Rainbow Shell
Villosa iris (Lea)

Status: State Endangered (August 1, 1989).

Occurence: Occurs in the Mukwonago River. This species may yet be found in rivers of southeastern Wisconsin for which we currently have only historical records. See the species map.

Aid to ID: The shell is elongate and elliptical, relatively thin. The male shell is compressed and the female shell inflated. Females are more expanded in the post-dorsal region and are more broadly rounded, while the male is rather sharply pointed. The beak is small and sculptured with distinctive, double-looped bars. The outer surface is colored yellowish-green to brown with dark green rays. The nacre is silvery white and highly iridescent posteriorly. Shell is small, usually less than 3 inches (7.6 cm).

Habitat: Inhabits small streams, living within and below riffles on a sand, gravel or mud bottom in water less than a meter deep.

Management Considerations: Because this species inhabits small streams, this mussel is most vulnerable to pollution from runoff and siltation. Habitat protection and water quality improvements would benefit this species. Increased development along waterways in southeastern Wisconsin is of great concern for the continued existence of this species.

The content for this page was originally presented in the Endangered and Threatened Invertebrates of Wisconsin, a free publication available by contacting the Endangered Resources Program.