Encyclopedia Dubuque
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Affiliated with the Local History Network of the State Historical Society of Iowa, and the Iowa Museum Association.
FAWNSFOOT
FAWNSFOOT. Found in large rivers or the lower reaches of medium-sized rivers in sand or gravel, the fawnsfoot has historically been widespread and very common. By 2000 the numbers of the species were considered lower. It may be overlooked because of its small size, 1.25-1.75 inches.
For most of their lives, mussels are filter feeders that live buried in the sediments of permanent rivers or lakes. Mussels burrow into the ground of the stream and can move around slowly with the use of their foot, a hatchet-shaped muscle that is extended out between the valves. A mussel will insert its foot into the sediment and then contract it to pull itself along the bottom of its aquatic habitat. Mussels frequently live in dense aggregations called “mussel beds” that contain 10-30 different species.
Mussels eat by filtering out small, organic particles including bacteria, algae, and fungus from the water. They draw in water through an incurrent siphon, remove food and oxygen with their gills, and expel the water and waste through their excurrent siphon. Food particles are carried to the mussel's mouth by tiny, hair-like cilia on the gills (Cummings and Graf 2014).
Like all native mussels, the Fawnsfoot has a complex and distinctive life cycle [BS2]. Fertilized eggs are brooded in the female's outer gills, where they develop into tiny clam-shaped larvae called “glochidia”. To complete development, the glochidia must attach to the gills or fins of a suitable host fish. While attached to the host, the glochidia undergo an anatomical change where adult structures develop including paired adductor muscles, gills, a foot, and a digestive system. When juveniles are fully developed, they release from the fish, fall to the substrate, and begin life as free living mussels. (1)
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Source:
1. Rare Species Guide, Minnesota Department of Natural Resources, Online: https://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=IMBIV45020