Toxolasma lividum - Rafinesque, 1831
Purple Lilliput
Synonym(s): Carunculina glans (I. Lea, 1831) ;Carunculina lividus (Rafinesque, 1831)
Taxonomic Status: Accepted
Related ITIS Name(s): Toxolasma lividus (Rafinesque, 1831) (TSN 80362)
Unique Identifier: ELEMENT_GLOBAL.2.119668
Element Code: IMBIV43030
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Toxolasma
Genus Size: C - Small genus (6-20 species)
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Concept Reference
Concept Reference: Turgeon, D.D., J.F. Quinn, Jr., A.E. Bogan, E.V. Coan, F.G. Hochberg, W.G. Lyons, P.M. Mikkelsen, R.J. Neves, C.F.E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F.G. Thompson, M. Vecchione, and J.D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland: 526 pp.
Concept Reference Code: B98TUR01EHUS
Name Used in Concept Reference: Toxolasma lividus
Taxonomic Comments: 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 review of Toxolasma (Lee, 2006) determined the gender is neuter and endings of four species changed: Toxolasma lividus to lividum; Toxolasma parvus to parvum; Toxolasma paulus to paulum; and Toxolasma texasensis to texasense. These changes are adopted by Williams et al. (2017).

Turgeon et al. (1998) recognized eight species. Recent evidence supports no changes at the genus level, but species boundaries within Toxolasma remain uncertain and undescribed species have yet to be formerly described (Williams et al. 2017).
Conservation Status

NatureServe Status

Global Status: G3Q
Global Status Last Reviewed: 19Dec2011
Global Status Last Changed: 19May2009
Rounded Global Status: G3 - Vulnerable
Reasons: Now believed to be the same species as Toxolasma glans, the species has a considerably wider, although still sporadic, distribution with relatively low densities at many sites.
Nation: United States
National Status: N3 (19May2009)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S2), Arkansas (S2), Georgia (SH), Illinois (S1), Indiana (S2), Kentucky (S1), Michigan (S1), Missouri (S1), North Carolina (SX), Ohio (S1), Oklahoma (SH), Tennessee (S1S2), Virginia (SH)

Other Statuses

IUCN Red List Category: LC - Least concern
American Fisheries Society Status: Special Concern (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: 20,000-200,000 square km (about 8000-80,000 square miles)
Range Extent Comments: 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 North Carolina and eastern Tennessee downstream to the 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).

Area of Occupancy: 2,501 to >12,500 4-km2 grid cells
Area of Occupancy Comments:  

Number of Occurrences: 21 - 80
Number of Occurrences Comments: It is in Indiana in Graham Creek (Harmon, 1989) and can still be found in Wabash River tributaries in Indiana (Fisher, 2006). In Illinois, it is now restricted to the Little Wabash and Vermilion Rivers where it is sporadic but was formerly known from the Embarras River and Wabash River tributaries and Wabash River (Cummings and Mayer, 1997). It is also known from the Clinton River drainage in Michigan (Strayer, 1980). In Missouri, it is known only in southern Missouri in a few sites (Oesch, 1995). In Arkansas, it is known from the Ouachita River system in South Fourche La Fave River, Poteau River, Illinois River but always in low population numbers (Harris and Gordon, 1997); also historically in the Cache River (Christian et al., 2005) and above Lake Sequoyah (Gordon, 1982). Historically it was in the Poteau River and tributaries, Arkansas/Oklahoma (Vaughn and Spooner, 2004). Branson (1984) suggested it might occur in Oklahoma based on close proximity in southern Arkansas and Missouri, but could document no occurrences. Harris (1994) found the species in the uppermost reaches of the Poteau River in Arkansas close to the Oklahoma border and a subsequent survey of the same river further downstream in Oklahoma did not yield any specimens (Vaughn and Spooner, 2004). In the Cumberland River basin, it is known to occur sporadically in less than ten tributary streams (e.g., Little South Fork Cumberland River, Buck Creek: see Schuster et al., 1989). In Tennessee, it was found throughout the upper Tennessee River system, including the Powell, Clinch, Emory, Holston, French Broad, Tellico, Little Pigeon, and Little Rivers, as well as the main channel of the Tennessee River below Knoxville. It was also found in the Duck and Elk Rivers and occurred in the Caney Fork, Stones and Harpeth Rivers and numerous tributaries of the Cumberland River system in Tennessee (Parmalee and Bogan, 1998). In Alabama, it is extant in several reaches of the Tennessee River and impounded lower reaches of tributaries and remains in some free-flowing tributary reaches (Williams et al., 2008). Although it once occurred just over the border in the Clinch River in Virginia, it does not appear to reach as far northeast as West Virginia. A recent study of the North Fork Holston River in Virginia (Jones and Neves, 2007) did not find this species and is likely extirpated there or is extremely rare. It was recently collected in the Middle Fork North Branch Vermillion River in Illinois and Jordan Creek in Indiana (Szafoni et al., 2000). In Indiana, Harmon (1989) reported it from seven of 12 sites surveyed in Graham Creek in the southeast portion of the state; as well as from Sugar Creek (east fork White River drainage) in central Indiana (Harmon, 1992) (most weathered shells but some living and fresh dead) and Tippecanoe River (Cummings and Berlocher, 1990). It can still be found in Wabash River tributaries in Indiana (Fisher, 2006). In Ohio it is nearly extirpated (Watters, 1995) occurring in a few sites in the Maumee drainage in headwater lakes of the St. Joseph River (Grabarkiewicz and Crail, 2006), Fish Creek, Blanchard River but not recently exc. in Michigan St. Joseph (Watters et al., 2009). In Kentucky, it is sporadic in the Green River and upper Cumberland River below Cumberland Falls (Cicerello and Schuster, 2003). There is a record from Lookout Creek in Georgia (H. Athearn Collection).

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Because the species is no longer believed to be restricted as a Cumberlandian endemic with the lividum form separate and distinct from the glans form, the species is not as rare and even more widely scattered through the region than previously thought; extending into the Tennessee River drainage from southwestern Virginia, western North Carolina and eastern Tennessee downstream to the mouth of the Tennessee River (Williams et al., 2008).

Number of Occurrences with Good Viability/Integrity: Very few to few (1-12)
Viability/Integrity Comments: Barr et al. (1994) determined (based on 1981 survey data) that viable populations exist in the Paint Rock River.

Overall Threat Impact: High
Overall Threat Impact Comments: It is impacted by chemical and organic pollution, siltation from agriculture and clear-cutting, channel alteration and inundation, and acid coal mine run-off. Cattle wading in small streams have destroyed considerable habitat formerly used by this species. Roe (2002) lists the following threats: invasion of competetive zebra mussels (limited threat due to habitat preference), siltation, pollution (agricultural, domestic, industrial) (effect unclear on this species), dams and impoundments (although this species adapts better to impoundments than others).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Numbers and occurrences have, and continue to, declined drastically since 1979 in the Cumberlandian region. This species is listed as endangered in Illinois, Kentucky, Michigan and Ohio and is also considered rare in Indiana and Missouri. The species is extirpated in North Carolina in the French Broad River where it formerly occurred (LeGrand et al., 2006). In Virginia it is likely extirpated from the North Fork Holston (Jones and Neves, 2006) and Clinch Rivers (VA NHP, pers. comm., 2007). Outside the Cumberlandian region it is secure, however, although it has a fairly wide range, it is considered to occur only sporadically within the range.

Long-term Trend: Decline of 30-50%
Long-term Trend Comments: In North Carolina, it was recorded from Hot Springs on the French Broad River, Madison Co. but Johnson (1970) suggested these specimens may be Villosa vanuxemensis (Bogan, 2002). Branson (1984) postulated on the occurrence of this species (as Toxolasma glans) in Oklahoma based on presence in the Spring and Elk Rivers in nearby Missouri, but today no evidence of the species can be found. It is nearly extirpated from Ohio with possibly a single extant population left in the St. Joseph River (Watters et al., 2009).

Intrinsic Vulnerability: Unknown
Intrinsic Vulnerability Comments: Sensitive to pollution, siltation, habitat perturbation, inundation, and loss of glochidial hosts.

Environmental Specificity: Narrow to moderate.
Environmental Specificity Comments: Although the T. lividus has been found in lotic environments it is more typically found in clean, swiftly flowing water.

Other NatureServe Conservation Status Information

Inventory Needs: Determine extent of existing populations, continue surveys, and assess potential reintroduction sites.

Protection Needs: All populations should receive protection through acquisition, easement, registry, and working with local, state, and federal government agencies on issues relating to development, water quality, river designation, etc. Watershed management with particular emphasis on control of acid coal mine run-off and agricultural induced siltation is critical.

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 North Carolina and eastern Tennessee downstream to the 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).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States AL, AR, GA, IL, IN, KY, MI, MO, NCextirpated, OH, OK, TN, VA

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
AL Colbert (01033), Franklin (01059)*, Jackson (01071), Lauderdale (01077), Lawrence (01079)*, Limestone (01083), Madison (01089), Marshall (01095)
AR Arkansas (05001)*, Ashley (05003), Benton (05007), Bradley (05011), Calhoun (05013), Clark (05019), Cleburne (05023), Cleveland (05025), Conway (05029), Craighead (05031), Crawford (05033), Crittenden (05035), Dallas (05039), Desha (05041)*, Faulkner (05045), Fulton (05049), Grant (05053), Greene (05055), Hot Spring (05059), Howard (05061), Izard (05065), Jackson (05067), Johnson (05071), Lawrence (05075), Madison (05087), Marion (05089), Mississippi (05093), Montgomery (05097), Nevada (05099), Newton (05101), Ouachita (05103), Perry (05105), Pike (05109), Poinsett (05111), Polk (05113), Pope (05115), Randolph (05121), Saline (05125), Scott (05127), Searcy (05129), Sevier (05133), Sharp (05135), Stone (05137), Van Buren (05141), Washington (05143), White (05145), Woodruff (05147)
IL Douglas (17041), Pope (17151), Vermilion (17183), White (17193)
IN Adams (18001)*, Allen (18003), Bartholomew (18005), Benton (18007), Boone (18011), Carroll (18015), Cass (18017), Clinton (18023), De Kalb (18033), Decatur (18031), Delaware (18035), Fountain (18045), Fulton (18049), Grant (18053), Hamilton (18057), Hancock (18059), Henry (18065)*, Howard (18067), Huntington (18069), Jay (18075), Jefferson (18077), Jennings (18079), Kosciusko (18085), Lawrence (18093), Madison (18095), Marion (18097), Marshall (18099), Martin (18101), Miami (18103), Montgomery (18107), Noble (18113), Parke (18121)*, Posey (18129)*, Pulaski (18131), Putnam (18133)*, Randolph (18135), Rush (18139), Shelby (18145), Starke (18149), Tippecanoe (18157), Vermillion (18165)*, Wabash (18169), Warren (18171), Wells (18179), White (18181), Whitley (18183)
KY Adair (21001), Allen (21003)*, Butler (21031)*, Casey (21045)*, Cumberland (21057), Green (21087), Jackson (21109), Laurel (21125), Lincoln (21137), Logan (21141), McCracken (21145), McCreary (21147)*, Muhlenberg (21177)*, Ohio (21183)*, Pendleton (21191)*, Pulaski (21199), Rockcastle (21203), Russell (21207)*, Shelby (21211)*, Spencer (21215)*, Todd (21219)*, Warren (21227)*, Wayne (21231)*
MI Hillsdale (26059), Monroe (26115)*, Oakland (26125), Tuscola (26157)*
MO Barry (29009), Barton (29011), Bollinger (29017), Butler (29023), Christian (29043), Douglas (29067), Greene (29077), Jasper (29097), Madison (29123), McDonald (29119), Newton (29145), Oregon (29149), Ripley (29181), Shannon (29203), St. Francois (29187), Stone (29209), Taney (29213), Wayne (29223), Webster (29225)
OH Allen (39003), Hancock (39063), Putnam (39137), Warren (39165)*, Williams (39171)
TN Franklin (47051), Giles (47055)*, Grundy (47061), Humphreys (47085), Marshall (47117), Maury (47119), Monroe (47123), Rutherford (47149)*
VA Russell (51167)*, Scott (51169)*, Smyth (51173)*, Washington (51191)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
04 Cass (04080205)+*, Lake Huron (04080300)*, Lake St. Clair (04090002), Clinton (04090003)+, Ottawa-Stony (04100001)*, Raisin (04100002)+, St. Joseph (04100003)+, Upper Maumee (04100005)+, Auglaize (04100007)+, Blanchard (04100008)+, Lower Maumee (04100009)*
05 Little Miami (05090202)+, Licking (05100101)+*, Upper Green (05110001)+, Barren (05110002)+*, Middle Green (05110003)+, Upper Wabash (05120101)+, Salamonie (05120102)+, Mississinewa (05120103)+, Eel (05120104)+, Middle Wabash-Deer (05120105)+, Tippecanoe (05120106)+, Wildcat (05120107)+, Middle Wabash-Little Vermilion (05120108)+, Vermilion (05120109)+, Sugar (05120110)+, Middle Wabash-Busseron (05120111)*, Embarras (05120112)+, Lower Wabash (05120113)+, Little Wabash (05120114)+, Upper White (05120201)+, Driftwood (05120204)+, Flatrock-Haw (05120205)+, Upper East Fork White (05120206)+, Muscatatuck (05120207)+, Lower East Fork White (05120208)+, Upper Cumberland (05130101), Rockcastle (05130102)+, Upper Cumberland-Lake Cumberland (05130103)+, South Fork Cumberland (05130104)+, Upper Cumberland-Cordell Hull (05130106)*, Caney (05130108)*, Stones (05130203)*, Harpeth (05130204)+*, Red (05130206)+, Salt (05140102)+*, Lower Ohio-Bay (05140203)+, Lower Ohio (05140206)
06 North Fork Holston (06010101)+*, Holston (06010104)*, Upper French Broad (06010105)*, Pigeon (06010106)*, Lower French Broad (06010107)*, Nolichucky (06010108)*, Watts Bar Lake (06010201)*, Lower Little Tennessee (06010204)+, Upper Clinch (06010205)+, Powell (06010206)*, Emory (06010208)*, Middle Tennessee-Chickamauga (06020001)*, Guntersville Lake (06030001), Wheeler Lake (06030002)+, Upper Elk (06030003)+, Lower Elk (06030004)+, Pickwick Lake (06030005)+, Bear (06030006)+, Upper Duck (06040002)+, Buffalo (06040004)+, Lower Tennessee (06040006)+
07 Whitewater (07140107)+
08 Upper St. Francis (08020202)+, Lower St. Francis (08020203)+, Little River Ditches (08020204)+, Cache (08020302)+, Lower White (08020303)+*, Ouachita Headwaters (08040101)+, Upper Ouachita (08040102)+, Little Missouri (08040103)+, Lower Ouachita-Smackover (08040201)+, Upper Saline (08040203)+, Lower Saline (08040204)+
11 Beaver Reservoir (11010001)+, James (11010002)+, Bull Shoals Lake (11010003)+, Middle White (11010004), Buffalo (11010005)+, North Fork White (11010006)+, Upper Black (11010007), Current (11010008)+, Lower Black (11010009)+, Spring (11010010)+, Eleven Point (11010011)+, Strawberry (11010012)+, Upper White-Village (11010013)+, Little Red (11010014)+, Spring (11070207)+, Elk (11070208)+, Illinois (11110103)+, Poteau (11110105)+, Frog-Mulberry (11110201)+, Dardanelle Reservoir (11110202)+, Lake Conway-Point Remove (11110203)+, Cadron (11110205)+, Fourche La Fave (11110206)+, Lower Arkansas-Maumelle (11110207), Mountain Fork (11140108)+, Lower Little (11140109)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
U.S. Distribution by Watershed (based on multiple information sources) Help
Ecology & Life History
Basic Description: A freshwater mussel
General Description: Shell small, solid, relatively heavy for size, thinner posteriorly, elliptical to ovate-elliptical or subrhombodial, inflated; anterior margin evenly rounded; ventral margin flatly convex; posterior margin bluntly pointed to vaguely biangulate, point near posterio-ventral junction with a slightly convex margin obliquely sloped towards dorsum in males, point supermedial to midline with truncated margin sloping anterio-ventrally to a sharply rounded junction with ventral margin, posterior margin rounded in young shells; dorsal margin flatly convex to almost straight posteriorly, slightly convex anteriorly; anterio-dorsal junction may be smooth to slightly angular; beaks well developed, rather full, moderately elevated above dorsal margin, sculpted by relatively heavy concentric ridges; posterior ridge subangulate and elevated near beaks to low and flattened posteriorly, double, termini at posterior point; posterior point concave, a radial swelling from the beak to the posterio-ventral junction may be present in females; periostracum rather rough, greenish to olive-brown or black, subshiny, may be obscurely rayed with minute lines. Pseudocardinal teeth rather small, heavy, subcompressed to triangular, elevated, serrated, double in left valve, posterior tooth taller than anterior tooth, single in right valve, triangular, small lamellae may develop anterior and posterior to contiguous sulci; interdentum very short, relatively narrow; lateral teeth relatively long, slightly curved to straight; anterior muscle scars small, distinct, impressed; pallial line not impressed; posterior muscle scars lightly impressed, confluent; beak cavity moderately developed but not deep; nacre purple, leadened or bluish in shell cavity, may be paler along periphery of shell, nacre rarely white, iridescent posteriorly.
Diagnostic Characteristics: 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.
Reproduction Comments: This species generally has been considered a long-term brooder. Graved females ahve been reported from May until July. However, indicative of these records, Hoeh (personal communication) has found some Michigan populations to function as short-termed brooders and to produce multiple broods per year. Glochidia are held in echtobranchous marsupia. Hill (1986) determined Lepomis cyanellus (green sunfish) and Lepomis megalotis (longear sunfish) to serve as glochidial hosts.
Ecology Comments: No specific studies have considered this species. Densities estimate were presented in Jenkinson (1988).
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Mobility and Migration Comments: This species is probably rather sessile with only limited movement through the substrate. Passive downstream movement may occur when mussels are displaced from the substrate during floods. Major dispersal occurs when glochidia are encysted on their hosts.
Riverine Habitat(s): CREEK, High gradient, Low gradient, MEDIUM RIVER, Riffle
Special Habitat Factors: Benthic
Habitat 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).
Adult Food Habits: Detritivore
Immature Food Habits: Parasitic
Food Comments: Larvae (glochidia) of freshwater mussels generally are parasitic on fish and display varying degrees of host specificity. No specific tropic studies have been conducted on this species. General literature claims that mussels are filter-feeders which remove phytoplankton from the water column. These assumptions appear to be based on casual observations of mussels in situ and a few examinations of rectal contents. Baker (1928) speculated that detritus was the primary energy source. This has been substantiated by James (1987) and correlates well with microhabitats observed in the field. This suggests that mussels may occupy a variety of guilds such as postulated for the Sphaeriidae (see Lopez and Layzer, 1989).
Phenology Comments: Little is known concerning the phenology of mussels other than when eggs/glochidia are held in the branchial marsupia. Being poikilotherms, activity levels would expectly be greatly reduced during cold-temperature months.
Length: 5.1 centimeters
Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: 1) Maintain high quality T. LIVIDUS habitat, consisting of riffle areas of streams with good water quality. 2) Monitor and regulate land use upstream to prevent siltation of streams. 3) Physical modifications to streams such as dredging and impoundment should be avoided, as should biological modifications to natural fish communities in areas where the species may occur.
Restoration Potential: Upgrading of water quality undoubtedly will help in the recovery of the species. Dredging for sand and gravel as well as channel modifications in good mussel habitats should be halted, as well as any management schemes which would alter the natural fish population, particularly sunfish.
Preserve Selection & Design Considerations: Streams or tributaries with good water quality would probably make the best preserve areas for the species. Acquisition of land on either side of a creek would help ensure that pollutant/siltation runoff to the stream would be minimal, although land use practices should be monitored in the entire watershed to minimize siltation.
Management Requirements: Requirements include the maintenance of flowing water in riffle areas with suitable water quality. Stream modifications such as dredging and impoundment should be avoided, as well as any modifications to the natural fish communities in areas where the species may occur.

Construction, mining, and agricultural activities in stream watersheds should be closely monitored in order to minimize siltation and acid runoff to streams. Point sources should be closely checked to insure compliance with discharge permit regulations.

Monitoring Requirements: Because T. LIVIDUS is most often reported from shallow water habitats, wading and hand picking specimens from the substrate is probably the most effective sampling method. Care must be taken to thoroughly search the substrate, since the species is relatively small and could easily be overlooked.
Management Research Needs: Determine specific ecological requirements of the mussel (including water flow requirements, sediment preferences, effects of temperature and food quality on growth rates, etc.) as well as the effects of particular pollutants.
Biological Research Needs: Determine habitat preferences and environmental tolerances, tolerances to various pollutants and siltation, and reproductive biology/glochidial hosts. Determine systematic relationship between the nominal forms LIVIDUS (Cumberland River drainage), MAESTUM (Tennessee River drainage), and GLANS (portions of Ohio and Mississippi river systems).
Population/Occurrence Delineation
Group Name: Freshwater Mussels

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on some evidence of historical or current presence of single or multiple specimens, including live specimens or recently dead shells (i.e., soft tissue still attached and/or nacre still glossy and iridescent without signs of external weathering or staining), at a given location with potentially recurring existence. Weathered shells constitute a historic occurrence. Evidence is derived from reliable published observation or collection data; unpublished, though documented (i.e. government or agency reports, web sites, etc.) observation or collection data; or museum specimen information.
Mapping Guidance: Based on the separation distances outlined herein, for freshwater mussels in STANDING WATER (or backwater areas of flowing water such as oxbows and sloughs), all standing water bodies with either (1) greater than 2 km linear distance of unsuitable habitat between (i.e. lotic connections), or (2) more than 10 km of apparently unoccupied though suitable habitat (including lentic shoreline, linear distance across water bodies, and lentic water bodies with proper lotic connections), are considered separate element occurrences. Only the largest standing water bodies (with 20 km linear shoreline or greater) may have greater than one element occurrence within each. Multiple collection or observation locations in one lake, for example, would only constitute multiple occurrences in the largest lakes, and only then if there was some likelihood that unsurveyed areas between collections did not contain the element.

For freshwater mussels in FLOWING WATER conditions, occurrences are separated by a distance of more than 2 stream km of unsuitable habitat, or a distance of more than 10 stream km of apparently unoccupied though suitable habitat. Standing water between occurrences is considered suitable habitat when calculating separation distance for flowing water mussel species unless dispersal barriers (see Separation Barriers) are in place.

Several mussel species in North America occur in both standing and flowing water (see Specs Notes). Calculation of separation distance and determination of separation barriers for these taxa should take into account the environment in which the element was collected. Juvenile mussels do not follow this pattern and juveniles are typically missed by most standard sampling methods (Hastie and Cosgrove, 2002; Neves and Widlak, 1987), therefore juvenile movement is not considered when calculating separation distance.

Separation Barriers: Separation barriers within standing water bodies are based solely on separation distance (see Separation Distance-suitable, below). Separation barriers between standing water bodies and within flowing water systems include lack of lotic connections, natural barriers such as upland habitat, absence of appropriate species specific fish hosts, water depth greater than 10 meters (Cvancara, 1972; Moyle and Bacon, 1969) or anthropogenic barriers to water flow such as dams or other impoundments and high waterfalls.
Separation Distance for Unsuitable Habitat: 2 km
Separation Distance for Suitable Habitat: 10 km
Alternate Separation Procedure: None
Separation Justification: Adult freshwater mussels are largely sedentary spending their entire lives very near to the place where they first successfully settled (Coker et al., 1921; Watters, 1992). Strayer (1999) demonstrated in field trials that mussels in streams occur chiefly in flow refuges, or relatively stable areas that displayed little movement of particles during flood events. Flow refuges conceivably allow relatively immobile mussels to remain in the same general location throughout their entire lives. Movement occurs with the impetus of some stimulus (nearby water disturbance, physical removal from the water such as during collection, exposure conditions during low water, seasonal temperature change or associated diurnal cycles) and during spawning. Movement is confined to either vertical movement burrowing deeper into sediments though rarely completely beneath the surface, or horizontal movement in a distinct path often away from the area of stimulus. Vertical movement is generally seasonal with rapid descent into the sediment in autumn and gradual reappearance at the surface during spring (Amyot and Downing, 1991; 1997). Horizontal movement is generally on the order of a few meters at most and is associated with day length and during times of spawning (Amyot and Downing, 1997). Such locomotion plays little, if any, part in the distribution of freshwater mussels as these limited movements are not dispersal mechanisms. Dispersal patterns are largely speculative but have been attributed to stream size and surface geology (Strayer, 1983; Strayer and Ralley, 1993; van der Schalie, 1938), utilization of flow refuges during flood stages (Strayer, 1999), and patterns of host fish distribution during spawning periods (Haag and Warren, 1998; Watters, 1992). Lee and DeAngelis (1997) modeled the dispersal of freshwater into unoccupied habitats as a traveling wave front with a velocity ranging from 0.87 to 2.47 km/year (depending on mussel life span) with increase in glochidial attachment rate to fish having no effect on wave velocity.

Nearly all mussels require a host or hosts during the parasitic larval portion of their life cycle. Hosts are usually fish, but a few exceptional species utilize amphibians as hosts (Van Snik Gray et al., 2002; Howard, 1915) or may metamorphose without a host (Allen, 1924; Barfield et al., 1998; Lefevre and Curtis, 1911; 1912). Haag and Warren (1998) found that densities of host generalist mussels (using a variety of hosts from many different families) and displaying host specialists (using a small number of hosts usually in the same family but mussel females have behavioral modifications to attract hosts to the gravid female) were independent of the densities of their hosts. Densities of non-displaying host specialist mussels (using a small number of hosts usually in the same family but without host-attracting behavior) were correlated positively with densities of their hosts. Upstream dispersal of host fish for non-displaying host specialist mussels could, theoretically, transport mussel larvae (glochidia) over long distances through unsuitable habitat, but it is unlikely that this occurs very often. D. Strayer (personal communication) suggested a distance of at least 10 km, but a greater distance between occurrences may be necessary to constitute genetic separation of populations. As such, separation distance is based on a set, though arbitrary, distance between two known points of occurrence.

Date: 18Oct2004
Author: Cordeiro, J.
Notes: Contact Jay Cordeiro ( for a complete list of freshwater mussel taxa sorted by flow regime.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 19Dec2011
NatureServe Conservation Status Factors Author: Cordeiro, J. (2011); Gordon, M. (1992); Whittaker, J. C. (1994)
Management Information Edition Date: 01Aug1986
Management Information Edition Author: DIANE LAURITSEN
Element Ecology & Life History Edition Date: 19Dec2011
Element Ecology & Life History Author(s): Cordeiro, J. (2011); GORDON, M. E. (1991)

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