Mollusks “Any of numerous chiefly marine invertebrates of the phylum Mollusca, typically having a soft unsegmented body, a mantle, and a protective calcareous shell”

Classification Kingdom: Animalia –Phylum: Molusca There are many different classes of Molluscs (for example, Cephalodopa, Gastropoda, etc…there are 11 total).

Here’s a Picture to Help You Understand Mollusk’s Basic Structure…

Explanation of Mollusk Structure - Soft bodied, but often “protected” by a hard shell. -3 main body sections: 1) a muscular foot that aids in mobility, 2) a visceral mass which holds most of the internal organisms, and 3) a mantle, which is tissue that covers the visceral mass, and creates a shell in snails, clams, etc…sometimes the mantle extends further than the visceral mass and creates a water filled chamber known as the “mantle cavity.” See the next slide for more mollusk anatomy! - Soft bodied, but often “protected” by a hard shell. -3 main body sections: 1) a muscular foot that aids in mobility, 2) a visceral mass which holds most of the internal organisms, and 3) a mantle, which is tissue that covers the visceral mass, and creates a shell in snails, clams, etc…sometimes the mantle extends further than the visceral mass and creates a water filled chamber known as the “mantle cavity.” See the next slide for more mollusk anatomy!

More About Mollusk Structure!  Many mollusks also have a special feature unique to mollusks: the radula  The radula extends from the mouth, and moves back and forth around the mollusk’s environment to facilitate food collection (food consists mostly of algae).  Also, molluks have a circulatory system that “pumps blood and circulates nutrients.” This distinguishes them from flatworms and other organisms to which they can be compared.  Many mollusks also have a special feature unique to mollusks: the radula  The radula extends from the mouth, and moves back and forth around the mollusk’s environment to facilitate food collection (food consists mostly of algae).  Also, molluks have a circulatory system that “pumps blood and circulates nutrients.” This distinguishes them from flatworms and other organisms to which they can be compared.

Mollusks are DIVERSE  Three of the most diverse and interesting groups are  1) Gastropods  2) Bivalves  3) Cephalopods  Three of the most diverse and interesting groups are  1) Gastropods  2) Bivalves  3) Cephalopods

Mollusk Video: Here’s a video that talks more about mollusks’ diversity and anatomy

Gastropods  Largest group of mollusks  Fresh water, salt water, and terrestrial habitats  Single, spiraled shells  Distinct heads, eyes at the tips of long tentacles  Interesting: SLUGS are mollusks! They lost their shell at some point during evolution…why?  Major example of a Gastropod: Land Snails

Bivalves ZHave 2 shells, hinged together ZMantle cavity contains gills, that help in feeding and gas exchange (they have cilia that help “sweep food into the mouth”) ZMost bivalves are sedentary, (live in sand/mud), and use the “foot” for digging and anchoring ZSome examples of Bivalves: clams, oysters, mussels, scallops.

Cephalopods Different from gastropods and bivalves, because their bodies are adapted for “the lifestyle of fast, agile predators.” “Beak-like jaw” and radula helps tear apart prey Big brains! VERY COMPLEX EYES: ex. Octopus eyes have lenses and retinas Octupuses are considered very smart (strong learning abilities) Giant Squid = Largest invertebrate Also, remember the Nautilus from the video in class? It is a mollusk, and has remained UNCHANGED FOR 50 MILLION YEARS Examples of cephalopods: squids, octopuses, nautilus, etc…

Mollusks in DANGER There are many species of mollusks that are endangered, right here in the US! (not to mention around the world). The most commonly stated cause for their endangered condition is “Habitat destruction and degraded water quality due to impoundments, channelization, agricultural practices, inceasing barge traffic and siltation, and reduction of water flow.” (

Video on Endangered Mollusks in Kentucky

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