Pale Lilliput

Pale Lilliput, Toxolasma cylindrellus, copyright photo by the Alabama Aquatic Biodiversity Center

Common Name: Pale Lilliput
Scientific Name: Toxolasma cylindrellus
Other Names: None.

Size: 1-3/8 inches

Description: Has moderately solid shell (max. length = 35 mm [1 3/8 in.]), elongate and elliptical in outline, and inflated in some older specimens. Anterior margin rounded and posterior margin obliquely angled dorsally, rounded ventrally.  Dorsal and ventral margins usually straight.  Females differ slightly from males in having a weak marsupial swelling posteriorly.  Posterior ridge low or absent.  Shell disk and posterior slope without sculpture.  Umbos moderately inflated, but elevated only slightly above hinge line.  Periostracum has cloth-like texture and is tawny or yellowish green, without rays. Pseudocardinal teeth short and stumpy; lateral teeth short and straight.  Interdentum narrow and umbo cavity shallow.  Shell nacre white outside of pallial line and coppery purple inside it.  (Modified from Simpson 1914, Parmalee Bogan 1998)

Distribution: Endemic to Tennessee River drainage, where historically found in some tributaries from Sequatchie River system downstream to Duck River system (Parmalee and Bogan 1998).  One possible record from a Mobile Basin stream in northwestern Georgia (Parmalee and Bogan 1998).  Apparently, has been eliminated throughout distribution, except in Paint Rock River system, where rare (Ahlstedt 1995).

Habitat: Large creek and small rivers, typically found in gravel in moderate current (Parmalee and Bogan 1998).

Life History and Ecology: A long-term brooder.  Glochidial hosts unknown.

Basis for Status Classification: Vulnerable to extinction due to extremely limited distribution, rarity, and susceptibility to habitat degradation. Classified as endangered throughout its distribution (Williams et al. 1993) and in Alabama (Stansbery 1976a, Lydeard et al. 1999).  Listed as endangered by the U.S. Fish and Wildlife Service in 1976.

above from Alabama Wildlife, Volume 2 (2004), prepared by Jeffrey T. Garner

Prioritization: Tier 1
Global status: G1
Conservation status: 
   Federal: Endangered
   State: AL - P1; TN - Endangered

Population status: Endemic to the Cumberlandian Region, this species was historically restricted to the middle Tennessee system. It currently exists only in Estill Fork of the Paint Rock drainage and is currently stable. Its current restriction to a single river reach makes it highly susceptible to extinction. USFWS indicated five populations are needed for recovery.

Potential reintroduction streams: Tennessee River system – lower Paint Rock, Jackson / Marshall County, AL (H); Limestone Creek, Limestone County, AL (H); Duck River, Maury County, TN (H); Big Rock Creek, Marshall County, TN (M).

Reproductive biology: Bradytictic. Current host fish work inconclusive. Juvenile mussels will transform in low very numbers on a broad range of fish hosts. Recent AABC trials have had the best success with Studfish, often a host generalist.

Propagation difficulty: High.

Recommended priority actions: 1) Reintroduce into the lower Paint Rock River, Limestone Creek, or Duck River.

Reintroduction potential: Low.

from "Plan for the population restoration and conservation of freshwater mollusks of the Cumberlandian Region" 2010, prepared by the Cumberlandian Region Mollusk Restoration Committee.

Note: In Alabama, it is illegal to release or stock or move any fish, mussel, snail or crayfish to any public waters without a permit.