 Class Gastropoda (Stomach-Foot)  Examples: Snails, Slugs, Nudibranchs  Class Bivalve (Two-Hinge)  Examples: Clams, Oysters, Scallops  Class Cephalopods (Head-Foot)  Examples: Squid, Octopus, Nautilus

 Symmetry: Mollusks are bilateral, except snails which are asymmetrical due to their shell.  Body Openings: Two (mouth & anus)

All mollusks possess three structures:  Head/Foot Head = Brain or Sense Organs Foot = Movement  Visceral Mass Internal Organs (Mollusks possess simple digestive, excretory, nervous, cardiovascular, and reproductive systems)  Mantle Layer of tissue that secretes calcium carbonate to form a shell

 All mollusks reproduce sexually.  Most often external fertilization & development.  Gastropods are hermaphrodites.  Cephalopods undergo complex mating rituals.  Mollusks obtain food in many ways.  Herbivores, carnivores, filter feeders, detritus feeders, and parasites.  Radula  A tongue-shaped structure used to carve through prey.

 Environmental   Mollusks clean the water as they filter feed.  Food for other organisms (food chains).  Delicacies   Oysters, clams, snails, escargot, pearls/jewelry  Science   The shells of are used as a source of calcium in dietary supplements.  Medicine

Bivalves:  Most bivalves are capable of making pearls when foreign substances enter their shell. They coat the foreign substance with the same as the lining of their shell. Some mollusks can grow pearls as big as golf balls. It takes a commercial pearl oyster about two years to grow big enough to be of use to us as jewelry. Pearl Harvesting Video Clip  The largest known bivalve is a "Giant Clam" which weighed in at an amazing 734 pounds and was nearly four feet in length. The shells of this beast were often used as children's bath tubs, and for baptismal fonts in many churches. Growing A Giant Clam Video Clip

Gastropods:  The common garden snail can travel about two feet in three minutes. At that rate, it would travel one mile in five and one-half days!  Slime is important for:  Movement: Slugs use slime, as well as suction power, to travel upside down and up trees and other vertical things.  Defense: When in danger, the slug is able to emit a thick mucus coating, making it more difficult to eat them, as well as an unpleasant taste.  Reproduction: Mating rituals of banana slugs take place in a thick blanket of slime.  Nutrition: Slugs have been seen eating slime and debris collected at their tails. It is possible that slime could have a nutritional purpose.  All cone shells possess a poisonous dart with which they harpoon, inject venom and thus kill their prey. Some cone shell possess venom so toxic that if stung, it can seriously hurt or even kill a full-grown man! Poison In A ConePoison In A Cone  Many land snails can lift ten times their own weight up a vertical surface. (If you were this strong, you could carry almost 700 pounds straight up a wall!)

Cephalopods:  One of the most intelligent of all invertebrates.  Cephalopods can change color better than a chameleon.  Use jet propulsion and tentacles for movement.  Are able to move on land for short periods of time.  Octopus & Squid Video Clips Octopus & Squid Video Clips  You Tube You Tube

1. We mentioned in class that mollusks are considered tasty treats in many countries. If you are brave enough, go to the following website: Type in Eating Live Octopus and watch the 4:00 min. clip. That is one cephalopod menu item. Name one more cephalopod that can be eaten, along with three more mollusk menu items…at least one gastropod and at least one bivalve. 2. Most mollusks are named according to the location of their muscular foot used for movement. If humans were classified as mollusks, what do you think would be their name? (You can make up a new one if needed). What about dogs? And what about snakes?