What is a Mollusk? Soft body with internal or external shell Ex: snails, slugs, clams, squids, and octopi Trochophore larva
Body plan: Foot – takes on many forms Mantle – covers the body Shell – (present in most), made by glands in the mantle Visceral mass – internal organs
Feeding: Herbivores, Carnivores Filter feeders (clams, Oysters, scallops) Parasites Many feed using a flexible tongue shaped structure called a radula. (snails, slugs)
Respiration: Aquatic mollusks – snails, clams – breathe using gills in the mantel cavity Land snails breathe with a “lung” – a mantle cavity with a large surface area and many blood vessels.
Circulation – can be open or closed Open works better for slow moving mollusks (less efficient) Closed works better for fast moving mollusks (more efficient) Excretion – tube shaped nephridia Response – nervous systems vary from simple to complex Reproduction – many reproduce sexually with external fertilization, Tentacled mollusks this is usually internal A few are hermaphrodites All have a free swimming trochophore larva !
Groups of Mollusks Three major classes of mollusks 1. Gastropods 2. Bivalves 3. Cephalopods
Gastropod snails, slugs, and nudibranchs Shell-less or single shelled Move by a muscular foot Some are poisonous, bright colors