Transcript Mollusca_Day_1

Molluscs
Phylum: Mollusca
• Kingdom: Animalia
• Mollusca = “soft
bodied”
• Over 100,000
species in this
phylum
• Examples: snails,
slugs, clams,
oysters, squid,
octopus, nautilus &
cuttlefish, chitons
Characteristics of All Mollusks
• Soft-bodied invertebrate covered
with protective mantle (may or
may not form a hard, calcium
carbonate shell)
• True fully-lined coelom (body
cavity)
• Cephalization – distinct head with
sense organs and brain
• Muscular foot – used for
movement (modified into
tentacles/arms for squid and
octopus)
Characteristics -cont.• Scraping mouth-like
structure called the radula
• Free-swimming larval stage
called trochophore
• Body organs called visceral
mass lie below mantle
• Most have separate sexes
that cross-fertilize eggs
• Bilateral symmetry
Characteristics -cont.• Have circulatory,
respiratory, digestive
(1-way with mouth
and anus), excretory,
nervous &
reproductive systems
• Gills between the
mantle and visceral
mass are used for gas
exchange
4 Classes
• Cephalopoda (squid, octopus,
nautilus, cuttlefish)
• Pelecypoda/Bivalvia (clams, oysters,
mussels, etc)
• Polyplacophora (chitons)
• Gastropoda (snails, slugs,
nudibranchs, conchs, abalone, etc)
Class Cephalopoda
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All marine (~ 650 species)
Well developed head & eyes
Thick mantle covers the body
Use beak-like jaws and radula
to crush or rip prey
• Active and free swimming
predators
• Largest mollusks in size
• Shell may be absent (octopus),
reduced to a stiffening rod
(squid) or coiled (nautilus)
Cephalopoda
• Foot adapted into
arms with suckers
• Closed circulatory
system
• Highly developed
nervous system
• Separate sexes with
internal fertilization
Squid
• Large complex brain
• 8 arms/ 2 longer
tentacles to catch prey
• Uses jet propulsion to
move by forcing water
out their excurrent
siphon
• Can squirt an inky
substance into water to
temporarily blind
predators
Squid
• Chromatophores in
skin help change
squid color for
camouflage
• Have internal shell
called pen
• Female lays eggs in
jellylike material &
protects them until
hatching
Squid
• Largest mollusk is a giant squid
• Can grow up to 40-50ft including tentacles
• Hunted by sperm whales
and suction marks on whales
show they fight
Giant Squid
http://www.youtube.com/watch?v=uLRY1cNxL1
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piglet squid
http://video.nationalgeographic.com/video/news/animals-news/marine-censusgraphics-vin/