North Carolina Wildlife Resources Commission

Oyster Mussel (Lea, 1834)

Scientific Name: Epioblasma capsaeformis

Classification:  State Extirpated

Photo Credit: NCWRC
   

Female Interior

 

Female Exterior 

     

 

Male Interior

 

Male Exterior

NOTE: Hover over the bold words for definitions or see the Glossary.

This species was described by Isaac Lea in 1834 from the Cumberland River in Tennessee. The oyster mussel is a small species (adults 50 - 70 mm) that exhibits pronounced sexual dimorphism (male and female shells differ in form). The periostracum is yellowish-green with numerous narrow green rays, and the nacre is bluish-white to creamy in color. Male shells are elliptical in shape; while, female shells have a swollen posterior end that is dark green in color. The species has two lateral teeth in the left valve and one lateral tooth in the right valve. Two small pseudocardinal teeth are present in each valve.

 

Shell Anatomy

 
The oyster mussel was once one of the most widely distributed Cumberlandian mussel species. The mainstem Cumberland and Tennessee Rivers, as well as many tributaries, harbored this species. The species has been extirpated from much of its range, and only a few populations still exist in Cumberland River tributaries.

Historic Distribution in North Carolina: French Broad River

 


The oyster mussel inhabits medium-size streams to large rivers on shoals and riffles in course sand/gravel/cobble substrate. It is not associated with small stream habitats and does not extend far upstream in tributaries. It prefers water depths of less than three feet and is sometimes found associated with water-willow (Justicia americana) beds.

This species is a bradytictic breeder. Spawning occurs in late summer, and gravid females have been observed in May through July. Females have been observed lying on top of the substrate while displaying soft parts. Identified fish host species include spotted, redline and dusky darters, and banded sculpin.

 

General Life History For Mussels