Anatomy

Mollusks are triploblastic protosomes which have evolved for life in both sea and land. Almost all Mollusks have four basic parts in common. These are the foot, shell, mantle, and visceral mass. The foot, despite being called a foot, is used for feeding in many species and contains the mouth. The muscular foot is also used for movement in most species, and it has evolved to be a burrowing, crawling, and prey capturing organ. The shell, which is secreted by cells is the mantle, is composed primarily of Calcium Carbonate, but also contains other organic compounds in its' many layers. Beneath the shell and mantle can be found the visceral mass. This part of the Mollusk contains the internal organs, which necessitates protection by the shell. An organ found only in Mollusca and nowhere else on the invertebrate family tree is the radula. It is a tongue like organ with many tiny sharp teeth running along it. The Radula has evolved to suit species with different feeding styles. In herbivores, it is used to scrape algae from rocks and in some carnivores, to drill through the hard shell of prey.