What are some possible adaptive values of the shell-within an aquatic environment?
1) Protection from predators 2) Energy conservation in locomotion 3) providing fixed sites for muscle attachment 4) Storage of excess calcium 5) A waste product sink 6) support to raise the body above the sea floor (facilitate food gathering) 7) built-in channeling of water currents The mollusc epidermis is specialized in a number of other ways as well. There are patches on the epidermis that are ciliated allowing for locomotion and movement of water currents for feeding, respiration etc. Although molluscs are often covered with a hard secreted structure, they themselves are soft. The alternation of circular and longitudinal muscles is reduced and other muscles are more prevalent-allowing for more complex movement patterns. From an evolutionary standpoint, the mollusc body wall is very plastic. To a far greater extent than in most animals, the body wall is involved in locomotion. So we know that arthropod and annelid diversity may largely be attributed to metamerism, and the exoskeleto
