B. Circulation - s3.amazonaws.com
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Transcript B. Circulation - s3.amazonaws.com
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