Villosa iris

Villosa iris, the rainbow mussel or rainbow-shell, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. In 2018, Watters proposed to move the species into a new genus, Cambarunio.

Reproduction
All Unionidae are known to use the gills, fins, or skin of a host fish for nutrients during the larval glochidia stage. Female villosa iris attract host fish by imitating a crayfish. Elongate papillae on the mantle margin resemble antennae, legs, and eyes. They also mimic crayfish behavior, moving the papillae independently like legs, and use "tail tucking" motions. Juvenile mussels bury in the sediment just below its surface, and feed on bacteria and bacterial-sized particles including algae.

Distribution
This species is widely distributed throughout the St. Lawrence, upper Mississippi, Ohio, Tennessee, and Cumberland River Basins.

Conservation status
Villosa iris is the focus of conservation concern in areas like Ontario, Illinois, West Virginia, Pennsylvania and Wisconsin. In Canada, V. iris is listed as a species of Special Concern by COSEWIC and under the Species at Risk Act, having been downgraded to this status in 2019 after its initial listing as Endangered in 2013. In Wisconsin, it is listed as state endangered.