Crayfish, also known as crawfish, crawdads, freshwater lobsters, mountain lobsters, or mudbugs, are freshwater crustaceans resembling small lobsters, to which they are related; taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some species are found in brooks and streams where there is running fresh water, while others thrive in swamps, ditches, and rice paddies. Most crayfish cannot tolerate polluted water, although some species such as Procambarus clarkii are hardier. Crayfish feed on living and dead animals and plants.