Mollusks
Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Class Bivalvia
Class Cephlapoda
Mollusks
50,000 species
 10 classes
 Includes:

◦
◦
◦
◦
◦
◦
◦
Squid
Octopus
Clams
Conches
Snails
Sea slugs
Oysters
Basic Anatomical Structures:
a) Mantle – muscular bag that surrounds
the gills and most organs and is used to
circulate water
1. some use it to circulate water or jet
propulsion
2. secretes calcium carbonate shell
Basic Anatomical Structures:
b) Foot – muscular structure used for
movement
1. In snails & slugs it’s used to crawl
2. In bivalves it’s used to dig
3. In squids, it takes the form of
tentacles
Basic Anatomical Structures:
c) Radula – a tongue
like structure with
scraping teeth
Class Gastropoda
Includes snails, slugs,
whelks, & abalone
Defining Characteristics:
- Radula
- Some have a shell
- Sensitive Tentacles
- Shell-less members
can produce toxins or
store eaten
nematocysts
Snails
Sea Slugs
Whelks
Abalone
Class Bivalvia:
Includes clams, oysters,
mussels, scallops
Defining characteristics:
- Two hinged shells
- No head, but sensory
organs on shells edge
- Two siphons extend
out of the shell
- Mantle pumps water
Clam
Oyster
Mussel
Scallop
Clam
Oyster
Mussel
Scallop
Pearl Making Abilities
When ever sand or an irritant gets inside a shell
of an oyster, it coats it in a substance called
nacre, creating a pearl
Pearl farmers put seeds inside oysters to create
pearls
Class Cephalopoda
Includes squid, octopus,
nautilus, cuttlefish
Defining Characteristics:
- Little to no shell, ranging
from gastropod like shell
(nautilus) to internal leaf
like shell (cuttlefish) to
thin internal bar called a
pen (squid) to nothing
(octopus)
Class Cephalopoda
Defining Characteristics:
- Specialized foot called a siphon for jet propulsion
- Ink sac
- Chromatophores – cells that can change color
- Complex nervous systems consisting of large eyes
and critical thinking abilities
Octopus
8 arms
 Beak like jaws
 No shell
 Bottom dwellers

Squid
Better adapted for
swimming due to
elongated body and two
fins formed by the mantle
 Ten arms, two of which
are longer are called
tentacles
 A reduced shell called the
pen can be found
embedded in the upper
surface

Cuttlefish
Resemble squids
 Eight arms and two
tentacles
 Flattened with a fin
along the sides
 Internal Shell

Nautilus
Smooth exterior shell
 Contains several gas
filled chambers that
aid in buoyancy
 Has 60-90 arms to
catch prey
