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Anodonta nuttalliana Lea 1838
Winged Floater
Family: Unionidae
Species account authors: Ethan Jay Nedeau, Allan K. Smith, Jen Stone, and Sarina Jepsen.
Extracted from Freshwater Mussels of the Pacific Northwest, 2nd Edition (2009)
© Xerces Society for Invertebrate Conservation.
Introduction to the Molluscs of BC

Photograph

© Ian Gardiner     (Photo ID #80519)

Map

E-Fauna BC Static Map

Distribution of Anodonta nuttalliana in British Columbia in British Columbia

Species Information

Size: Up to five inches.

Shape: Elliptical or ovate; L:H ratio usually less than 1.5. Valves laterally inflated but this trait is variable. Valves slightly to moderately compressed to­ward the posterior dorsal margin, broad, and raised to form a “wing”. The prominence of the wing is variable. Valves are thin and fragile. Beaks Small; scarcely elevated above the hinge line.

Periostracum: Color is variable, with individuals appearing yellowish-green, yellowish-brown, olive, pale brown, reddish brown, or black. There are greenish rays on the posterior slope. The periostracum is smooth and growth lines are prominent.

Hinge Teeth: None.

Nacre: Usually white, but sometimes with a flesh-colored, purplish, or bluish tint.

For a discussion on Anodonta taxomony, please refer to the original publication, The Freshwater Mussels of the Pacific Northwest.

Biology


More research is needed to understand the specific life history of this clade. Like other Anodonta, they are thought to be fast-growing species that reach sexual maturity in four to five years and live only ten to 15 years. Host fish are unknown.

Habitat


Preferred habitats include shallow muddy or sandy habitats in slow rivers and lakes, though they are also known from some reservoirs. They can inhabit streams and rivers but usually are found in stable areas with fine sedi­ments and little shear stress.

Distribution

Global Distribution

Given the recent taxonomic work suggesting that A. californiensis and A. nuttalliana belong to a single clade, it is difficult to denote the range of these “species” in western North America. The native range of what has been called A. californiensis extended from Baja California to southern British Columbia, and east to western Wyoming, eastern Arizona, and Chihuahua (Mexico). It was originally widespread in California, but its distribution is now greatly reduced. It was once distributed throughout six major drainages in Arizona, but today only remnant populations are thought to exist in portions of the Black River drainage and Little Colorado River. In Washington, recent records are mainly from the Columbia River drainage. A. nuttalliana had been considered the least common western Anodonta. Even before the recent genetic work was published, people had difficulty identifying this species and historical data are difficult to assess because A. nuttalliana was often called by other names. One reason for the confusion is that specimens of A. nuttalliana with a low dorsal wing are nearly indistinguishable from A. californiensis.
Distribution in British Columbia

In British Columbia this species is known from the lower mainland to the east Kootenays and north to Lac la Hache (Gelling 2008).

Conservation

Conservation Concerns

Mussels rely on fish to reproduce and replenish populations; and therefore changes in the West’s fish fauna have threatened the region’s mussel fauna. This species has historically been affected by water diversion for irrigation, water supply, and power generation. They have been found in reservoirs, but many reservoirs experience severe annual water level fluctuations that decimate the standing crop of mussels during low-water periods. Non-native fish may compete with a mussel’s host fish, or eat young mussels (e.g., common carp), and nonnative mollusks can compete with mussels for food and space (e.g., Asian clams, zebra mussels, and quagga mussels). Mussels are sensitive to water quality changes, habitat changes as well as changes in the fish fauna.

Comments


The Unionidae are distributed throughout the world, but are most diverse in eastern and central North America, and in China and Southeast Asia.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
UnlistedUnlistedUnlistedUnlisted



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