Tubercled-blossom Pearly Mussel - Epioblasma torulosa torulosa

Kingdom Animalia Tubercled-blossom Pearly Mussel

Photo: a shell of the Tubercled-blossom Pearly Mussel (Epioblasma torulosa torulosa). The shell is photographed by the U.S. Fish and Wildlife Service. This image is created by Peter Maas for The Sixth Extinction Website and has been released under the Creative Commons Attribution Non-commercial No Derivatives 3.0 licence.

Phylum Mollusca
Class Bivalvia
Order Unionoida
Family Unionidae
Genus Epioblasma
Species Epioblasma torulosa
Subspecies Epioblasma torulosa torulosa
Authority (Rafinesque, 1820)
TSEW Status Extinct (EX), Year assessed: 2010
IUCN Status Extinct (EX), Year assessed: 2000
English Name Tubercled-Blossom Pearly Mussel, Tuberculed Riffle Shell, Tubercled Blossom
Dutch Name Geknobbelde Parelmossel

See image.


This mussel's reproduction required a stable, undisturbed habitat and a sufficient population of host fish to complete the mussel's larval development. When the male discharged sperm into the current, females downstream siphon in the sperm in order to fertilize their eggs, which they stored in their gill pouches until the larvae hatched. The females then expelled the larvae. Those larvae that managed to attach themselves to the gills of a host fish grew into juveniles with shells of their own. At that point they detached from the host fish and settled into the streambed, ready for a long (possibly up to 50 years) life as an adult mussel. 

Range & Habitat

This freshwater mussel occurred in Canada and the United States (Alabama, Illinois, Indiana, Kentucky, Ohio, Tennessee, West Virginia). This mussel was found in large rivers, in shallow sand and gravel shoals with rapid current.

History & Population This mussel was once quite abundant throughout all the major rivers of its range. It was particularly numerous in the Ohio River Valley. The last individual collected was a freshly dead one found below Kanawha Falls, West Virginia (USA) in 1969. There have been no sightings since. 
Extinction Causes

Damming on river systems, dredging and creation of navigation pools has led to destruction of habitat. Deforestation and the spread of intensive agriculture caused an increased turbidity and siltation of the rivers. 

Museum Specimens The Cleveland Museum of Natural History has this subspecies in its collection. Do you know more museums? Contact this website!

Other extinct Epioblasma: Angled Riffleshell (Epioblasma biemarginata), Arc-form Pearly Mussel (Epioblasma arcaeformis), Arcuate Pearly Mussel (Epioblasma flexuosa), Yellow-blossom Pearly Mussel (Epioblasma florentina florentina), Acorn Pearly Mussel (Epioblasma haysiana), Stone's Pearly Mussel (Epioblasma lenior), Lewis Pearly Mussel (Epioblasma lewisii), Fine-rayed Pearly Mussel (Epioblasma personata), Nearby Pearly Mussel (Epioblasma propingua), Sampson's Pearly Mussel (Epioblasma sampsonii), Steward's Pearly Mussel (Epioblasma Stewardsonii), Green-blossom Pearly Mussel (Epioblasma torulosa gubernaculum), Turgid-blossom Pearly Mussel (Epioblasma turgidula).


IUCN Red List of Threatened Species: Epioblasma torulosa ssp. torulosa.

Freshwater Mollusk Conservation Society

References Bogan, A.E. 2000. Epioblasma torulosa ssp. torulosa. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.2. <>. Downloaded on 17 August 2010.
Citation: Maas, P.H.J. (2010).Tubercled-blossom Pearly Mussel - Epioblasma torulosa torulosa. In: TSEW (). The Sixth Extinction Website. <>. Downloaded on .
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Updated: 17 August 2010


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