Transcript Mollusca_Day_3ppt

Class Polyplacophora
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800 species
All marine
Shell divided into 8 over-lapping plates
Have no eyes or tentacles
Ventral muscular foot
Ventral mouth with radula
Mostly found in shallow water, coastal
environments of hard substrate
• Many graze on algae & small animals in
marine intertidal zone (area between high
and low tides)
• Scrapes algae off rocks using radula
• Ex: Chitin
Class Polyplacophora
Class Gastropoda
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Name means "belly-footed"
Also known as Univalves
Moves by muscular foot
Shell opening covered by
operculum, a tissue that acts
like a trap door
1 way digestive track
Breathes through siphon tube
Has gills
Uses antennae to sense
surroundings
Coiled shell on most species
No shell on sea slugs
(nudibranchs)
Operculum
Class Gastropoda
• Radula for grazing on plants (algae) in most, some
are deposit feeders
• Some species are carnivorous and use radula for
prey capture (some will even prey on members of
the same species)
• Impulses in brain reach muscles in foot by way of
motor nerves
• The moon snail is a predator and drills holes into
clams and mussels with its radula
• The cone snail uses a toxin at the end of its
radula to harpoon prey and kill them
Ex: Snails
• Marine, freshwater,
terrestrial
• Open circulatory
• Secrete mucus & use
foot to move
• Land snails
hermaphrodites;
aquatic separate sexes
• Retreat into shell in dry
periods & seals
opening with mucus
• Plant eaters, predators
or parasites
Ex: Slugs
• Live in moist
environments
• Lack a shell
• Dries out quickly
• Secretes thick mucus
to keep skin moist
• Sea slug secrets a
poisonous mucus to
ward off predators
Operculum
Ex: Nudibranch
• Marine slug
• No shell
Nudibranchs
• http://www.youtube.com/watch?v=KzvweoAd
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