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Phylum: Mollusca
(continued)
• Gastropods:
–Meaning “stomach-footed” - a
head with a flattened foot
–May or may not have a shell
I. Shelled Gastropods
(Snails)
• A. Digestion: One way digestive tract
(in the mouth, out the anus)
• B. Circulation: Have a 1 chambered
heart
• C. Breathing: Breathes by taking water
into its siphon tube, which brings it to
internal gills
D. Movement in snails:
• Moves along surfaces by a muscular foot
• Have 2 sets of tentacles: Anterior
(front) and Posterior (back):
–Front pair are used for a sense of
touch
–Back pair are used for seeing
Types of Snails
1. Mud Snails:
•Are scavengers – eat dead
or dying organisms
•Use a Radula to tear and
shred dead matter
Mud snails on a dime
2. Moon Snails
Feed on live clams
• Secrete a chemical out of the foot to
soften the shell
• Uses a radula to drill a hole in the shell
• The snail inserts its mouth and eats
the clam
3. Cone Snails
• Are predatory snails
• Have toxins which are used to kill
prey
–These toxins are of great interest
to scientists and are being studied
for their benefits to humans
Anatomy of a cone snail
Cone snail’s harpoon-like
radula
• Used to spear
small fish
• Then delivers
poison to its
prey
II. Shell-less Gastropods
1.The Sea Hare
A. Appearance: Have no shells
or the shell is very small
B. Diet: Graze on algae
C. Protection: Some release
dark ink for protection
D. Life cycle: (beginning to end)
is about 1 year
E. Reproduction: Are
Hermaphrodites – Male at the
front end and female at the
back end
Sea Hare reproduction
Are Hermaphrodites
Are Male at the front end and
female at the back end
They can be seen mating in large
chains
They lay up to 80 million eggs in a
group, and resemble spaghetti
California Brown Sea Hare
• The largest
gastropod in
the ocean
• Can grow up
to 2½ feet long
2. Nudibranchs or Sea Slugs
Name means “Naked Gills” (gills
are easily seen on its back)
Are more than 3,000 species
worldwide
Have Rhinophores (-tentacles
on top of the head used for
finding food and a mate)
Rhinphores of a nudibranch:
Nudibranchs (continued)
• Many have finger-like structures
on their back called cerata
• Many are brightly colored, but a
few have subtle colors for
camaflouge
Cerata of a Komodo Dragon
nudibranch:
Dorid Nudibranch
Dorid Nudibranch
Glossodoris Atromarginata
Blue
Nudibranch