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Journal 1:
• What characteristics do all of these animals
have in common?
PHYLUM MOLLUSCA
I. General Information:
1. Soft bodies usually protected by shell.
2. True coelom
I. General Information
3. Usually have 3 body
regions:
a. Head/foot- locomotion &
retraction of body into
shell.
b. Mantle- thin skin layer
covering visceral mass;
secretes shell.
c. Visceral mass- organs for
digestion, excretion,
circulation, reproduction
II. Classification
1. Kingdom Animalia
2. Phylum Mollusca
3a. Class Gastropoda- snails,
slugs
3b. Class Bivalvia- clams,
oysters, mussels
3c. Class Cephalopoda- squid,
octopus
IIIa. Class Gastropoda
1. Snails, slugs
2. Marine, freshwater,
terrestrial
3. Largest & most varied class
4. Some have shell- univalves (one shell)
a. Apex- center spiral, oldest part of shell
b. Operculum- “door” that closes shell to
prevent dehydration.
Shell
Apex
Eyespots
Pneumostome
Tentacle
Operculum
Mouth
Foot
Head/anterior
A. Locomotion
1. Wave-like contractions of muscular foot.
2. Lay down layer of mucus (terrestrial)
B. Digestion/Feeding
1. Have radula- tongue-like organ with tooth-like
structures for scraping food.
2. Mostly herbivores (algae); some predators
(cone snail- highly venomous)
3. Mouth, pharynx, esophagus, stomach, intestine,
anus.
4. Salivary & digestive glands help breakdown food
C. Respiratory System
1. Gills- aquatic
2. lungs/diffusion- terrestrial
3. Pneumostome- opening to allow oxygen to enter
body.
D. Circulatory System
1. Open circulatory systemblood leaves short vessels
and bathes tissues directly
in blood.
2. Pulmonary vein- conducts
oxygen from gills to heart
via blood.
3. Heart- pumps blood rich in
oxygen to rest of body
thru aorta.
4. Aorta- dumps blood into
spaces around organs
E. Excretory System
1. Nephridium- removes excess liquid waste,
sends to mantle cavity where released to
outside.
2. Aquatic- release liquid ammonia waste
3. Terrestrial- release uric acid in crystal form to
prevent water loss.
F. Nervous/Sensory System
1. Six ganglia throughout body.
2. Sensory structures located at
anterior end- most sensitive
area-retreats into shell first.
a. Anterior tentacle- at front of
head
b. Posterior tentacle- behind
anterior antennae; have eyes
that detect light
c. Osphradia- chemoreceptors that
detect food and predators.
G. Reproductive System
1. Most are monoecious.
2. Can be protandric- testes
develop first & after they
degenerate, ovaries
mature.
3. Eggs are fertilized
internally & layed as
sticky mass.
4. Some marine gastropods
are dioecious.
H. Economic/Environmental Significance
1. Source of food (escargot) & part of food chain
2. Slugs destroy gardens/crops
3. Hosts for parasites of man (flukes)
4. Shells can be used as a source of jewelry
5. Venom can be used in medicine
CFA: SZ3: Students will compare form and
function relationships within animal
groups..
1. What is the purpose of the radula in a
gastropod?
2. Which structure aids in locomotion?
3. What is the opening that allows oxygen to
enter the body?
4. What type of circulatory system to
gastropods have? What does this mean?
5. What does it mean to be protandric?
JOURNAL 2:
• What are all the different ways gastropods
can be used in the environment and for
humans?
IIIb. Class Bivalvia
1. Clams, oysters, mussels, scallops.
2. All marine or freshwater
3. Second largest class
4. All have 2 shells
A. Locomotion
1. Clams/mussels- muscular
foot for burrowing
2. Oysters- adults are sessile
3. Scallops- “clap” their
shell for jet propulsion
B. Shell Features
Prismatic
1. Shell structure
a. Periostracum- thin outer
layer of protein
b. Prismatic layer- thick
middle layer of calcium
carbonate
c. Nacreous layer- inner
layer; secretes nacre which
forms pearls in some.
Nacreous
Periostracum
2. Umbo- swollen area near
anterior, dorsal end of
clam; oldest part of shell.
3. Hinge ligament- holds
two shells together
4. Growth lines- wider lines
indicate more
growth/better feeding
season.
5. Anterior and Posterior
adductor muscles- very
strong muscles for
opening or closing shell.
C. Digestion/Feeding
1. Filter feeders- algae,
larvae, small particles
2. Food/water enter
incurrent siphon.
3. Food swept into mouth by
2 pairs of palps
4. Esophagus, stomach,
intestine, anus
5. feces/excess water leave
thru excurrent siphon.
D. Respiration
1. Oxygenated water enters
incurrent siphon.
2. Gills have tubes where
water & blood are close
together. Gases exchange
by diffusion across the
membrane.
3. Deoxygenated water
leaves thru excurrent
siphon.
E. Circulation
1. Open
2. Heart and short
vessels similar to
gastropods.
F. Excretion
1. Nephridium
G. Nervous/Sensory System
1. Ganglia concentrated in foot,
esophagus, adductor muscle
and mantle.
2. Some have eyes for sensing
light around shell rim.
3. Osphradia- chemoreceptors
H. Reproduction
1. Most are dioeciousexternal fertilization
2. Sperm leave thru
excurrent siphon
3. Sperm brought in thru
incurrent siphon of
female.
4. Clams release
trochophore larvae which
develop into adults.
5. Mussels release glochidia which look like
miniature adults.
• These are usually parasitic on fish.
• Attach to fish gills & feed on blood.
• When adult organs form, they drop off & take
on filter feeding life style.
I. Economic/Environmental Significance
1. Source of food/part of food chain
2. Filter/clean water of harmful pollutants (red
tide algae)- can cause sickness eaten.
3. Form pearls/jewelry
4. Mother of pearl buttons made from
shells
CFA: SZ3,4,5: Answer the
following questions (bivalves).
1. What is the function of the palps in a
bivalve?
2. What comes into the incurrent siphon?
What exits through the excurrent siphon?
3. How do bivalves reproduce?
4. How are bivalves useful for humans and
the environment?
5. Describe the layers of a shell.
JOURNAL 3:
• Compare & contrast bivalves &
gastropods. Use a Venn Diagram and
several similarities & differences.
IIIc. Class Cephalopoda
1. Squid, octopus, nautilus, cuttlefish
2. All marine
3. Most complex mollusk
4. No external shell, have internal support
a. Squid- have internal chitinous structure
called pen
b. Cuttlefish- have cuttlebone. Can be
used as calcium supplement for birds.
c. Chambered nautilus-
has true shell
d. Octopus- has no shell
Anterior
Dorsal
Ventral
Posterior
Dorsal
Ventral
Anterior View
A. Fin
B. Mantle
C. Body tube
D. Articular ridge
E. Eye
F. Arm
G. Tentacle
H. Buccal cavity
A. Locomotion
1. All cephalopods can
move by jet propulsionforcefully expelling water from siphons on
head.
2. Octopus crawl with arms.
3. Squid & cuttlefish have posterior fins for
steering/movement.
B. Digestion/Feeding
1. Have arms with suction cups to capture/hold prey.
2. Sharp beak for tearing into prey.
3. Radula for drilling holes in shells.
4. Use extracellular digestion- secrete enzymes that breaks
down food before enters mouth.
5. mouth, esophagus, stomach (cecum = digestive gland),
intestine, anus, siphon
6. Most nocturnal- eat
Radula
crustaceans, fish,
other mollusks, etc.
Beak
Holes created by octopus radula.
“b” indicates where octopus gave up and used
beak to break into shell.
C. Respiratory System
1. Gills in mantle cavity
D. Circulatory System
1. Closed- blood enclosed in
blood vessels.
2. Have hemocyanin- copper
rich blood (blue)
E. Excretory system
1. Nephridia
F. Nervous/Sensory System
1. Large brains- good memory, can work thru
problems.
2. Complex eye- very similar to human eye. Can
form images and distinguish color
3. Camouflage
a. Chromatophores- pigments cells in skin which allow
color change. Can also use to communicate with other
cephalopods (mating, aggression, fear, etc)
b. Suckers on arms are very sensitive. Can change texture
of skin to match rocks.
4. Ink gland
• ejects ink cloud when disturbed to make quick
getaway.
• tyrosinase- also released to irritate predators eyes
and paralyze sense of smell
G. Reproduction
1. Dioecious
2. Male testes package sperm in a
case called a spermatophore.
3. He uses his enlarged tentaclehectocotylus- to transfer
spermatophore to female’s mantle
cavity.
4. Female lays eggs which pick up
sperm on the way out.
5. Only females have nidamental
gland that secretes outer shell of
egg.
5. Eggs are deposited in string-like masses in octopus
den.
6. Octopus brood young until they hatch. Keeping
clean of debris.
7. Young never cared for after hatching.
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
N.
Cecum
Fin
Testis
Vena Cava
Branchial heart
Gill
Ink sac
Funnel
Tentacle
Arms
Eye
Intestine
Penis
mantle
H. Economic/Environmental Significance
1. Food source- calamari, octopus
2. Bait for commercial fishermen
3. Can be pests in oyster beds- eating up all
profit!
4. Cephalotoxin may be used for medicine/research
•The Giant Squid
•50 feet long & weigh almost 1 ton
•Eats fish & other squid and has been known to
eat sperm whale calves