BIO2231 Chapter Notes -Coelom, Odontophore, Veliger
Document Summary
Molluscs are coelomate lophotrochozoan protostomes, and as such they develop via spiral mosaic cleavage and make a coelom by schizocoely. The ancestral larval stage is a trochophore, but development is variously modified within the classes. The coelom in molluscs is limited to a space around the heart, and perhaps around the gonads and part of the kidneys. Although it develops embryonically in a manner similar to the coelom of annelids, the functional consequences of this space are quite different because it is not used in locomotion. Reduced to its simplest dimensions, the mollusk body plan may be said to consist of a head-foot portion and a visceral mass portion. The head-foot is the more active area, containing the feeding, cephalic sensory, and locomotor organs. It depends primarily on muscular action for its function. The visceral mass is the portion containing digestive, circulatory, respiratory, and reproductive organs, and it depends primarily on ciliary tracts for its functioning.
