SupportThese animals are soft-bodied animals that usually have a shell either inside or outside of the body.
HabitatThere are a wide range of mollusks that live in very different habitats; marine and terrestrial.
Juvenile MollusksMany aquatic mollusks have a free-swimming larval stage. This is called a trochophore larva.
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Response to StimulusThere is great variation in the complexity of mollusk nervous systems. Clams and other two-shelled mollusks have simple nervous systems consisting of ganglia. Squid and octopus, however, have the most highly developed nervous system of all invertebrates.
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FeedingMollusks are herbivores, carnivores, filter feeders, detritovores, or parasites. Many mollusks feed with a radula, to which hundreds of tiny teeth are attached. Many, like octopus and squid have sharp jaws. Bivalves, like clams and oysters, are filter feeders and use a siphon to move water into the body.
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Reproduction/Life CycleAll mollusks reproduce sexually. Many snails and two-shelled mollusks exhibit external fertilization. Tentacled mollusks use internal fertilization inside the female.
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MovementSnails secrete mucus that helps them glide along rough surfaces, using their foot to push them along. Octopus and squid use a form of jet propulsion.
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Body PlanThe plan of most mollusks have four main parts:
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RespirationAquatic mollusks use gills inside their mantle cavity. Land snails and slugs don't have gills, but they use their thin mantle cavity with a large surface area covered in blood vessels. This is sometimes called a lung, but it is NOT as developed as a true lung. They need to be in a moist environment.
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ExcretionMuch like oligochaete, mollusks have tube-shaped nephridia to remove ammonia.
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CirculationMollusks have either an open or closed circulatory system. Open circulation means that blood is pumped through vessels by a simple heart, and eventually leaves the vessels and works it way through different sac-like sinuses.
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Class Cephalopoda
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