Littlewing Pearlymussel
Scientific Name: Pegias fabula
Classification: Federal and State Endangered
Photo Credit: NCWRC
This species was described by Isaac Lea in 1838 from the Stones River in Tennessee. The little-wing pearlymussel is one of the smallest freshwater mussel species: adults rarely exceed 35 mm in length. The species' name is descriptive of its wing-like appearance.
The periostracum is usually eroded, giving the shell a chalky or ashy white appearance. When the periostracum is present, the shell is light green or dark yellowish brown with dark rays of variable width along the shell's anterior surface. The nacre is whitish on the anterior border and salmon or flesh colored in the beak cavity. Lateral teeth are short, vestigial, or entirely absent. The left valve has an irregular triangular pseudocardinal tooth, sometimes with the vestige of another tooth in front of it, and the right valve has a single triangular pseudocardinal tooth. This species is sexually dimorphic.
Distribution
The little-wing pearlymussel is a Cumberlandian species endemic to the southern Appalachian Mountains and the Cumberland Plateau Region. Historically, the little-wing pearly mussel probably inhabited many of the small to medium tributaries of the Tennessee and Cumberland River systems in Alabama, Tennessee, Kentucky, Virginia and North Carolina. Historical records exist for 24 stream reaches in these states, but the species is presently known from only six stream reaches. The rarity of collections of the species throughout historic and recent times may be due to its small size and often eroded condition or to its preference for tributary streams. An additional factor may be the short time (spawning periods) during which specimens are near the substrate surface where they are visible. NOTE: All headwater areas that flow into these occupied habitats should receive special management.
Habitat Preferences
This species inhabits cool, clear, high-gradient streams. The little-wing pearlymussel is a lotic, riffle dwelling species that is usually found in the headwaters of high-gradient tributary streams. Individuals have been found in the transition zone between pools and riffles, buried under large flat rocks, and in gravel substrata adjacent to water willow beds. During spawning, it is often found lying on top of the bottom substrate.
Life History
Gravid females of this species have been reported in September and October suggesting that the little-wing pearlymussel is bradytictic breeder, holding glochidia from mid-summer through the following spring. Fish reported as hosts for this species include greenside and emerald redline darters. Based on field observations, banded sculpin and redline darter also may serve as host species because they have been observed under large flat rocks and on gravel shoals where little-wing pearlymussels are known to occur.
General Life History for Mussels
Shell Anatomy
