COSEWIC Status Reports

COSEWIC Assessment and Status Report on the Rainbow Villosa iris in Canada

Rainbow is a small freshwater mussel (average length in Canada about 55 mm) with a compressed, elongate-elliptical shape. The shell is yellowish, yellowish-green, or brown (in old specimens) with numerous narrow and/or wide broken dark green rays that cover the whole surface of the shell. Rays may be absent from the anterior portion of the shell. The nacre (inside of the shell) is silvery white and iridescent, which is the origin of the species’ common name. There are 18 species in the genus Villosa in North America, but only Villosa iris (Rainbow) and Villosa fabalis have ranges that extend into Canada. Only two species in the genus are listed as secure (G5) in North America, one of which is V. iris. Freshwater mussels are sensitive indicators of ecosystem health, including water and habitat quality and the fish community on which they depend. Rainbow may be a particularly good indicator because of its sensitivity to toxic chemicals.

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Contact Person(s)

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment Canada
Ottawa, ON
K1A 0H3
Tel: 819-938-4125
Fax: 819-938-3984
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