toxolasma lividus

Diagnostic description 2

Several species that occur within the Cumberlandian region may be confused with TOXOLASMA LIVIDUM. TOXOLASMA PARVUM does not get as big or as high, has a thinner shell, always has a white nacre which mat be somewhat silvery due to the iridescense (LIVIDUM when white is more of a porcelain white, similar to the nacre of VILLOSA TRABALIS [Conrad, 1834]), and always exibits female shell morphology (it's a hermaphroditic species). TOXOLASMA is more elliptically shaped, being not as tall, has a yellowish periostracum, and has a paler nacre which often has a yellowish overcast. VILLOSA VANUXEMII (Lea, 1838) tends to be taller; has a very shiny nacre which may be salmon or purple (often with reddish overtones) with a brownish cast in the shell cavity; the posterior margin of the female is acutely truncated and often exibits an indentation just below the posterior point; may have some wavy, greenish capillary rays across a brown periostracum; and has a rounded posterior ridge. If LIVIDUM and GLANS are conspecific, T. PARVUM and VILLOSA LIENOSA (Conrad, 1834) are probably the only species which might be mistaken for "LIVIDUM". Height: 28mm.

Distribution 3

Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Toxolasma lividum occurs in the lower Ohio River drainage from southwestern Ohio downstream to near the mouth of the Ohio River (Cummings and Meyer, 1992). It occurs west of the Mississippi River in southern Missouri (Oesch, 1995), northern Arkansas (Harris and Gordon, 1990), potentially into Oklahoma, and possibly eastern Kansas. It is widespread, but sporadic, in the Cumberland River drainage downstream of Cumberland Falls (Cicerello et al., 1991; Parmalee and Bogan, 1998) and in most of the Tennessee River drainage from southwestern Virginia, western orth Carolina and eastern Tennessee downstream to teh mouth of the Tennessee River (Neves, 1991; Parmalee and Bogan, 1998) including across northern Alabama in the Tennessee River and some tributaries (Williams et al., 2008).

Habitat 4

Habitat Type: Freshwater

Comments: This species can inhabit fine-particle substrates and also sand, gravel, or cobbles and boulders in riffles or flats immediatly above riffles (Gordon, 1989). This species is reported from the headwaters of small to medium sized rivers. They have been collected from various substrates including sand, mud, and gravel. Like other members of this genus Toxolasma lividus seems to adapt to lentic environments as many have been found in the Wheeler Reservoir in the Tennessee River Drainage (Roe, 2002). It is often the first species encountered in headwater areas. It generally occurs at depths < 1 m. It very rarely is encountered in a big river habitat or reservoirs (Gordon and Lazer, 1989).

Habitat and ecology 5

Habitat and Ecology

This species inhabits headwaters of rivers, lakes and reservoirs (J. Cordeiro pers. comm. 2010).This small species inhabits all sizes of rivers, from slow to swift currents, in mud, sand and gravel substrates or shallow, rocky gravel points and sandbars (Cummings and Berlocher 1990, Parmalee and Bogan 1998, Williams et al. 2008). The Green Sunfish Lepomis cyanellus and Longear Sunfish Lepomis megalotis are hosts fish for the glochidia of this species (Parmalee and Bogan 1998).

Systems
  • Freshwater

Iucn red list assessment 6


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
Cordeiro, J.

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

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

Justification
Toxolasma lividum has been assessed as Least Concern due to its wide distribution and the fact that populations arethoughtto be stable in large parts of its range. However, declines have been observed in other parts, such as the Cumberlandian region, and it is classed as threatened in certain northern range states (Indiana, Kentucky, Michigan, Ohio; it is also rare in Illinois and Missouri). Surveys and monitoring need to be undertaken to keep a check on population declines and ensure that these are not followed by further declines which may warrant a higher threat category in the future.

Morphology 7

The purple lilliput is up to 2.5 cm (1 inch) long , is elongate to oblong and moderately inflated. The   anterior end is rounded and the posterior end is bluntly pointed in males or truncated in females. The dorsal margin is nearly straight and the ventral margin is straight.

Umbos are broad and raised slightly above the hinge line. The beak sculpture has three or four heavy concentric bars.

The periostracum (outer shell layer) is smooth except for growth lines. Color is tan to brown, and black in older individuals.

On the inner shell, the   left valve has two erect, triangular and serrated   pseudocardinal teeth. The two lateral teeth are straight, elevated and striated. The right valve has one large, elongate and roughened pseudocardinal tooth. Anterior to this tooth is a smaller (lamellar) tooth. The beak cavity is shallow to moderately deep. The nacre is purple and iridescent posteriorly.

In Michigan, this species can be confused with the lilliput. The lilliput has a white nacre and is more elongate and cylindrical.

Range length: 2.5 (high) cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes shaped differently

Sources and Credits

  1. (c) rkkessler, all rights reserved
  2. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28913973
  3. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28913967
  4. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28913977
  5. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34760518
  6. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34760515
  7. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31427493

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