''Epioblasma torulosa'', commonly called the tubercled blossom, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs ...

, a

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Unionidae The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is at its most divers ...

. It is native to eastern North America, where it is considered endangered in both Canada and the United States.

Natural history

This species is known from the Cumberland,

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

St. Lawrence Saint Lawrence or Laurence ( la, Laurentius, lit. " laurelled"; 31 December AD 225 – 10 August 258) was one of the seven deacons of the city of Rome under Pope Sixtus II who were martyred in the persecution of the Christians that the Roma ...

, and

Tennessee River The Tennessee River is the largest tributary of the Ohio River. It is approximately long and is located in the southeastern United States in the Tennessee Valley. The river was once popularly known as the Cherokee River, among other name ...

drainages. It is found in shallow riffle zones over sand and gravel in large to medium sized rivers. Due to

habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

siltation Siltation, is water pollution caused by particulate Terrestrial ecoregion, terrestrial Clastic rock, clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the ...

, and other factors, two out of the three subspecies are now extinct. The surviving subspecies is considered highly imperiled, with only three known locations showing evidence of reproduction.NatureServe
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Subspecies

This species exhibits variable shell characteristics across its geographic range. It is unclear whether this is best understood as

ecophenotypic variation Ecophenotypic variation ("ecophenotype") refers to phenotypical variation as a function of life station. In wide-ranging species, the contributions of heredity and environment are not always certain, but their interplay can sometimes be determin ...

, various subspecies, or a complex of closely related but genetically isolated species. Due to the extinction of three of the four subspecies often included, resolution of this question will be difficult. The most modern approach is to treat ''E. torulosa'' as a species with three subspecies, and separate out the closely related ''

Epioblasma cincinnatiensis ''Epioblasma'' is a genus of freshwater mussels, aquatic bivalve mollusks in the family Unionidae, the river mussels. Most of the species in this genus have been lost in modern times, and the entire genus is threatened with the possibility of e ...

'' as a full species. * Green blossom (''Epioblasma torulosa gubernaculum''): Extinct. Known from the headwaters of the

. *

Northern riffleshell The northern riffleshell (''Epioblasma torulosa rangiana''), is a subspecies of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. This subspecies is endangered. This species was formerly found widely i ...

(''Epioblasma torulosa rangiana'') * Tubercled blossom (''Epioblasma torulosa torulosa''): Extinct. Known from the main stem of large rivers.

References

torulosa Taxa named by Constantine Samuel Rafinesque ESA endangered species {{Unionidae-stub