Crawfish (crayfish); photo by Alan Goodman on Flickr (noncommercial use permitted with attribution / share alike).
Official State Invertebrate of Missouri
Missouri designated the crayfish (also called crawfish or crawdad) as the official state invertebrate in 2007. The crayfish was nominated for state invertebrate by Mrs. Janna Elfrink's elementary school class (Reeds Spring, Missouri). All State Fish & Aquatic-Life Symbols
The crayfish resembles a very small lobster. Coloring varies depending on the water it lives in. Missouri has more than 30 species of crayfish (including seven species that occur nowhere else in the world). Crayfish are considered a "keystone species" because they play a key role in aquatic ecosystems.