Transcript Phylum MolluscaADVx

 Soft-bodied
animals covered by a mantle
 Most secrete a shell to protect the soft body
 Coelomates in addition to a mantle cavity
 Head-foot
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Mouth and other sensory organs
locomotion
 Visceral
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Mass
Contains heart, digestive organs, excretory
organs, and reproductive
 Gastropod
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(univalve)
Largest most diverse
Only class with terrestrial members
90,000+ species
1 or no shell
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Twisting of shell lowers center of gravity
Torsion –twisting 180 degrees brings mantle cavity
forward allows snail to bring head in for defense
 In some gastropods, an operculum seals off the shell
Open circulatory system
 Blood –like fluid called hemolymph
 Small to no blood vessels, fluid filled space called
hemocoel
Nudibranch
( naked gill )
“sea slugs”
-Shed their shell in lieu of toxic
defenses
- Acquire many of these toxins as a
result of diet
about 3,000 species
Live only about 1 year and
because there is no shell,
leave very little evidence
National Geographic Magazine - NGM.com
 Bivalvia
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Two shells joined by hinge
Adductor muscles hold shell together
Incurrent and excurrent siphon for filter feeding
Burrow under sand; attach to substrate
No head
 Octopus,
Squid
 No
shell
 Compensation:
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Internal cartilaginous support
Fast locomotion – jet propulsion
Image forming eyes
Closed circulatory system (3 hearts)
Ink decoys, camoflauge
Blue ringed octopus
size of a golfball up
to 8in, no known
antidote, loss of
senses, then
unable to breathe