Marine biologists have long thought that variation in the shell color of aquatic snails evolved as protective camouflage against birds and other predators. Brown shells seem to be more frequent when the underlying seafloor is dark-colored and white shells more frequent when the underlying seafloor is light-colored. A new theory has been advanced, however, that claims that shell color is related to physiological stress associated with heat absorption. According to this theory, brown shells will be more prevalent in areas where the wave action of the sea is great and thus heat absorption from the Sun is minimized, whereas white shells will be more numerous in calmer waters, where the snails will absorb more heat from the Sun’s rays.
Evidence that would strongly favor the new theory over the traditional theory would be the discovery of a large majority of