Download Phylum Mollusk

Phylum Mollusk
Snails, Clams, Squids, etc.
Trochophore Larvae – the stage of organism
after gametes have been fertilized
Why they are Mollusks
Classification of Mollusks
 unsegmented soft
body
 internal or external
shell
 trochophore larva
 mantle – thin, delicate
tissue layer lining
 muscular foot
 visceral mass
Feeding
 herbivores, carnivores, filter feeders, detritus
feeders, parasites
 herbivory and predation (eg. snails, slugs)
radula
 tongue-like structure with hundred of tiny teeth
 Filter-feeders (eg. clams, scallops)
gills (in mantle cavity)
 filter food from water
Octopus eating Crab
Respiration
 Aquatic mollusks
(eg.sea slugs, squid)
Gills in mantle cavity
 Land mollusks (eg.
land snails and slugs)
modified mantle cavity
lined with blood vessels
Internal Transport
 oxygen and nutrients are
transported by blood
 open circulatory system
 no blood vessels, have
sinuses
 for slow moving animals
 closed circulatory system
 blood travel in blood
vessels
 fast moving animals
Excretion
undigested solid waste (feces) through
anus
nitrogen-containing waste removed from
the blood by nephridia
Response
 varies greatly
between classes
 less active mollusks
small ganglia near
mouth
nerve cords
simple sense organs
 active mollusks
well-developed brain
Reproduction
 separate sexes
 external fertilization
 release eggs and sperm
into open water
 Exceptions:
 cephalopods and some
snails– internal
fertilization
 oysters can change sex
Snail Courtship
Mating Snail Sperm Darts
Classes within the Phylum
 7 classes
 Class Gastropods
eg. snails and slugs
 Class Bivalvia
eg. clams, oysters and
scallops
 Class Cephalopods
eg. octopi and squids
Survival Game