Mollusks are divided into six classes: gastropoda, monoplacophores, polyplacophores, scaphopods, bivalves and cephalopods. Despite their distinct appearances, they are all structurally similar with three body regions and sometimes a shell or a tongue, called a radula.
Gastropoda contain over 50,000 species, found both in water and on land. They can be recognized by their colors and spiral structures. Although monoplacophores are as old as Gastropoda, they reach only an inch in length and are found primarily on seabeds. Polyplacophores, also known as chitons, live just below the surface on reefs. Their shells are made up of eight tiny plates layered on top of one another. Scaphopods first washed up on the shores 550 million years ago. They reach a maximum length of 5 inches and are usually white in color. They appear to be small, white, curved tubes. Bivalves, like clams, consist of two hinged plates that protect the organism living inside and can be found in both seawater and freshwater habitats. Cephalopods include creatures like giant squids and octopods. Considered the most evolved of the mollusks by Sanibel History, cephalopods are carnivorous with well-developed nervous systems and internal shells. Cephalopods have excellent eyesight and parrot-like beaks that they use to catch and devour their prey.