Scientific Name: Elliptio dilatata

Classification:  State Special Concern

Photo Credit: NCWRC




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

The spike is a large, elongate, dark-chocolate brown freshwater mussel. The posterior ridge is well rounded and close to the dorsal margin. Both the anterior and posterior ends are rounded. In younger individuals, the periostracum is a lighter tan color with narrow green rays extending over the entire surface. In the right valve, the more posterior pseudocardinal tooth is large and prominent; while the more anterior pseudocardinal tooth is vestigial. The lateral tooth in the right valve is large and prominent especially toward the posterior end. Both pseudocardinal teeth and the two lateral teeth are prominent in the left valve. The anterior adductor muscle scars are well impressed; however, the posterior adductor muscle scars are present but less impressed. The pallial line is distinct. The color of the nacre is a rich deep purple.


Shell Anatomy


As described by Burch (1973), the spike has an extensive range throughout the entire Mississippi Drainage Basin and extends into the St. Lawrence Drainage Basin and into the Alabama Drainage Basin in Florida and into Texas in the Guadalupe Drainage Basin. Distribution by County: New River Basin: Alleghany Co. (New River); Ashe Co. (North Fork New River, South Fork New River, New River); Watauga Co. (South Fork New River). Tennessee River Basin: Cherokee Co. (Hiwassee River); Macon Co. (Little Tennessee River); Swain Co. (Little Tennessee River). (Little Tennessee River). NOTE: All headwater areas that flow into these occupied habitats should receive special management.


In the Little Tennessee River, specimens have been taken from most substrate types—sand, gravel, and mixed sand/gravel/cobble. The spike is found in small to large rivers where it may be locally common (Ahlstedt 1984; Gordon and Layzer 1989). Other biologists have also found the spike in various substrates down to about 3 meter depths (Ortmann 1919; Baker 1928; Parmalee 1967).

Ortmann (1919) observed the spike to be a short-term breeder (tachytictic). Gravid females have been found from April through September. On occasion, the spike may be hermaphroditic (van der Schalie 1970). Wilson (1916) identified gizzard shad (Dorosoma cepidianum) as one fish host for the spike. Additionally, Howard (1914) identified flathead catfish (Pylodictus olivaris), white crappie (Pomozis annularis), and black crappie (Pomoxis nigromaculatus) as fish hosts.


General Life History For Mussels