North Carolina Wildlife Resources Commission

Notched Rainbow (Conrad, 1838)

Scientific Name: Villosa constricta

Classification:  State Special Concern

Photo Credit: NCWRC




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

Conrad described this species in 1838. The notched rainbow is a small mussel rarely exceeding 40 mm. Males and females differ in their shell morphology. In males, the the longer end of the shell as measured from the umbo to the margin. In a live animal, the siphons extend from this end is curved from anterior to posterior producing an oval shape; while, in females, the posterior end is expanded to accommodate the marsupium. Also in females, a sulcus is present which ends as a distinct notch along the posterio-ventral margin. In young individuals, the periostracum is golden brown with green rays, and although it may remain so in some populations, generally turns to black with age. There are two pseudocardinal teeth in each valve; however, the anterior tooth in the right valve is not well developed. The lateral teeth are well developed; two in the left valve, one in the right valve. The nacre is typically white to bluish-white and iridescent.


Shell Anatomy


"This species ranges from the Santee-Cooper System [South Carolina] into the James System in Virginia (Fuller 1970)."

Distribution by County: Catawba River Basin: Burke Co. (John's River and Upper Creek). Yadkin River Basin: Mecklenburg Co. (Six Mile Creek); Union Co. (Goose Creek Subbasin); Montgomery Co. (Barnes Creek, Little River Subbasin); Randolph Co. (Little River Subbasin, Barnes Creek, Betty McGees Creek, Carraway Creek, Jackson Creek), Stanly Co. (Big Bear Creek). Cape Fear River Basin: Alamance Co. (Cane Creek, Stinking Quarter Creek); Chatham Co. (Bear Creek, Rocky River); Harnett Co. (Cape Fear River); Orange Co. (Phils Creek); Rockingham Co. (Haw River); Stokes Co. (Dan River). Neuse River Basin: Durham Co. (Deep Creek, North and South Fork Little River, Flat River); Johnston Co. (Little River ,Johnston Co. (Swift Creek)); Nash Co. (Moccasin Creek); Orange Co. (Eno River, North and South Forks Little River); Person Co. (South Fork Flat River, Deep Creek); Wake Co. (Crabtree Creek, Little River, Middle Creek); Wilson Co. (Contentnea Creek, Turkey Creek). Tar River Basin: Franklin Co. (Crooked Creek, Tar River, Fox Creek, Sandy Creek); Granville Co. (Shelton Creek, Tar River); Halifax Co. (Fishing Creek Subbasin, including Little Fishing Creek and Rocky Swamp); Nash Co. (Tar River, Stoney Creek); Vance Co. (Stoney Creek); Warren Co. (Shocco Creek Subbasin, including Little Shocco Creek; Fishing Creek Subbasin, including Long Branch and Little Fishing Creek). NOTE: All headwater areas that flow into these occupied habitats should receive special management.


Fuller (1970) notes that "favored habitat is a clean, sand floor among rocks in the shallows of a smaller, often upland stream, though it will occur in rivers and in mud." In North Carolina, this species is found in streams with sand/gravel substrates, often in stable banks among tree root mats.

Sexual dimorphism in the notched rainbow and the presence of gravid females found during the cooler months of the year confirm that this species is bradytictic. Little else is known of its reproductive biology.  

General Life History For Mussels