Mollusks

Characteristics: These animals all have a muscular foot (found in a variety of forms) and some form of internal or external shell. There are three main classes: Gastropods (snails, slugs), Pelecypoda (bivalves) and cephalopods (squids/octopods) (examples are shown above in order)

Gastropods: Muscular foot produces slime to aid in locomotion. Many advanced organ systems, both sexes, and specialized structures for breathing (gills in water forms, a lung or sorts for terrestrial forms). The circulatory system is open with a two chambered heart pushing blood around the coelom. The respiratory structures have blood vessels associated with them. The blood is blue because copper is the basis of the hemocyanin pigment. Gastropods use a radula for feeding (its like a tongue that has sharp projections on it). The life cycle of all gastropods include a trochophore larva stage. Some times this is free swimming, may remain in the eggs.

Bivalves: Hinged shell that is produced to ward off predators. The foot is specialized for burrowing. Bivalves breathe using gills; the gills also filter food. Food particles are captured by mucus and pushed by cilia towards the mouth.

Cephalopods: Often thought of as the most intelligent invertebrates. They have a very advanced brain and nervous system, keen vision and tentacles with great tactile ability. Metabolic rates are high and these mollusks have a closed circulatory system. They can swim using fins or are jet propelled. They have beak like teeth for feeding.

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