The spelling Toxolasma lividus formerly followed Turgeon et al. (1998). When the genus name Toxolasma was proposed by Rafinesque (1831), he did not designate a gender nor was it clear from the species included in the genus. A recent review of Toxolasma (Lee 2006) determined the gender is neuter and endings of four species have changed: Toxolasma lividus to lividum; Toxolasma parvus to parvum; Toxolasma paulus to paulum; and Toxolasma texasensis to texasense. Through misinterpretations of species identities and synonomy, Toxolasma has been considered to contain two to eight species (e.g., Johnson 1970, Burch 1975, Turgeon et al. 1988, Turgeon et al. 1998). Examination of museum vouchers indicate that there may be as many as fifteen species. These recent publications have been little more than species lists and present no explanation for the synonomies. The last such work to do so was Ortmann and Walker (1922) which mistakenly synonymized Toxolasma lividus under Carunculina moesta (Lea, 1841). In recent works, C. moesta has been interpreted as a junior synonym of Carunculina glans (Lea, 1834). However, Pilsbry and Rhoads (1896), Ortmann (1918), and Ortmann and Walker (1922) indicate that lividus and glans are not the same shell and probably represent different species. Williams et al. (2008), however, noted that there appears to be little evidence to support recognition of two subspecies.

The species is now considered likely to be a synonym of Toxolasma glans, although this still requires verification (J. Cordeiro pers. comm. 2011). As such, we follow the current taxonomic standing of Toxolasma lividium for the purpose of this assessment, until further taxonomic work suggests otherwise.

A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).

Toxolasma lividum has been assessed as Least Concern due to its wide distribution and the fact that populations are thought to 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.

This species is found in the United States of America and is known from the Ohio River Basin west of Pennsylvannia, including Ohio, Michigan, Illinois, Indiana and Kentucky (Parmalee and Bogan 1998). It is found in the Tennessee and Cumberland River drainages in Tennessee, Virginia and Kentucky, whilst also being present in the Arkansas River in Arkansas and Oklahoma (Parmalee and Bogan 1998). The main population is found in the Missouri/Arkansa area. It has a large extent of occurrence in excess of 400,000 km².

As this is a small mussel, it has been suggested that this species may be more widespread than thought, and requires more extensive and intensive investigations, including headwater lakes (Cummings and Berlocher 1990). It also is able to survive in some overbank habitats, as well as tributaries and tailwaters of dams, implying this species is not immediately imperiled (Williams et al. 2008).

Population trends: numbers and occurrences continue to decline in the Cumberlandian region (LeGrand et al. 2006, Bogan 2002, Jones et al. 2006). It is listed as endangered in the north part of its range in Indiana, Kentucky, Michigan, Ohio and is considered rare in Illinois and Missouri. The species is probably extirpated from North Carolina (LeGrand et al. 2006, Bogan 2002), and Georgia (H Athearn, shell collection at the North Carolina State Museum of Natural Sciences) and near extirpated from Virginia (Jones et al. 2006). In the remainder of its range it is secure (northern Arkansas, southern Missouri) (NatureServe 2010).

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).

It has been estimated that the introduction of the Zebra Mussel, Dreissena polymorpha, into the Mississippi River basin has increased the extinction rates of native freshwater mussels from 1.2% of species per decade to 12% per decade (Roe 2002). Native mussels have shown differential sensitivity to Dreissena polymorpha infestations, but as this species tends to be found in small to medium sized rivers, this may reduce its risk of colonization by D. polymorpha (Roe 2002).

Organic pollution, siltation from agriculure and clearcutting, channel alteration and inundation, acid mine run off from coalmines as well as the Zebra Mussel may threaten this species (Roe 2002), although as discussed above the Zebra Mussel may only represent a minor threat to this species. However, as this species has been found in impoundments, it seems unlikely that sedimentation has a immediate severe impact on its survival; the effect of pollution is unknown (Roe 2002).

This species is not utilized.

This species does not appear to occur in protected areas. There are no major threats affecting this species severely throughout its range, although NatureServe has given this species a status of G3 and the American Fisheries Society a Vulnerable Status (NatureServe 2009). Monitoring and continued surveys of known populations is recommended, and surveys to determine the impact from threat processes, as declines have been observed in parts of this species' range.