Basis for Listing

The yellow sandshell was coveted by the pearl button industry because of its beautiful smooth white nacre (inner shell) and evenly thick shell. In Minnesota, it occurred primarily in the main-stem Mississippi and Minnesota rivers (Dawley 1947; Bright et al. 1990). This species is sometimes split into two subspecies or morphotypes: a rayed, generally smaller river morph (Lampsilis teres teres, slough sand shell) and a rayless, mostly big-river morph (L. t. anodontoides, yellow sand shell) (Parmalee 1967; Oesch 1984). Both forms were historically common in the upper Mississippi River (van der Schalie and van der Schalie 1950), however no live specimens have been collected from Minnesota waters in recent decades. It is now one of the rarest mussels in Minnesota. Given its extreme rarity, the yellow sandshell was listed as an endangered species in Minnesota in 1996.

  Description

The yellow sandshell has a smooth stout and elongate shell that can reach up to 13 cm (5 in.) long. The exterior of the shell is yellow, occasionally with green rays, and shiny, especially in young mussels. The posterior end of the shell is pointed in males and somewhat truncate in females. The beak sculpture consists of fine and closely spaced wavy ridges. The pseudocardinal and lateral teeth are well-developed, and the inner shell is white. The yellow sandshell resembles the black sandshell (Ligumia recta), the fat mucket (Lampsilis siliquoidea), and the pondmussel (L. subrostrata). The yellow sandshell's beak sculpture and color distinguish it from the black sandshell, its elongate and narrow shell distinguish it form the fat mucket, and its color, size, and thickness distinguish it from the pondmussel.

  Habitat

In Minnesota, the yellow sandshell inhabits large sized rivers. As its name implies, it is at home in fine sediments, but it may also occur in coarse substrates, and in slow or moving current (Parmalee and Bogan 1998).

  Biology / Life History

Mussels are long-lived animals. Members of many species may live for several decades and in some instances, a century or more. They spend most of their lives buried in the bottom sediments of permanent water bodies, and often live in multi-species communities called mussel beds (Sietman 2003).

Mussels are primarily sedentary, but they can move around with the use of their foot, which is a hatchet shaped muscle that can be extended out between the valves (shells). A mussel will burrow its foot into the sediment and then contract it to pull itself slowly along the bottom of its aquatic habitat (Sietman 2003).

Mussels eat by filtering bacteria, protozoans, algae, and other organic matter out of the water. They draw water into their body through their incurrent siphon, remove food and oxygen with their gills, and then expel the filtered water through their excurrent siphon. Food particles are carried to the mussel's mouth by tiny hairlike cilia located on the gills. Waste is expelled through the excurrent siphon (Sietman 2003).

Mussels have a complex and distinctive reproductive cycle. Males release sperm into the water, which are drawn in by females through their incurrent siphon. Fertilized eggs are brooded in the female's gills, where they develop into tiny larvae called glochidia. Baker (1928) reports that the yellow sandshell is bradytictic, with females brooding their young over winter before they are released as glochidia. Once the glochidia are expelled from the female's gills, they attach to fish gills or fins by clamping onto them with their valves. The glochidia live as parasites on the host fish until they develop into juvenile mussels, at which point they detach from the fish and fall to the streambed as free-living mussels. The shovelnose sturgeon (Scaphirhynchus platorynchus), longnose gar (Lepisosteus osseus), shortnose gar (L. platostomus), largemouth bass (Micropterus salmoides), green sunfish (Lepomis cyanellus), orangespotted sunfish (L. humilis), warmouth (L. gulosus), black crappie (Pomoxis nigromaculatus), and white crappie (P. annularis) have been reported to be viable fish hosts for the glochidia of the yellow sandshell (Watters 1994).

  Conservation / Management

The viability of remaining populations of the yellow sandshell in Minnesota is jeopardized by the continuing decline in habitat conditions on the Mississippi River associated with its management as a navigation canal, and with non-point and point source water and sediment pollution. Dams, channelization, and dredging increase siltation, physically alter habitat conditions, and block the movement of fish hosts. The yellow sandshell is also being impacted by the infestation of non-native zebra mussels (Dreissena polymorpha) in the Mississippi River and its tributaries. Zebra mussels can attach themselves in large numbers to the shells of native mussels, eventually causing death by suffocation. In the Minnesota River, land use practices that lead to poor water quality and excessive sediment are the primary factors limiting the yellow sandshell.

  Conservation Efforts in Minnesota

A 10-year statewide mussel survey initiated by the Minnesota DNR in 1999 resulted in a better understanding of the yellow sandshell's ecology and current status in Minnesota. A very recently dead shell was found in the lower Minnesota River at Pike Island near the confluence with the Mississippi River in 2000 (M. Davis, Minnesota DNR, pers. comm.), giving hope that this species may still be extant there. Additionally, efforts are underway to propagate juvenile yellow sandshells for restocking into areas where habitat conditions have improved.

  References and Additional Information

Baker, F. C. 1928. The fresh water mollusca of Wisconsin: part II: Pelecypoda. Wisconsin Geological and Natural History Survey Bulletin No. 70, Part II. University of Wisconsin, Madison. 495 pp.

Bright, R. C., C. Gatenby, D. Olson, and E. Plummer. 1990. A survey of the mussels of the Minnesota River, 1989. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 106 pp.

Dawley, C. 1947. Distribution of aquatic mollusks in Minnesota. American Midland Naturalist 38:671-697.

Oesch, R. D. 1984. Missouri naiades: a guide to the mussels of Missouri. Missouri Department of Conservation. Jefferson City, Missouri. 270 pp.

Parmalee, P. W. 1967. The fresh-water mussels of Illinois. Illinois State Museum, Popular Science Series 8. 108 pp.

Parmalee, P. W., and A. E. Bogan. 1998. The freshwater mussels of Tennessee. The University of Tennessee Press, Knoxville, Tennessee. 328 pp.

Sietman, B. E. 2003. Field guide to the freshwater mussels of Minnesota. Minnesota Department of Natural Resources, St. Paul, Minnesota. 144 pp.

van der Schalie, H., and A. van der Schalie. 1950. The mussels of the Mississippi River. American Midland Naturalist 44:448-464.

Watters, G. T. 1994. An annotated bibliography of the reproduction and propagation of the Unionoidea (Primarily of North America). Ohio Biological Survey Miscellaneous Contributions No. 1, Columbus, Ohio. 158 pp.