NEM 10V Lecture Notes - Lecture 31: Mollusca, Radula, Cephalopod
Nematology
Part 5 Mollusca (Sea Shells):
• Mollusks are separated into 3 categories.
• Gastropods are snails and slugs.
• Clams, oysters, mussels, and scallops are Bivalves with a hinged two-part shell.
Cephalopods propel themselves by jet propulsion, and include octopus, squid, cuttlefish
and nautilus.
• All mollusks have a mantle that is a skirtlike extension of the body capable of secreting a
shell.
• For feeding, gastropods and cephalopods have a rasping tongue like organ called the
radula.
• Bivalves are filter feeders.
• Aquatic mollusks have gills for respiratory organs. Land-dwelling gastropods have a
lung.
• Slugs secrete slime that is a liquid crystal.
• Rather than being a liquid or a solid, molecules in slime are aligned with their neighbors
and can move and flow together.
• Slime can be either a lubricant or an adhesive allowing slugs to either glide over or to
stick to surfaces.
• Cephalopod means “head-footed,” and their foot has been modified into tentacles and/or
arms that extend from the head.
• All cephalopods are predators and most have beaklike, biting mouthparts, in addition to a
radula.
• Cephalopods exhibit greater intelligence than other invertebrates.
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