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

Water exits from funnel or siphon

Direction of water out of 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

• 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

Long & retractable

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=H8oQBYw6xxchttp://www.youtube.com/watch?v=ygh1-ul6E94

• Vampire squid from hellhttp://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 World Cup champions!