Rough Pigtoe Pearly Mussel
Pleurobema plenum
Summary 3
The rough pigtoe pearly mussel or rough pigtoe, scientific name Pleurobema plenum, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.
Distribution 4
Global Range: (250-1000 square km (about 100-400 square miles)) Historically, this species was widely distributed in the Ohio, Cumberland, and Tennessee river drainages (USFWS, 1984). Currently, it is present in an undetermined number of miles below three Tennessee River mainstem dams (Pickwick, Wilson, and Guntersville) and the upper Clinch River between river miles 323 and 154 (likely only extant and viable between rm 189 and 154) primarily on the Tennessee side at the Virginia border. Although reported by Parmalee et al. (1980) from the middle Cumberland River between 1977 and 1979, it was not found in recent surveys by Tennessee Valley Authority (1976) or Sickel and Chandler (1996). It is present on the Green River, Kentucky between locks 4 and 5 and in the Barren River (Green River tributary in Kentucky) below Lock and Dam 1 (USFWS, 1984). Clarke (1983) found a single living specimen in the Green River near Glenmore, Kentucky. Historical populations are gone in the upper Ohio River drainage and western parts of its range (Arkansas, Missouri, and Kansas) if in fact it ever occurred there. In Alabama, In Alabama, extant populations are in the Tennessee River tailwaters of Wilson Dam (very rare) and possibly Guntersville Dam (Mirarchi et al., 2004) but historically it is known from the following counties: Colbert, Lauderdale, Madison, Morgan, Marshall, Lawrence, Limestone.
Habitat 5
Habitat Type: Freshwater
Comments: This species is found in medium to large rivers (20 m wide or greater) in sand, gravel, and cobble substrates in shoals. It is occasionally found on flats and muddy sand (Gordon and Layzer, 1989; USFWS, 1984).
Iucn red list assessment 6
Red List Category
Red List Criteria
Version
Year Assessed
- Needs updating
Assessor/s
Reviewer/s
Contributor/s
History
-
1994Endangered (E)
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1990Endangered (E)
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1988Endangered (E)
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1986Endangered (E)
Nature serve conservation status 7
Rounded Global Status Rank: G1 - Critically Imperiled
Reasons: Distribution is greatly fragmented and the remaining occurrences are few and highly disjunct. Long-term viability of most populations is questionable, especially those in large rivers where zebra mussel populations are now established. Questionable taxonomic status and problems in identification complicate the problem.
Intrinsic Vulnerability: Highly vulnerable
Comments: Sensitive to pollution, siltation, habitat perturbation, inundation, commercial harvest, and loss of glochidial hosts. The species currently has a disjunct distribution from what was once a widespread distribution limiting dispersal and exchange of genetic material.
Environmental Specificity: Narrow. Specialist or community with key requirements common.
Comments: This species is found in medium to large rivers (20 m wide or greater) in sand, gravel, and cobble substrates in shoals. It is occasionally found on flats and muddy sand (Gordon and Layzer, 1989; USFWS, 1984).
Other Considerations: It is considered as endangered by the freshwater mussel subcommittee of the endangered species committee of the American Fisheries Society (Williams et al., 1993).
Threats 8
Degree of Threat: Very high - high
Comments: Smith (1971) ranked the causes of extirpation or declines in fish species as follows: siltation, drainage of bottomland lakes, swamps, and prairie marshes, desiccation during drought, species introductions, pollution, impoundments, and increased water temperatures. All of these factors render habitats unsuitable, cause extirpations, and lead to the isolation of populations thereby increasing their vulnerability to extirpation for many aquatic species (including mussels) throughout North America. Zebra mussels, Dreissena polymorpha, have destroyed mussel populations in the Great Lakes and significantly reduced mussels in many of the large rivers of eastern North America. Zebra mussels have the potential to severely threaten other populations especially if they make their way into smaller streams. Pollution through point (industrial and residential discharge) and non-point (siltation, herbicide and fertilizer run-off) sources is perhaps the greatest on-going threat to this species and most freshwater mussels. Lowered dissolved oxygen content and elevated ammonia levels (frequently associated with agricultural runoff and sewage discharge) have been shown to be lethal to some species of freshwater naiads (Horne and McIntosh, 1979). Residential, mineral and industrial development also pose a significant threat. Rotenone, a toxin used to kill fish in bodies of water for increased sport fishery quality, has been shown to be lethal to mussels as well (Heard, 1970). Destruction of habitat through stream channelization and maintenance and the construction of dams is still a threat in some areas. Impoundments reduce currents that are necessary for basic physiological activities such as feeding, waste removal and reproduction. In addition, reduced water flow typically results in a reduction in water oxygen levels and a settling out of suspended solids (silt, etc.), both of which are detrimental. Dredging of streams has an immediate effect on existing populations by physically removing and destroying individuals. Dredging also affects the long-term recolonization abilities by destroying much of the potential habitat, making the substrates and flow rates uniform throughout the system. Natural predators include raccoons, otter, mink, muskrats, turtles and some birds (Simpson, 1899; Boepple and Coker, 1912; Evermann and Clark, 1918; Coker et al., 1921; Parmalee, 1967; Snyder and Snyder, 1969). Domestic animals such as hogs can root mussel beds to pieces (Meek and Clark, 1912). Fishes, particularly catfish, Ictalurus spp. and Amieurus spp., and freshwater drum, Aplodinotus grunniens, also consume large numbers of unionids.
The federal recovery plan (USFWS, 1984) lists the following threats: impoundment (for flood control, navigation, hydroelectric power, and recreation), siltation (due to strip mining, coal washing, dredging, farming, logging, and road construction), pollution (from municipal, agricultural, and industrial discharges). Invasion by zebra mussels is a recent threat to this species' survival.
Trends 9
Global Short Term Trend: Decline of 70 to >90%
Comments: Once widely distributed in the Ohio, Tennessee, and Green Rivers and some of the largest tributaries, this species is now severely declining (Clarke, 1983; USFWS, 1984). In Illinois, it was formerly widely distributed in the Wabash and Ohio Rivers but is not extirpated from the state (Cummings and Mayer, 1997).
Global Long Term Trend: Decline of 70-90%
Comments: The species has declined significantly to only the Tennessee, Cumberland, Clinch, Green, and Barren Rivers (USFWS, 1984). It is extirpated in Pennsylvania (Bogan, 1993; Spoo, 2008) where it formerly occurred in the Upper Ohio and Middle Allegheny-Redbank drainages (Ortmann, 1919). It is also extirpated from Ohio, where it occurred in the Ohio River basin from Buffington Island to Cincinnati (Watters, 1995) and th elower Muskingum and Scioto Rivers (subfossil) below Columbus (Watters et al., 2009) including Hannibal dam pool (Little Muskingum section) where it was last seen in 2001 (Watters and Flaute, 2010). It is also extirpated in Virginia where it once occurred in the Clinch River although it may still survive as a relictual population in the Tennessee portion (Ahlsteadt, 1991; Parmalee and Bogan, 1998). Alabama distribution has been reduced to the entire northern portion of the state including lower reaches of the Elk and Paint Rock Rivers to possibly two relict populations at Wilson and Guntersville Dams (Mirarchi et al., 2004; Williams et al., 2008). It is extirpated from the McAlpine dam pool in the Ohio River at Louisville, Kentucky (and Indiana) (Watters and Flaute, 2010).
Sources and Credits
- (c) Tim Lane, some rights reserved (CC BY-NC-ND), https://www.flickr.com/photos/119210184@N05/12940697553/
- USFWS, no known copyright restrictions (public domain), http://commons.wikimedia.org/wiki/File:Pleurobema_plenum.jpg
- Adapted by rkkessler from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Pleurobema_plenum
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28870220
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28870228
- (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34659741
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28870213
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28870218
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28870217
