Mmmmm…Molluscs!
What mollusks have you eaten?
Who has eaten clams? Clam chowder
“On the half
shell”
Who has eaten squid? Calamari
What has eaten oysters?
Who has eaten snails? Escargot
Characteristics
Soft-bodied invertebrate covered with protective
mantle that may or may not form a hard, calcium
carbonate shell
Second largest animal phylum
Includes: chitons, snails, slugs, clams, oysters,
squid, octopus, and nautilus
Chiton
Slug
Snail
Clams
Oysters
Nautilus
Squid
Octopus
Characteristics
Have a muscular foot for movement which is
modified into tentacles for squid and octopus
Characteristics
Complete one-way digestive tract with a mouth
and anus (unidirectional)
Have a fully lined coelom (eucoelomates)
Characteristics
Cephalization – have a distinct head with sense
organs and brain
Have a scraping mouth-like
structure called the radula
Go through a free-swimming
larval stage called trocophore
Characteristics
Body organs called visceral mass lie below
mantle
Systems they have: circulatory, respiratory,
digestive, excretory, nervous, and reproductive
Bilaterally symmetrical
Characteristics
Most have separate sexes that cross-fertilize
eggs
Gills between mantle and visceral mass are used
for gas exchange
4 Classes of Mollusks
Polyplacophora: chitons
Gastropoda: snails, slugs, nudibranchs,
conches, abalones
Bivalvia (Pelecypoda): clams, oysters, mussels
Cephalopoda: squid, octopus, nautilus
Class Polyplacophora
All marine
Have a shell divided into 8 overlapping plates
Live on rocks along seashore
feeding on algae
Chitons are in this class
Class Gastropoda
Head has a pair of retractable tentacles with
eyes located at the ends
Have a single shell or valve (snails) or none
(slugs)
Known as univalves
VALVE = SHELL
Class Gastropoda: Snails
May be marine, freshwater, or terrestrial
Aquatic snails breathe through gills and use
their radula to scrape algae for food
Terrestrial snails use their mantle cavity as a
modified lung and also saw off leaves
Have an open circulatory system
Class Gastropoda: Snails
Land snails are hermaphrodites but do not
fertilize their own eggs
Aquatic snails have separate sexes
All snails use internal fertilization
Class Gastropoda:
Pteropods
Called “sea
butterflies”
Marine
Have a wing like flap
for swimming
Class Gastropoda: Oyster
Drills
Radula modified to
drill into oyster shells
Feeds on the soft
body inside the shell
Can be devastating
for commercial
shellfishing
Class Gastropoda:
Nudibranch
Marine slug
Lacks shell
Colorful