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MOLLUSCA
Squids, and slugs, and snails, oh my...
INCLUDES:
Slugs
 Snails
 Squids
 Clams
 Oysters
 Scallops
 Albalones
 Conches
 Periwinkles
 Whelks
 Limpets
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Cowries
 Cones
 Octopi
 Cuttlefish
 Nautili
 Marine animals
 Freshwater living
animals
 Terrestrial animals
 Sessile animals
 Mobile animals
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UM... WHAT DO ALL THESE HAVE IN
COMMON?
All have BILATERAL SYMMETRY
 All are COELOMATES
 All have TUBE-IN-TUBE digestive systems
 All have a MUSCULAR “FOOT” – Used for
mobility and/or grabbing hold of food
 All have a MANTLE – An outside membrane that
protects the mollusk. May secrete a shell.
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CLASSES OF MOLLUSCA
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Gastropods – Snails, Slugs,
Abalones, Conches, Periwinkles,
Whelks, Limpets, Cowries,
Cones
Bivalves – Clams, Oysters,
Mussels, Scallops
Cephalopods – Octopus, Squid,
Cuttlefish, Nautilus
GASTROPODS
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Largest class of Mollusks! Contains 80,000 species!
Use their muscular foot to move around
Feed by using their teethed tongue-like radula to
drill into an dismantle food
Can be herbivores, predators, scavengers, parasites
Marine are usually separate sexes, terrestrial species
are often hermaphrodites
In land species, often use “Love Darts” to get in the
mood!
GASTROPOD SYSTEMS
Nervous system: Ganglia, eyes, and
advanced olfactory (smell) organs
 Circulatory system: Open
circulatory system with a small
heart which pumps around
hemolymph
 Respiratory system: Gills in marine
species, primitive lung in the
mantle of terrestrial species
 Excretory system: Contain
Nephridia, which filter wastes
from the coelom and excrete out the
mantle
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BIVALVES
Have two shells, made of calcium carbonate, held
together by a ligament and controlled by muscles.
 No developed head, do not use a radula.
 Filter feeders! Push water through gills, which
use cilia to sort out food and push it too the
mouth.
 Most have separate sexes (some are
hermaphrodites) and expel sperm/eggs into the
water  external fertilization
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BIVALVE SYSTEMS
Nervous System: Very simple, basically a nerve
net but with a few scattered ganglia, have light
detectors
 Circulatory System: Open, a three chambered
heart pumps hemolymph around the body cavity
 Respiratory System:
Use Gills
 Excretory System:
Use Nephridia
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CEPHALOPODS
Foot has evolved into tentacles which can capture
and hold prey
 Food is then bitten apart with a beak, and torn to
digestible pieces by the radula
 Move about using a “jet ski” like ability to shoot
water out of their siphons
 Some can also expel a dark
fluid when threatened
 Reproduce with separate
sexes, often die afterwards
 Live (grow) fast, die young
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CEPHALOPOD SYSTEMS
Nervous System: Most
intelligent invertebrates!
Large brains and sophisticated
nerve fibers. Very acute vision
and hearing.
 Circulatory System: Closed
circulatory system, with one
heart for the body and two for
the gills
 Respiratory System: Use Gills
 Excretory System: Use Large
Nephridia
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