Transcript visceral mass, modified foot, & mantle

• Unsegmented soft body
• Mollusks have 3 main parts
-visceral mass, modified foot, & mantle
• Mollusks have a visceral mass (contains the
organs)
• Mollusks have a Modified Foot
– Muscular foot and/or tentacles
• Have a mantle (fold that wraps around visceral
mass & secretes the shell)
• Most have shell (internal or external)
– Or remnants of a shell
• Pen in squid
• Body Cavity- true coelom
• Symmetry- bilateral
• Organ systems-have organs for circulation, respiration,
digestion, excretion, & nervous system
• Respiration- most gills (some snails
have simple lung)
• Circulation- 3 chambered heart- most
have open circulatory system (but squids
& octopuses have closed circ. system)
• Digestion- one way digestive system:
separate mouth and anus
• Reproduction- most are separate sexes and
reproduce sexually by doing external
fertilization (except for snails which are
hermaphrodites)
• Nervous- brain, eyes, and nerves
• Excretion- nephridia remove wastes
Tentacles/
modified foot
head
Mantle
cavity
Mantle
foot
Shell
Classes of Mollusks
There are 7 classes of mollusks but this course will look at the 3 main classes
• Class Cephalopoda –
octopus and squid
• Class Gastropoda –
slugs and snails
• Class Bivalvia – clams,
mussels, scallops
.
Class Gastropoda
• Types- snails, conches, limpets
free-living; marine, terrestrial, fresh water
• noticeable head
• single shell, often spiral
• muscular foot secretes mucus
to form a slimy path to glide
along
• Feeding-most herbivores
that scrape algae off rocks
with radula
• Mantle- secretes shell
Snail Anatomy
Class Bivalvia
• Types- clams, scallops, oysters
• marine and freshwater
• gill used for gas exchange
• all are sessile, filter feeders and filter food
from the water
• all have two part shells
(bivalves)
• Muscular foot- used to
dig into sand
Class Cephalopoda
•Types- octopus, squid,
cuttlefish
• Exclusively marine
• Shell- “pen”- internal
remnant of a shell
• Use fins and siphon to
move (jet propulsion)
• Modified foot= tentacles
• Fast swimming predators
-use tentacles to catch prey
• Use a beak-like jaw (radula)
to eat prey
• Have a special camera like
eye
Ex- Giant Squid
Squid External Anatomy
Fins
Mantle
Siphon
Squid Internal Anatomy