North Carolina Wildlife Resources Commission

Tar River Spinymussel (R.I. Johnson and Clarke, 1983)

Scientific Name: Elliptio steinstansana

Classification:  Federal and State Endangered

Photo Credit: NCWRC
   

Interior

 

Exterior 

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

The Tar River spinymussel was first described by Johnson and Clarke (1983). Shells rarely exceed 55 mm in length. Clean young shells are shiny, usually yellowish-brown, and rayed. Older shells become brownish and tend to lack rays.

One or two rows of spines are usually associated with the posterior ridge. Up to six spines may be present on each valve. Spines rarely exceed 5 mm in length. The posterior ridge is rounded. The shell is thickened toward the anterior end. Lateral and pseudocardinal teeth are present in each valve. The nacre is iridescent toward the posterior end and salmon to cream colored toward the anterior end. The nacre has narrow linear raised ridges extending from the umbo to the ventral margin under the posterior ridge. The incurrent and excurrent apertures and their associated papillae are usually white to cream colored. Papillae are simple (not branched). The foot and other organs may be salmon to cream colored.

Tar River spinymussel

photo by Ken Taylor 

 

Shell Anatomy

 
Distribution by County: Neuse River Basin: Johnston Co. (Little River Subbasin); Tar River Basin: Franklin Co. (Shocco and Sandy creek subbasins), Nash Co. (Swift Cr. Subbasin and Tar River), Halifax Co. (Little Fishing Cr. Subbasin), Edgecombe Co. (Swift Cr. Subbasin, Tar River). NOTE: All headwater areas that flow into these occupied habitats should receive special management.

 


This species is most closely associated with unconsolidated beds of coarse sand and gravel in relatively fast flowing water. Stream banks are stable with extensive root systems holding soils in place. The associated landscape is largely wooded, especially near streams. Trees near the stream are relatively mature and tend to form a closed canopy over smaller streams, creeks, and headwater river habitats. Water quality is good to excellent.

Maximum age for the Tar River spinymussel is around twelve years. The species is a tachytictic breeder. Females become gravid in late May to early June, and glochidia are released by the end of June. Fish hosts are unknown. However, if the James spinymussel is closely related to the Tar River spinymussel (highly probable), the fish hosts probably include rosyside dace, bluehead chub, rosefin shiner, satinfin shiner, and swallowtail shiner. This is based upon Hove's (1990) work with the James spinymussel.

 

General Life History For Mussels