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Pleuronaia barnesiana

(I. Lea, 1838)

Tennessee Pigtoe

G2Imperiled (G2G3) Found in 17 roadless areas NatureServe Explorer →
G2ImperiledGlobal Rank
Least concernIUCN
Very high - mediumThreat Impact
Tennessee pigtoe (Pleuronaia barnesiana). Photo by U.S. Fish & Wildlife Service, Public Domain (U.S. Government Work), via ECOS.
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.107814
Element CodeIMBIV17020
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryInvertebrate Animal
IUCNLeast concern
Endemicendemic to a single nation
KingdomAnimalia
PhylumMollusca
ClassBivalvia
OrderUnionoida
FamilyUnionidae
GenusPleuronaia
Synonyms
Fusconaia barnesiana(I. Lea, 1838)Pleurobema meredithii(I. Lea, 1858)
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.
Taxonomic Comments
This species can exhibit considerable ecophenotypic variation depending on stream size. Ortmann (1918) distinguished three morphs relative to the inflation of the shell: bigsbyensis Lea, 1841, a compressed form from small creeks and small rivers: barnesiana s.s., an intermediately inflated shell from medium-sized rivers; and tumescens Lea, 1845, an inflated morph from large river habitats. In that the degree of inflation varied clinally with the increasing size of the river, subspecific status is not warranted for this species although in the past some authors have found it convenient to designate the degree of inflatedness with these names in a varietal context but in the nomenclatural form of a subspecies. Interestingly, both the tumescens and barnesiana morphs have been recorded from Muscle Shoals suggesting that microhabitat may influence the degree of inflation rather than river size alone. In an unpublished study of molecular systematics, Campbell and Harris (2006) found high genetic distance from other Fusconaia species. Pleuronaia barnesiana has historically been treated as a member of the genus Fusconaia despite differences from other members of the genus (Ortmann, 1917; 1918). Preliminary genetic analyses suggest it is more closely related to Pleuronaia dolabelloides than to species of Fusconaia (Campbell et al., 2005; Bogan et al., unpublished). Bogan et al. (unpublished) found Lexingtonia subplana is synonymous with Fusconaia masoni and since L. subplana is the type species for the genus, Lexingtonia becomes a synonym of Fusconaia. The next available generic name for barnesiana and dolabelloides is Pleuronaia Frierson, 1927. This is supported by Campbell and Lydeard (2012). Pleurobema gibberum was also found to belong to the Pleuronaia clade (see Williams et al., 2008). This is supported by Campbell and Lydeard (2012).
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2023-12-07
Change Date1996-11-25
Edition Date2023-12-06
Edition AuthorsGordon, M.E. (1992); Cordeiro, J. (2011); T. Cornelisse (2023)
Threat ImpactVery high - medium
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences21 - 80
Rank Reasons
This species has a moderate range but due to long and short-term population declines and many ongoing threats, it has few viable occurrences.
Range Extent Comments
This species occurs in the Tennessee River System in Virginia, Tennessee, North Carolina, Mississippi, Alabama, and Georgia, USA (USFWS 2020; GBIF 2023).
Occurrences Comments
This species is found in 43-63 watersheds, considered populations by the USFWS (USFWS 2020; USFWS 2023).
Threat Impact Comments
This species is threatened by sedimentation, nutrient, and chemical pollution from land conversion activities, including development, agriculture, oil and gas operations, and coal mining, dams and water diversions that change hydrologic conditions, host fish distribution, and prevent habitat connectivity and recolonization, and changes in precipitation (USFWS 2020; USFWS 2023).
Ecology & Habitat

Description

Shells elliptical, subquadrate to subtriangular, solid to thick, compressed to inflated; anterior margin rounded; ventral margin flat to slightly curved; posterior flatly curved with a blunt to biangulate point at the posterio-ventral junction, obliquely sloped; dorsal margin nearly straight to curved, anterior dorsal junction may appear angular; beaks positioned subcentrally to the anterior 25% of shell length, low to considerably elevated, sculpted with a few bars parallel to lines of growth; posterior ridge apparent, rounded to slightly angular, may appear double; periostracum yellowish to dark brown, often with numerous fine to moderately-wide dark green rays, raying usually absent from posterior slope. Pseudocardinal teeth moderate to fairly large, may be somewhat compressed, double in left valve, single in right but may develop an auxilliary dentical anteriorly; interdentum short, moderately wide; lateral teeth fairly large, straight to slightly curved, double in left valve, single in right; anterior muscle scars distinct, moderately deep; posterior muscle scars impressed; pallial line impressed; beak cavity shallow, somewhat angular; nacre white to pinkish, iridescent.

Diagnostic Characteristics

The extant morphs of this species can be easily confused with the Pleurobema oviforme (Conrad, 1834). Anatomically they are rather distinct to the tetrabranchous marsupia of Fusconaia vs the ectobranch marsupia of Plerobema oviforme shells tend to be more elliptically shaped or triangular in appearance, have a rounded posterior slope, and have a yellowish to greenish yellow periostracum often with a relatively wide green ray subcentrally. Creek to small river morphs of oviforme tend to be rayless white barnesiana morphs from similar habitats often are highly rayed and rays do not form blotches.

Habitat

This species is found in riffles, runs, and shoals, and moderate to high gradient streams of small to medium-sized rivers with stable substrates of coarse sand, gravel, and/or cobble (USFWS 2020).

Reproduction

This species is a short-term brooder (USFWS 2020).
Other Nations (1)
United StatesN2
ProvinceRankNative
TennesseeS2Yes
AlabamaS1Yes
VirginiaS2Yes
MississippiS1Yes
GeorgiaS1Yes
North CarolinaS1Yes
Threat Assessments
ThreatScopeSeverityTiming
7 - Natural system modificationsLarge - restrictedSerious - moderateHigh (continuing)
7.2 - Dams & water management/useLarge - restrictedSerious - moderateHigh (continuing)
9 - PollutionPervasive - largeSerious - moderateHigh (continuing)
9.2 - Industrial & military effluentsRestricted (11-30%)Serious - moderateHigh (continuing)
9.3 - Agricultural & forestry effluentsLarge (31-70%)Serious - moderateHigh (continuing)
9.3.1 - Nutrient loadsLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
9.3.2 - Soil erosion, sedimentationLarge - restrictedSerious - moderateHigh (continuing)
11 - Climate change & severe weatherRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
11.1 - Habitat shifting & alterationRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)

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Roadless Areas (17)
Idaho (1)
AreaForestAcres
Bear CreekCaribou-Targhee National Forest118,582
North Carolina (3)
AreaForestAcres
Bald MountainPisgah National Forest11,085
Wesser BaldNantahala National Forest4,061
Yellowhammer Branch (add.)Nantahala National Forest1,255
Tennessee (6)
AreaForestAcres
Bald MountainCherokee National Forest11,743
Brushy RidgeCherokee National Forest7,469
Joyce Kilmer Slickrock Add.Cherokee National Forest1,396
Little Frog Addition NECherokee National Forest321
Little Frog Addition NWCherokee National Forest628
Upper Bald RiverCherokee National Forest9,202
Virginia (7)
AreaForestAcres
Bear CreekJefferson National Forest18,274
Beartown Addition AJefferson National Forest1,370
Beartown Addition BJefferson National Forest2,985
Garden MountainJefferson National Forest3,960
Hunting Camp Little Wolf CreekJefferson National Forest8,953
Raccoon BranchJefferson National Forest4,388
Seng MountainJefferson National Forest6,428
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