Mollusks
Phylum Mollusca
Bottled specimens
Kingdom: Animalia
Phylum: Mollusca
Class :
Phylum Mollusca
• Snails, clams, squid, octopus, and
• nudibranchs (sea slugs).
• Soft body, which is protected by a calcium
carbonate shell in gastropods and bivalves,
internal “pen” in squid.
• Octopus, are all soft bodied.
• Body covered by mantle which produces
• shell.
• Bilateral symmetry
• Muscular foot
• Gills for O2 absorption
Kingdom: Animalia
Phylum: Mollusca
Class : Gastropods
Class
• Gastropods: “stomach-foot”
Single shell or no shell - can retract body and
cover with operculum.
Snails, limpets, abalone, cone shells,
nudibranchs (sea slugs) which has no shell.
Sea hare has small shell surrounded by tissue.
Many are herbivores with rasping radula
Some carnivorous, drill hole in clam with
radula. Cone shells have toxin in radula,
harpooning small fish; this toxin may make a
good painkiller.
Reproduction:
Many hermaphroditic / fertilization internal /
development external, some produce egg
cases
Kingdom: Animalia
Phylum: Mollusca
Class : Bivalvia
• Bivalves : two shells
Clams, mussels, and oysters
Their bodies are compressed between two
shells.
They are filter feeders, drawing water in through their siphon.
Two Adductor muscles close hinged shells.
Scallops have one big muscle.
Mantle contains glands that secrete CaCO3 shells. Oysters
secrete cement for attachment also covers sand grain to
make pearl. Mussels attach by byssal thread.
Each line on clamshell represents about one
year of growth. Wide bands may represent favorable
growing conditions.
Giant clams grow 60 years and can weigh
500 kg or 1000 lbs.
Movement:
Scallops open/close to make current “swim”. Clams dig
with muscular foot; some can
burrow through wood.
Reproduction:
Separate sexes release eggs and sperm, external
fertilization and development.