FWS Focus



The pale lilliput is a small freshwater mussel that historically occurred in river systems in northern Alabama and central Tennessee.  Currently, populations of the pale lilliput are limited to the headwaters of the Paint Rock River system in northern Alabama and to Lick Creek, a tributary to the Duck River, in central Tennessee.

Scientific Name

Toxolasma cylindrellus
Common Name
pale lilliput
pale lilliput pearly mussel
Pale lilliput (pearlymussel)
FWS Category

Location in Taxonomic Tree

Identification Numbers



Characteristic category

Physical Characteristics

Size & Shape
  • This small freshwater mussel usually measures less than 1.7 inches (44 millimeters). 
  • It is elongate and elliptical, becoming somewhat cylindrical in shape (Parmalee and Bogan 1998), with the female having an outline more oval in shape than that of the male. 
  • The shell is moderately thin and somewhat compressed (Williams et al. 2008).
Color & Pattern
  • The shell is rayless with a tawny to yellowish green hue (Williams et al. 2008).
  • The nacre (inner shell layer) is often purple to coppery in color (Parmalee and Bogan 1998; Williams et al. 2008).
Characteristic category

Life Cycle

  • The species is a short-term brooder and is gravid from late summer or autumn into the following summer (Williams et al. 2008).
  • Suitable host fish include the Northern Studfish (Fundulus caetenotus), Southern Studfish (Fundulus stellifer) (although this species does not co-occur with the pale lilliput), Blackspotted Topminnow (Fundulus olivaceus), and Blackstripe Topminnow (Fundulus notatus) (Johnson 2018).
  • Females of the pale lilliput have been observed to migrate to the margins of streams when gravid which is thought to increase the likelihood of encountering a host fish.
Characteristic category



The pale lilliput historically occurred in a wide variety of habitats from small creeks to large rivers.  However, it currently seems to persist only in headwater-sized streams usually in less than three feet of water, with sand and gravel substrates and where flows are slow to moderate (Parmalee and Bogan 1998; Williams et al. 2008). 

River or Stream

A natural body of running water.


  • Historic Range - The pale lilliput historically occurred from the middle reaches of the Tennessee River system across northern Alabama and in the Duck River system in central Tennessee (Ortman 1924, Ortman 1925; Parmalee and Bogan 1998; Mirarchi 2004; Williams et al.).
  • Current Range
    • Natural populations – It was previously considered extirpated from the Duck River (Ahlstedt et al. 2017); however, a population is now known to occur in Lick Creek, a tributary to the Duck River in Maury County, Tennessee.  The only other known natural population for the pale lilliput is believed to be limited to the upper reaches of the Paint Rock River system in Jackson County, Alabama, and potentially in its headwaters in Franklin County, Tennessee (Parmalee and Bogan 1998).
    • Renintroductions – Since 2014, the Duck River has received over 3,500 lab-reared individuals, while the Paint Rock River has received approximately 3,600 (Johnson 2020).  Additional stocking sites in the Elk River, Giles County, Tennessee; Bear Creek, Colbert County, Alabama; Big Rock Creek, Marshall County, Tennessee; and Lick Creek, Williamson County, TN, have received over 1,500 individuals (Hubbs 2019; Johnson 2020).  Evidence of recruitment was documented in 2018 by the discovery of juvenile individuals in the vicinity of the stocking sites in the Duck River, Lick Creek, and Paint Rock River (P. Johnson pers. comm. 2018).  Further monitoring will be required to determine if the reintroduced populations have been successfully established and viable.

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