Cracking Pearlymussel

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Cracking Pearlymussel

Hemistena lata

ListedSeptember 28, 1989
FamilyUnionidae (Freshwater Mussel)
DescriptionGreenish brown to brown elongated shell, with dark green rays and a pale blue to purple interior.
HabitatRiffles on medium-sized streams.
ReproductionFemale stores sperm in gills; glochidia are released into the stream after hatching.
ThreatsDam construction, water pollution.
RangeKentucky, Tennessee, Virginia


The cracking pearlymussel is medium-sized, with a thin, elongated shell. The outer surface is greenish brown to brown, usually with broken, dark green rays. The interior is pale blue to purple. The species has also been known as Lastena lata.


See the Upland Combshell (Epioblasma metastriata ) entry.


The cracking pearlymussel inhabits mediumsized streams where it buries itself in gravel riffles. Freshwater mussels feed by filtering food particles from the water Their reproductive life cycle involves a stage when the mussel larvae attach to the gills of host fish species.


The cracking pearlymussel was once widely distributed in the Ohio, Cumberland, and Tennessee River systems. In the Ohio River Basin it was found from Ohio downstream to Illinois. In Indiana and Illinois it was known from the White, Wabash, and Tippecanoe Rivers. In Kentucky the species inhabited the upper Cumberland, Big South Fork, Green, and Kentucky Rivers. In Tennessee, it was known from the Tennessee, Cumberland, Powell, Clinch, Holston, Elk, Duck, and Buffalo Rivers. It was found in Virginia in the Powell, Clinch, and Holston Rivers and in Alabama in the Tennessee River.

Only three populations of the cracking pearly-mussel are known to survive: in the Clinch River, Hancock County, Tennessee, and Scott County, Virginia; in the Powell River, Hancock County, Tennessee, and Lee County, Virginia; and in the Elk River, Lincoln County, Tennessee. It is possible that small populations persist in the Green River, Hart and Edmonson counties, Kentucky, as well as in the Tennessee River below Pickwick Dam.

In 1979, the Tennessee Valley Authority (TVA) sampled 78 sites over almost 100 miles of the Powell River and found the cracking pearly mussel at only three sites. A 1980 survey of 108 sites over 172 miles of the Elk River found the species at only two sites.

The largest population of this mussel is in the Clinch River. A TVA survey of 141 sites over 174 miles in 1978 and 1983 found the species at 16 sites.

No live cracking pearlymussels have been taken from the Green or Tennessee Rivers in recent years, but there remains suitable habitat in each river and shells have been found, leading researchers to believe that small populations persist.


The cracking pearly mussel has declined over its historic range because of the alteration and pollution of its streambed habitat. The extensive series of dams constructed in the area by TVA has altered much of the original aquatic environment inhabited by freshwater mussels. The dam reservoirs convert stream environments into lakes, producing a corresponding change in the aquatic life. In addition, the water quality of the Powell River and, to a lesser extent, the Clinch River has been degraded by pollution associated with coal mining. In the past, the Clinch River has suffered large fish and mussel kills from toxic discharges from a power plant. Oil and gas production, cold water discharges from reservoirs, channel maintenance, and gravel dredging are other activities that have contributed to the decline of freshwater mussels.

Conservation and Recovery

The Fish and Wildlife Service published a Recovery Plan for the cracking pearlymussel in 1991.The species is only known to survive at three sites, the largest of which is in the Clinch River. Conservation of this endangered mollusk requires that its critical habitat is strictly protected from potential impoundment, other disturbances (such as channel dregding), and pollution associated with coal mining, the operation of dams, and land-use practices causing siltation and inputs of nutrients and other chemicals. The known populations of the cracking pearlymussel must be monitored, additional populations searched for, and research undertaken into its basic biology and ecological requirements for breeding.


Asheville Field Office
U.S. Fish and Wildlife Service
160 Zillicoa Street
Asheville, North Carolina 28801


Ahlstedt, S. A. 1986. "Cumberland Mollusk Conservation Program Activity 1: Mussel Distribution Surveys." Tennessee Valley Authority, Norris, Tennessee.

Ahlstedt, S. A., and J. J. Jenkinson. 1987. "A Mussel Die-off in the Powell River, Virginia and Tennessee, in 1983." In Proceedings of the Workshop on Die-offs of Freshwater Mussels in the United States, June 23-25, 1986, edited by Richard Neves. Davenport, Iowa.

Bates, J. M., and S. D. Dennis. 1985. "Mussel Resource SurveyState of Tennessee." Tennessee Wildlife Resources Agency Technical Report No. 85-3.

U.S. Fish and Wildlife Service. 1991. "Cracking Pearlymussel (Hemistena [= Lastena ] lata ) Recovery Plan." Atlanta, Georgia.