Cracking Pearlymussel

Cracking Pearlymussel
Hemistena lata
Conservation status
Critically Endangered (IUCN 2.3) [1]
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Unionoida
Family:	Unionidae
Genus:	Hemistena
Species:	H. lata
Binomial name
Hemistena lata Rafinesque, 1820

The Cracking Pearlymussel (Hemistena lata) is an endangered species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae.

This species is native to the United States, where it remains only in Tennessee and Virginia. It was originally distributed in the Ohio River, Cumberland River and Tennessee River systems, but it has been extirpated from most of its previous range.

Parmalee and Bogan reported that there were still populations in the Clinch River in Tennessee.^[2] Other populations that are known to survive are located in the Powell and Elk Rivers.^[3]

Shell description

These mussels have thin, fairly weak, elongated shells. The shells may reach up to 69 millimetres (2.7 in) in height The outer coloring of the shell varies from yellow to brown, while the interior of the shell is pale bluish white, with a purple beak cavity.^[2]

Ecology

This species spends its adult life buried under the sand or mud in the bottom of medium-sized, flowing rivers. The females capture sperm released into the water by males. They store the sperm until they need them to fertilize their eggs. After fertilization, the females release the larvae into the river where the larvae attach to fish. Once the larva mature into juveniles with shells, they leave their host fish and drop to the sediment where they bury themselves.^[4] This process, therefore, requires an environment with ample fish to act as hosts. They prefer relatively shallow (usually less than 2 ft deep) water with a moderate current.^[2]

Conservation

The main threats to the continued existence of this species are habitat changes due to damming of rivers, silting of rivers due to erosion caused by construction, farming and logging, and poisioning due to agricultural and industrial pollution.^[4] The U.S. Fish and Wildlife Service has created a recovery plan for this species.^[5]

References

1. ^ A. E. Bogan (1996). Hemistena lata. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on February 1, 2010.
2. ^ ^{a b c} Parmalee, P. W. and Bogan, A. E. (1998) The Freshwater Mussels of Tennessee. Knoxville, TN: University of Tennessee Press.
3. ^ C. J. Moseley, ed (1990). "Cracking Pearly Mussel". The Official World Wildlife Fund Guide to Endangered Species of North America. volume III. Washington, D.C.: Beacham Publishing Inc.. pp. 1447–1448. 
4. ^ ^{a b} "Endangered Species: Cracking Pearlymussel (Hemistena lata)". U.S. Fish and Wildlife Service. 1997. http://www.fws.gov/Midwest/endangered/clams/crack_fc.html. Retrieved April 15, 2007. 
5. ^ R. C. Biggins (1991). "Recovery Plan for Cracking Pearlymussel (Hemistena (=Lastena) lata)". http://ecos.fws.gov/docs/recovery_plans/1991/910711.pdf.