Transcript Phylum Mollusca, Class Cephalopods

Phylum Mollusca, Class Cephalopods
• Cephalopods (Class Cepahlopoda) are a group
of molluscs that include squid, nautilus,
cuttlefish and octopus
• They are the most highly evolved of all
molluscs; nearly all are agile swimmers with a
complex nervous system
• Cephalopods have a reduction in or loss
altogether of the shell
Phylum Mollusca, Class Cephalopods
• Cephalopods (which means “head-footed”)
have heads surrounded by a foot modified
into arms and tentacles, usually equipped
with suckers that are used to capture prey
Phylum Mollusca, Class Cephalopoda
• Largest of all Molluscs
• All have a radula, beak-like structure
• Cephalopods have large eyes, with acute
vision, extremely sensitive to slight details and
impressions
Phylum Mollusca, Class Cephalopods
• Cephalopods pump water through the siphon,
or funnel into their mantle cavity
• By forcing water out of the mantle cavity
through the siphon, cephalopods swim by
means of “jet propulsion”
• By changing the direction of the siphon,
cephalopods can move backward or forward,
or can remain motionless in one place
Jet Propulsion
Water enters
mantle cavity
Direction of water out of siphon
Water exits from
funnel or siphon
Direction of cephalopod motion
Octopus: Order Octopoda
• One of the most iconic cephalopods is the
octopus
• Octopuses have 8 long arms (“octo” means 8)
and no shell
• Common bottom dwellers, they are efficient
hunters
– Bite their prey (mostly shellfish)
with a pair of beak-like jaws
– Ink sac emits a dark cloud of fluid
to deter predators
Squids: Order Teuthoidea
• Squids are better adapted for swimming than
octopuses
Long & retractable
• Squids have two triangular fins
modified for swimming
• Elongated body
• Squids have eight arms &
2 tentacles, all with suckers
which circle the mouth
http://cas.bellarmine.edu/tietjen/images/Image32.gif
Squids: Order Teuthoidea
• Suckers only at broadened tips on tenacle
• The shell is reduced to a stiff pen embedded
in the upper surface of the mantle
Cuttlefish: Order Sepiida
• Cuttlefish are among the most intelligent
invertebrates
• Cuttlefish have a calcified internal shell called
a cuttlebone, which aids in buoyancy
– Chambered, gas-filled
• Called “chameleons of
the sea” for their
astonishing ability to
change skin color at will
Chromatophores
• Cephalopods control their skin pattern and
color by way of chromatophores
• Chromatophores are pigment-containing and
light-reflective cells used for camouflage
• Inside the chromatophore, pigment granules
are enclosed in an elastic sac
– To change color, the sac is distorted by way of
muscular contraction
Nautilus: Order Nautilida
• Nautilus are called “living fossils”; only 6
species remain of an extinct superfamily
• Survived relatively unchanged for millions of
years
• Gas-filled chambers aid in buoyancy
• Paper nautiluses
are actually pelagic
octopus; named for
the paper-thin
eggcase in females
You will never be as cool as a cephalopod
• Mimic octopus
http://www.youtube.com/watch?v=H8oQBYw6xxc
http://www.youtube.com/watch?v=ygh1-ul6E94
• Vampire squid from hell
http://www.youtube.com/watch?v=S3CJIKKSUpg
www.islandream.com/sangalakigallery7.htm
http://www.itsnature.org/sea/other/colossal-squid/
www.flickr.com/photos/maxcdc/3615629745/
…or as smart???
• Octopuses and cuttlefishes have a remarkable
capacity for learning
• Giant nerve fibers rapidly conduct impulses
allowing cephalopods to capture prey or escape
at amazing speeds
• Most cephalopods display color changes
correlated with particular behaviors and moods
• Octopus are known to use tools, and predict
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