Medionidus acutissimus - (I. Lea, 1831)
Alabama Moccasinshell
Taxonomic Status: Accepted
Related ITIS Name(s): Medionidus acutissimus (I. Lea, 1831) (TSN 80262)
Unique Identifier: ELEMENT_GLOBAL.2.120101
Element Code: IMBIV28010
Informal Taxonomy: Animals, Invertebrates - Mollusks - Freshwater Mussels
 
Kingdom Phylum Class Order Family Genus
Animalia Mollusca Bivalvia Unionoida Unionidae Medionidus
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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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: Medionidus acutissimus
Taxonomic Comments: Simpson (1914) and Ortmann (1924) recognized Medionidus parvulus as distinct from Medionidus acutisssimus. Van der Schalie (1938) noted that they integrated. Johnson (1977) synonymized M. parvulus with M. acutissimus. Genetic analysis is needed to determine the proper identification of some populations (e.g., Medionidus specimens from the Conasauga River). The relationship of Medionidus acutissimus to Medionidus parvulus is unclear as the two overlap in shell morphology in parts of their ranges. Further taxonomic questions exist as to the relationship between Mobile Basin M. acutissimus and what appears to be that species in the Choctawhatchee, Yellow, and Escambia drainages as slight conchological differences exist. M. acutissimus from the Escambia, Yellow, and Choctawhatchee River drainages are also similar morphologically to Medionidus penicillatus and some authors have included those populations in the range of M. penicillatus (Johnson, 1977; Butler, 1990; Williams and Butler, 1994), but those populations are included in the range of M. acutissimus by Williams et al. (2008) because faunal distribution patterns suggest that faunas in the Choctawhatchee, Yellow, and Escambia River drainages are more closely related to those of the Mobile Basin than those of the Apalachicola Basin.
Conservation Status
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NatureServe Status

Global Status: G2
Global Status Last Reviewed: 10Dec2013
Global Status Last Changed: 03Jun2005
Rounded Global Status: G2 - Imperiled
Reasons: This is a declining regionally endemic species that could face severe decline or extinction from further loss or degredation of habitat. Although the population in the Sipsey Fork appears to be stable, trends in other populations are towards decline or are not known. It has disappeared from a significant portion of its historical range, including much of southern Alabama and apparently all of the Florida panhandle.
Nation: United States
National Status: N2 (03Jun2005)

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), Florida (SH), Georgia (S1), Mississippi (S1), Tennessee (S1)

Other Statuses

U.S. Endangered Species Act (USESA): LT: Listed threatened (17Mar1993)
U.S. Fish & Wildlife Service Lead Region: R4 - Southeast
IUCN Red List Category: EN - Endangered
American Fisheries Society Status: Threatened (01Jan1993)

NatureServe Global Conservation Status Factors

Range Extent: 250-5000 square km (about 100-2000 square miles)
Range Extent Comments: The type locality for Medionidus acutissimus is the Alabama River, Alabama. Historically, it was known from the Alabama, Tombigbee, Black Warrior, Cahaba, and Coosa Rivers and their tributaries in Alabama, Mississippi, Georgia, and Tennessee (USFWS, 2004). Additional records include the Alabama River, Tombigbee River and tributaries (Luxapalila Creek, Buttahatchie and Sipsey Rivers), Black Warrior River and tributaries (Mulberry Fork, Brushy Creek), Cahaba River, and Coosa River and tributaries (Talladega, Choccolocco Creeks, Chatooga River). The current range of the species includes the Luxapalila Creek, Buttahatchie and Sipsey Rivers in the Tombigbee River drainage; the headwaters of the Sipsey Fork (Brushy Creek) in the Black Warrior River drainage; and the Conasauga River (USFWS, 1993). Mirarchi et al. (2004) lists distribution as throughout the Mobile basin in Alabama, Georgia, Mississippi, and Tennessee (see Parmalee and Bogan, 1998) with specimens from the Gulf Coast drainages west of Apalachicola Basin, tentatively identified (potentially these are an undescribed species). It also occurs in the Tombigbee drainage in Mississippi (Jones et al., 2005). McGregor et al. (2000) reported it as absent from the Cahaba River, Alabama. I t is known only from 6 historical sites in the Choctawhatchee River drainage of Alabama and Florida (Blalock-Herod et al., 2005).

Area of Occupancy: 501-12,500 4-km2 grid cells
Area of Occupancy Comments: Linear occupancy is 200-5000 km.

Number of Occurrences: 1 - 20
Number of Occurrences Comments: At least four river drainages (Mobile, Escambia, Yellow, Choctawhatchee), each of which originally may have constituted one principal "occurrence." Historically, it was widespread throughout theMobile basin; now it occurs sporadically in low numbers with the best populations occurring in the Sipsey Fork drainage. It survives in the Tombigbee River tributaries (Blue Mountain Creek, Luxapalila Creek, Yellow Creek, Buttahatchee River, Sipsey Creek, Lubbub Creek, and Sipsey River), Black Warrior River tributaries (Sipsey Fork and tributaries), and Holly Creek in the Coosa River drainage (USFWS, 2004). It is known from 6 historical sites only in the Choctawhatchee River drainage of Alabama and Florida; recent surveys of these and several other sites in the drainage failed to find any specimens (Blalock-Herod et al., 2005). The species has been reported recently from the Conasauga River inside and adjacent to the Cherokee and Chattahoochee National Forests, Polk Co., Tennessee; as well as Holly Creek, adjacent to the Chattahoochee National Forest, Murray Co., Georgia (Parmalee and Bogan, 1998; Johnson et al., 2005). In the Coosa River basin in Georgia, it is known historically from the Coosa, Etowah, Oostanaula, and Conasauga River drainages but has not been collected live recently (Williams and Hughes, 1998). Johnson and Ahlstedt (2005) located specimens in 2005 in the Luxapallila drainage on the Mississippi/Alabama border. It has likely been recently been extirpated from the Escambia and Yellow River drainages in Alabama and Florida (Williams et al., 2000). Overall in Alabama, it is extant in isolated and widely separated localities in the Mobile Basin and has not been collected from other Gulf Coast drainages since the 1960s (Williams et al., 2008).

Population Size: 2500 - 10,000 individuals
Population Size Comments: This species is not abundant anywhere but is locally common in tributaries of the Sipsey Fork, upper Black Warrior River drainage, Alabama. The highest densities observed are from Sipsey Fork and its headwater tributaries in Bankhead National Forest (0 to 2.8/10 square meters) (Warren and Haag, 1994). Johnson (1977) listed it as once common in the headwater streams in Tennessee and Georgia, where it can even be locally abundant, and claims it was historically common in the Cahaba River, Lily Shoals, Bibb Co., Alabama, but Hurd (1974) was only able to find 22 specimens in 4 of 194 localities surveyed.

Number of Occurrences with Good Viability/Integrity: None to few (0-12)
Viability/Integrity Comments: Except for the Sipsey Fork, populations are small and localized (USFWS, 2000; 2004). Some populations (though localized) in Alabama appear healthy, including the Sipsey Fork in Bankhead National Forest and Sipsey River (457 occupied, 698 unoccupied km) (Mirarchi et al., 2004).

Overall Threat Impact: High
Overall Threat Impact Comments: Habitat modification, sedimentation, and water quality degradation represent the major threats to this species; it may also be threatened by overutilization for commercial, recreational, scientific or educational purposes as well as disease and predation (USFWS, 1993; 2000). Disappearance from significant portions of its range are primarily due to changes in river and stream channels resulting from dams, dredging, or mining, and historic or episodic pollution events. The species is not known to survive in impounded waters, and more than 1700 km of large and small river habitat in the Basin (Mobile) have been impounded by dams for navigation, flood control, water supply, and/or hydroelectric production (USFWS, 2004).

From USFWS (2000):
In the Mobile River basin, the greatest threats are dams (for navigation, water supply, electricity, recreation, and flood control), channelization (causing accelerated erosion and altered depth; and loss of habitat diversity, substrate stability, and riparian canopy), dredging (for navigation or gravel mining), mining (for coal, sand, gravel, or gold) in locally concentrated areas, point-source pollution (industrial waste effluent, sewage treatment plants, carpet and fabric mills, paper mills and refineries in mainstem rivers), and non-point-source pollution (construction, agriculture, silviculture, and urbanization).

Short-term Trend: Decline of 30-70%
Short-term Trend Comments: The populations in the tributaries to the Sipsey Fork appear to be stable. Elsewhere, the status is believed to be declining. It is rare in the Consauga River (Doug Shelton, pers. obs. 1997). The species has disappeared from the mainstem of the Alabama, Tombigbee, Black Warrior, Cahaba, and Coosa rivers (USFWS, 2004; Mirarchi et al., 2004). Johnson (1977) lists it as once common in the headwater streams in Tennessee and Georgia, where it can even be locally abundant, and claims it was historically common in the Cahaba River, Lily Shoals, Bibb Co., Alabama, but Hurd (1974) was only able to find 22 specimens in 4 of 194 localities surveyed. It is known only from 6 historical sites in the Choctawhatchee River drainage of Alabama and Florida; recent surveys of these sites and several other sites in the drainage failed to find any specimens (Blalock-Herod et al., 2005).

Long-term Trend: Decline of 50-70%
Long-term Trend Comments: Johnson (1977) claims that the species was common only in the headwater streams in Tennessee and Georgia but was scarce elsewhere; and that it was fomerly abundant in the Cahaba River in Bibb Co., Alabama, but had become very rare there. The species has not been documented in the Choctawhatchee River of Florida since the 1930s.

Intrinsic Vulnerability: Highly to moderately vulnerable.
Intrinsic Vulnerability Comments: Freshwater mussels are inherently vulnerable to threats from siltation, pollution, eutrophication, channelization, impoundment, collection, drought and water withdrawal, competiton from invasive non-native mussels, and changes to larval host fish populations. Isolated imperiled populations in the Mobile River basin are likely vulnerable to random accidents, such as toxic spills, and to naturally catastrophic events, such as droughts and floods, even if land use and human populations were to remain constant within isolated watersheds (USFWS, 2000).

Environmental Specificity: Narrow. Specialist or community with key requirements common.
Environmental Specificity Comments: This species is tiny, inhabiting the interstices of gravel and cobble substrates, and is very sensitive to sedimentation and erosion (USFWS, 2000).

Other NatureServe Conservation Status Information

Inventory Needs: Continue surveys to determine the extent and status of previously documented populations.

Protection Needs: Maintain high water and benthic habitat (substrate) qualities, as well as adequate flow regimes, throughout all occupied river systems. This may be partially accomplished via establishment of buffers and streamside management zones for all agricultural, silvicultural, mining, and developmental activities; protection of floodplain forests and adjoining upland habitat is paramount. Best management practices to follow include employing forestry practices that cause minimal soil erosion; preventing access of livestock to natural surface waters and drains; situating roads at least 0.25 mi. (0.4 km) from heads of all tributaries, even more on steep slopes; using silt fencing and vegetation to control runoff and siltation at all stream crossings, especially during construction and maintenance; using and maintaining sewer systems rather than septic tanks and stream-dumping for management of wastewater; and avoiding use of agricultural pesticides on porous soils near streams. Prevent damming, dredging, and pollution throughout drainages, but especially near recorded sites. Remove existing dams, but with great care to limit downstream sedimentation. Limit withdrawal of surface and subterranean waters as necessary to maintain normal stream flows, especially during drought. Prevent or limit establishment of invasive species (including zebra mussel, Dreissena polymorpha) to the extent possible. Where appropriate, protect populations through acquisitions and easements over streamside lands by working with government agencies and conservation organizations.
The U.S. Fish and Wildlife Service proposed Critical habitat in 9 units across the species' distribution in the Mobile Basin (USFWS, 2004). The Mobile River Basin recovery plan (USFWS, 2000) calls for: (1) use to the fullest extent existing laws, regulations, and policies to protect listed populations and their habitats, and to develop and encourage a stream management strategy that places high priority on conservation; (2) encourage voluntary stewardship through joint initiatives and individual actions as the only practical and economical means of minimizing adverse effects of private land use and activities within watersheds; and (3) continue to promote research efforts on life histories, sensitivities, and requirements of imperiled aquatic species, and develop technological capabilities to maintain and propagate them.

Distribution
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Global Range: (250-5000 square km (about 100-2000 square miles)) The type locality for Medionidus acutissimus is the Alabama River, Alabama. Historically, it was known from the Alabama, Tombigbee, Black Warrior, Cahaba, and Coosa Rivers and their tributaries in Alabama, Mississippi, Georgia, and Tennessee (USFWS, 2004). Additional records include the Alabama River, Tombigbee River and tributaries (Luxapalila Creek, Buttahatchie and Sipsey Rivers), Black Warrior River and tributaries (Mulberry Fork, Brushy Creek), Cahaba River, and Coosa River and tributaries (Talladega, Choccolocco Creeks, Chatooga River). The current range of the species includes the Luxapalila Creek, Buttahatchie and Sipsey Rivers in the Tombigbee River drainage; the headwaters of the Sipsey Fork (Brushy Creek) in the Black Warrior River drainage; and the Conasauga River (USFWS, 1993). Mirarchi et al. (2004) lists distribution as throughout the Mobile basin in Alabama, Georgia, Mississippi, and Tennessee (see Parmalee and Bogan, 1998) with specimens from the Gulf Coast drainages west of Apalachicola Basin, tentatively identified (potentially these are an undescribed species). It also occurs in the Tombigbee drainage in Mississippi (Jones et al., 2005). McGregor et al. (2000) reported it as absent from the Cahaba River, Alabama. I t is known only from 6 historical sites in the Choctawhatchee River drainage of Alabama and Florida (Blalock-Herod et al., 2005).

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, FL, GA, MS, TN

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
AL Cherokee (01019)*, Etowah (01055)*, Greene (01063), Lawrence (01079), Pickens (01107), Winston (01133)
GA Chattooga (13055)*, Gordon (13129)*, Murray (13213), Walker (13295)*, Whitfield (13313)*
MS Lowndes (28087), Monroe (28095)
TN Bradley (47011), Polk (47139)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 Yellow (03140103)*, Blackwater (03140104)*, Upper Choctawhatchee (03140201)*, Pea (03140202)*, Lower Choctawhatchee (03140203), Sepulga (03140303)*, Lower Conecuh (03140304)*, Escambia (03140305)*, Conasauga (03150101)+, Oostanaula (03150103)+*, Etowah (03150104)*, Upper Coosa (03150105)+*, Middle Coosa (03150106)+*, Lower Coosa (03150107)*, Lower Tallapoosa (03150110)*, Cahaba (03150202)*, Middle Alabama (03150203)*, Lower Alabama (03150204)*, Upper Tombigbee (03160101)+, Buttahatchee (03160103)+, Luxapallila (03160105)+, Middle Tombigbee-Lubbub (03160106), Sipsey (03160107)+, Mulberry (03160109), Sipsey Fork (03160110)+, Locust (03160111)*, Lower Black Warrior (03160113)*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A small freshwater mussel or bivalve mollusk which attains an average adult size of 30mm (1.2 in.) in length. The outer shell is yellow to brownish-yellow with broken green rays across the entire surface of the shell.
General Description: This is a small, delicate species with a narrowly elliptical, thin shell with a well-developed acute posterior ridge that terminates in an acute point on the posterior ventral margin. The posterior slope is finely corrugated. The periostracum is yellow to brownish yellow, with broken green rays across the entire surface of the shell. The thin nacre is translucent along the margins and salmon-colored in the umbos (FWS, 2003).
Diagnostic Characteristics: Medionidus acutissimus is distinguished from the similar species Medionidus parvulusby its acute posterior ridge, sharply pointed apex, salmon colored nacre, and smaller size (U. S. Fish and Wildlife Service, 1993).
Reproduction Comments: Freshwater mussel larvae (glochidia) are brooded in the gills of the female and when mature are released into the water where they spend a brief period as obligate parasites on the gills, fins, or other external parts of fish until they drop off to the benthos. In the laboratory, Haag and Warren (1997) identified the following fish hosts: Fundulus olivaceus, Etheostoma artesiae (redspot darter), Etheostoma douglasi, Etheostoma nigrum (johnny darter), Etheostoma rupestre (rock darter), Etheostoma stigmaeum (speckled darter), Etheostoma swaini (Gulf darter), Medionidus acutissimus (blackbanded darter), Etheostoma whipplei, Percina nigrofasciata, Ammocryptaq beani (naked sand darter), Ammocrypta meridiana (southern sand darter), Percina vigil (saddleback darter), and Percina caprodes. Females were found gravid with mature glochidia from late February to mid March in water temperatures of 8-13 degrees C (Haag and Warren, 1997; 2001). This species is a long-term brooder and females are gravid from October to June and live embedded in the stream bottom until March when they anchor themselves to gravel by a byssal thread, and lie exposed, displaying a black mantle lure apparently to attract potential host fish; which include Ammocrypta beani (naked sand darter), Ammocrypta meridiana (southern sand darter), Etheostoma nigrum (Johnny darter), Etheostoma rupestre (rock darter), Etheostoma stigmaeum (speckled darter), Etheostoma swaini (Gulf darter), Etheostoma artesiae (redspot darter), Percina nigrofasciata (blackbanded darter), and Percina vigil (saddleback darter) (USFWS, 2003; Haag and Warren, 2003).
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: N
Riverine Habitat(s): BIG RIVER, CREEK, High gradient, Low gradient, MEDIUM RIVER, Moderate gradient, Riffle
Special Habitat Factors: Benthic
Habitat Comments: This species is usually found in sand on the margins of streams with a typical sand and gravel substrate in clear water of moderate flow in small to large rivers (Doug Shelton, pers. obs., 1995; USFWS, 2000).
Length: 3 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: This species was listed as threatened in 1993 and a recovery plan created (USFWS, 2000) and critical habitat has been designated in Mississippi in the East Fork Tombigbee River, Bull Mountain Creek, Buttahatchee River, Luxapalila Creek; in Alabama in the Buttahatchee River, Luxapalila Creek, Coalfire Creek, Lubbub Creek, Sipsey River, Trussels Creek, Sucarnoochee River, Sipsey Fork, Cahaba River, Bogue Chitto Creek, Lower Coosa River; and in Georgia in the Oostanuala complex (457 occuppied, 698 unoccuppied km) (USFWS, 2004).

A specific recovery plan has been created for the Mobile River basin (USFWS, 2000) which contains the following objectives: (1) protect habitat integrity and quality of river and stream segments that currently support or could support imperiled aquatic species, (2) consider options for free-flowing river and stream mitigation strategies that give high priority to avoidance and restoration, (3) promote voluntary stewardship as a practical and economical means of reducing nonpoint pollution from private land use, (4) encourage and support community based watershed stewardship planning and action, (5) develop and implement programs and materials to educate the public on the need and benefits of ecosystem management, and to involve them in watershed stewardship, (6) conduct basic research on endemic aquatic species and apply the results toward management and protection of aquatic communities, (7) develop and implement technology for maintaining and propagating endemic species in captivity, (8) reintroduce aquatic species into restored habitats, as appropriate, (9) monitor listed species population levels and distribution and periodically review ecosystem management strategy, (10) coordinate ecosystem management actions (more detail in USFWS, 2000).

Biological Research Needs: 1. Conduct life history studies with an emphasis on fish host identification. 2. Conduct genetic analyses to determine the proper identification of certain populations; e.g., the identification of Medionidus specimens from the Conasauga River can be problematic. In addition to Medionidus acutissimus and M. parvulus, M. conradicus may also exist in the Conasauga River (D. Stansbery - per. comm., 9/27/97). 3. Determine if culturing the species is a viable tool for conservation. 4. Assess sites for potential reintroduction if culturing should prove successful.
Population/Occurrence Delineation
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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 (jay_cordeiro@natureserve.org) for a complete list of freshwater mussel taxa sorted by flow regime.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 08Jan2014
NatureServe Conservation Status Factors Author: Jackson, D. R. (2013); Cordeiro, J. (2009)
Element Ecology & Life History Edition Date: 12Feb2007
Element Ecology & Life History Author(s): Cordeiro, J.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Blalock-Herod, H. N., J. J. Herod, J. D. Williams, B. N. Wilson, and S. W. McGregor. 2005. A historical and current perspective of the freshwater mussel fauna (Bivalvia: Unionidae) from the Choctawhatchee River drainage in Alabama and Florida. Bulletin of the Alabama Museum of Natural History 24:1-26.

  • HURD, J.C. 1974. SYSTEMATICS & ZOOGEOGRAPHY OF THE UNIONACEAN MOLLUSKS OF THE COOSA RIVER DRAINAGE OF ALABAMA, GEORGIA, & TENNESSEE. PH.D. DISSERTATION, AUBURN UNIV., AL. 240 PP.

  • Haag, W. R., and M. L. Warren, Jr. 1997. Host fishes and reproductive biology of 6 freshwater mussel species from the Mobile Basin, USA. Journal of the North American Benthological Society, 16(3): 576-585.

  • Haag, W.R. and M.L. Warren, Jr. 2003. Host fishes and infection strategies of freshwater mussels in large Mobile Basin streams, USA. Journal of the North American Benthological Society 22(1):78-91.

  • Howard, A.D. 1915. Some exceptional cases of breeding among the Unionidae. The Nautilus 29:4-11.

  • Hurd, J.C. 1974. Systematics and zoogeography of the Unionacean mollusks of the Coosa River drainage of Alabama, Georgia, and Tennessee. University Microfilms International, Ann Arbor, Michigan. Auburn University. Ph.D. dissertation. 240 pp., 10 tables, 6 fig., + 63 maps.

  • Johnson, P.D. and S.A. Ahlstedt. 2005. Results of a brief survey for freshwater mussels in the Yellow Creek Watershed, Lowndes County, Mississippi and Lamar and Fayette Counties, Alabama. Report to the U.S. Fish and Wildlife Service, Daphne, Alabama. Unpainated.

  • Johnson, P.D., C. St. Aubin, and S.A. Ahlstedt. 2005. Freshwater mussel survey results for the Cherokee and Chattahoochee districts of the United States Forest Service in Tennessee and Georgia. Report to the U.S. Fish and Wildlife Service, Daphne, Alabama. 32 pp.

  • Johnson, R.I. 1977. Monograph of the genus Medionidus (Bivalvia: Unionidae) mostly from the Apalachicolan region, southeastern United States. Occasional Papers on Mollusks, 4(56): 161-187.

  • Lefevre, G. and W.T. Curtis. 1912. Studies on the reproduction and artificial propogation of fresh-water mussels. Bulletin of the Bureau of Fisheries 30:102-201.

  • McGregor, S.W., P.E. O'Neil, and J.M. Pierson. 2000. Status of the freshwater mussel (Bivalvia: Unionidae) fauna of the Cahaba River system, Alabama. Walkerana, 11(26): 215-237.

  • Mirarchi, R.E., J.T. Garner, M.F. Mettee, and P.E. O'Neil. 2004b. Alabama wildlife. Volume 2. Imperiled aquatic mollusks and fishes. University of Alabama Press, Tuscaloosa, Alabama. xii + 255 pp.

  • Moyle, P. and J. Bacon. 1969. Distribution and abundance of molluscs in a fresh water environment. Journal of the Minnesota Academy of Science 35(2/3):82-85.

  • Ortmann, A.E. 1924. The naiad fauna of Duck River in Tennessee. The American Midland Naturalist, 9: 18-62.

  • Parmalee, P.W. and A.E. Bogan. 1998. The Freshwater Mussels of Tennessee. University of Tennessee Press: Knoxville, Tennessee. 328 pp.

  • Parmalee, P.W. and A.E. Bogan. 1998. The freshwater mussels of Tennessee. University of Tennessee Press, Knoxville, Tennesee. 328 pp.

  • Simpson, C.T. 1914. A Descriptive Catalogue of the Naiades or Pearly Fresh-water Mussels. Bryant Walker: Detroit, Michigan. 1540 pp.

  • Strayer, D. 1983. The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A. Freshwater Biology 13:253-264.

  • Strayer, D.L. 1999a. Use of flow refuges by unionid mussels in rivers. Journal of the North American Benthological Society 18(4):468-476.

  • Strayer, D.L. and J. Ralley. 1993. Microhabitat use by an assemblage of stream-dwelling unionaceans (Bivalvia) including two rare species of Alasmidonta. Journal of the North American Benthological Society 12(3):247-258.

  • 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.

  • U.S. Fish and Wildlife Service (USFWS). 1993. Endangered status for eight freshwater mussels and threatened status for three freshwater mussels in the Mobil River drainage. Final rule. Federal Register, 58(60): 14330-14340.

  • U.S. Fish and Wildlife Service (USFWS). 1997. Draft Recovery Plan for the Mobile River basin aquatic ecosystem. U.S. Fish and Wildlife Service, Southeast Region, Atlanta, Georgia.

  • U.S. Fish and Wildlife Service (USFWS). 2000. Recovery plan for the Mobile River basin aquatic ecosystem. U.S. Fish and Wildlife Service, Southeast Region, Atlanta, Georgia. 128 pp.

  • U.S. Fish and Wildlife Service (USFWS). 2003. Endangered and Threatened Widlife and plants; proposed designation of critical habitat for three threatened mussels and eight endangered mussels in the Mobile River basin; proposed rule. Federal Register, 68(58): 14752-14832.

  • USFWS. 1991. ENDANGERED & THREATENED WILDLIFE & PLANTS; PROPOSED ENDANGERED STATUS FOR EIGHT FRESHWATER MUSSELS AND PROPOSED THREATENED STATUS THREE FRESHWATER MUSSELS IN THE MOBILE RIVER DRAINAGE. FEDERAL REGISTER, VOL 56, NO. 223.

  • USFWS. 1993. ENDANGERED AND THREATENED WILDLIFE AND PLANTS; ENDANGERED STATUS FOR EIGHT FRESHWATER MUSSELS AND THREATENED STATUS FOR THREE FRESHWATER MUSSELS IN THE MOBILE RIVER DRAINAGE. FEDERAL REGISTER, VOL. 58, NO. 50.

  • Van der Schalie, H. 1938a. The naiad fauna of the Huron River in southeastern Michigan. Miscellaneous Publication of the Museum of Zoology, University of Michigan 40:7-78.

  • Watters, G.T. 1992a. Unionids, fishes, and the species-area curve. Journal of Biogeography 19:481-490.

  • Williams, J. D.  2013.  Comments on the status of the mussel Medionidus actutissimus and its occurrence in Florida.  E-mail to D. Jackson, dated 15 December 2013.

  • Williams, J. D.  2013b.  Comments on the status of the mussel Medionidus actutissimus and its occurrence in Florida.  E-mail to D. Jackson, dated 15 December 2013.

  • Williams, J. D., A. E. Bogan, and J. T Garner. 2008. Freshwater mussels of Alabama & the Mobile Basin in Georgia, Mississippi, & Tennessee. University of Alabama Press, Tuscaloosa, Alabama. 908 pages.

  • Williams, J. D., A. E. Bogan, and J. T. Garner. 2008. Freshwater Mussels of Alabama and the Mobile Basin in Georgia, Mississippi and Tennessee. University of Alabama Press, Tuscaloosa, Alabama. 908 pp.

  • Williams, J. D., R. S. Butler, G. L. Warren, and N. A. Johnson.  2014.  Freshwater Mussels of Florida.  University of Alabama Press, Tuscaloosa.  498 pp.

  • Williams, J. D., R. S. Butler, G. L. Warren, and N. A. Johnson.  2014a.  Freshwater Mussels of Florida.  University of Alabama Press, Tuscaloosa, Alabama. 498 pp.

  • Williams, J.D. and M.H. Hughes. 1998. Freshwater mussels of selected reaches of the main channel rivers in the Coosa drainage of Georgia. U.S. Geological report to U.S. Army Corps of Engineers, Mobile District, Alabama. 21 pp.

  • Williams, J.D., M.L. Warren, Jr., K.S. Cummings, J.L. Harris, and R.J. Neves. 1993b. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.

References for Watershed Distribution Map
  • Biological Resources Division, USGS. 1997. Database of museum records of aquatic species. Compiled by J. Williams (USGS-BRD, Gainesville, FL).

  • Blalock-Herod, H.N., J.J. Herod, J.D. Williams, B.N. Wilson, and S.W. McGregor. 2005. A historical and current perspective of the freshwater mussel fauna (Bivalvia: Unionidae) from the Choctawhatchee River drainage in Alabama and Florida. Bulletin of the Alabama Museum of Natural History, 24: 1-26.

  • Jones, R.L., W.T. Slack, and P.D. Hartfield. 2005. The freshwater mussels (Mollusca: Bivalvia: Unionidae) of Mississippi. Southeastern Naturalist, 4(1): 77-92.

  • U.S. Fish and Wildlife Service (USFWS). 2004. Endangered and Threatened Widlife and plants; designation of critical habitat for three threatened mussels and eight endangered mussels in the Mobile River basin; final rule. Federal Register, 69(126): 40083-40171.

  • Williams, J.D., A.E. Bogan, and J.T. Garner. 2008. Freshwater Mussels of Alabama & the Mobile Basin in Georgia, Mississippi & Tennessee. University of Alabama Press: Tuscaloosa, Alabama. 908 pp.

  • Williams, J.D., H.N. Blalock, A. Benson, and D.N. Shelton. 2000. Distribution of the freshwater mussel fauna (Bivalvia: Margaritiferidae and Unionidae) in the Escambia and Yellow river drainages in southern Alabama and western Florida. Final Report for the U.S. Fish and Wildlife Service, Jacksonville, Florida. 61 pp.

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