Download Cephalopds(head feet) - BIOL265MarineBiology

Phylum Mollusca
Phylum Mollusca
• Bilateral symmetry
• Body Cavity - Coelomate
• Body has three distinct regions
– Visceral mass - central section, which contains the
body's organs
– Mantle - Means “cloak” in Greek. Wraps around the
visceral mass, secretes shell. Mantle cavity -space
between mantle & visceral mass.
– Foot - Ventral, muscular and prominent.
• Functions:
– Locomotion - Bivalvia use to dig into sand
– Securing food - modified into a tentacle in Cephalopods
Digestive System
• Radula - rasping organ in Gastropods, Beak in
Cephalopods
All mollusks except Bivalvia have this
structure.
• Used to scrape algae off rocks (Gastropoda)
or as a weapon to puncture holes in prey
(Cephalopoda)
• Has mouth, esophagus, stomach, intestine
and anus.
• Digestive gland secretes enzymes into the
gut.
Excretory System
• Nitrogenous wastes dumped into
coelom. Cilia in nephridium cause fluid
(wastes and nutrients) to move through
nephridia.
• Nutrients are reabsorbed; wastes empty
into the mantle, then removed.
Circulatory System
• Open system for all except
Cephalopoda.
• Dorsal aorta - Coelom - restricted to the
region around the Dorsal Aorta.
Respiratory System
• Gills located in their mantle cavity
• Cilia beat continuously causing a steady
stream of water to pass over the gills.
Gills also trap food
Nervous System
• Ring of nervous tissue around
esophagus
• Two sets of ventral nerve fibers
• Nerve fibers maybe quite large - squid
• Photoreceptors, Chemoreceptors and
tactile receptors
Reproductive System
• Male and female
• External fertilization
Major Classes
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Class Gastropoda
Class Bivalvia
Class Cephalopoda
Class Polyplacophora
Class Scaphopoda
Monoplacophora - Primitive
Class Gastropoda - Snails and
slugs
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Examples: Nudibranch - Sea slugs
Mantle secretes hard protective shell.
Some don't have shell.
All terrestrial mollusks are in this class,
but most members are marine.
• Terrestrial mollusks don't have gills.
Class Gastropoda - Snails and
slugs
• Uses Radula to scrape algae for food
• Foot adapted for locomotion. It forms a
slimy path then ungulates foot (wave
like motion)
• Eyes are located on a pair of stalk like
tentacles on the head
Class Bivalvia - Clams, oysters
and scallops
• Examples - Oysters, Scallops, Clams,
• Name means: bi - "two", valva - "part of a door"
• Edge of Mantle secretes a two part hinged shell.
Composed of Calcium Carbonate. Shell shows
growth lines.
• No distinct head region, but have a central
ganglia above foot
• Most are Sedendary/Infaunal, exception scallops
and shipworms. Most are Filter feeders
Class Bivalvia
• Nervous System- touch and photoreceptors
• Muscular System
• Adductor muscles connect the two valves
together.
• Muscular foot used to dig into the sand and
locomotion
• Nutrition - Filter feeders.
• Use a hollow tube called a siphon to pull in
water. Water is then drawn over the gills then
out the excurrent siphon.
Class Bivalvia
• Reproduction
• Sexual, Most species have separate sexes,
few hermaphrodites. Shed sperm and eggs
into water. Fertilization is external.
• Zygote develops into a free swimming
trochophore larva.
• Teredo (Shipworm) - feeds on cellulose that it
ingests
The Atlantic Shipworm (Teredo navalis), introduced in 1913,
resulted in $3.1 billion (in today's dollars) in damage to wooden
structures on the Bay between 1919 and 1921.
Class Polyplacophora chitons
• Shell is embedded in mantle
• Mantle cavity has two lateral grooves on
each side of body where gills are
located.
• Use Radula to scrap algae
• Reproduce externally, Separate sexes
Cephalopods(head feet)
Invertebrate
Video Clip
Cephalopods History
• appeared some time in the late Cambrian several
million years before the first primitive fish began
swimming in the ocean
• Scientists believe that the ancestors of modern
cephalopods (Subclass Coleoidea: octopus, squid,
and cuttlefish) diverged from the primitive externally
shelled Nautiloidea (Nautilus) very early - perhaps in
the Ordovician, some 438 million years ago.
Cephalopod Hist. cont
• Cephalopods were once one of the
dominant life forms in the world's
oceans
• Today there are only 650 or so living
species of cephalopods (compare that
with 30,000 living species of bony fish).
However, in terms of productivity, some
scientists believe that cephalopods are
still giving fish a run for their money
Cuttle fish Sepioloidea
lineolata
Squid Taningia danae
Octopus Hapalochlaena
lunulata
Cephalopods
• Fast swimming predatory animals
• Extremely intelligent
• Cephalopods foot is divided into
tentacles
– squid=10 tentacle
– octopus=8 tentacle
– cuttle fish=6 or more tentacle
Cephalopods distinct
structures
• Cephalopods have large, well developed eyes that
form images
• Tentacles are covered with suckers for seizing and
holding prey
• Cephalopods have a rasp like structure in their
digestive tract called a radula for breaking down food
• Cephalopods mouth has two strong beaks for tearing
its prey apart.
• Cephalopod is fitted with a funnel like structure that
fills with water and ejects it acting like a jet
propolsion
Cephalopods masters of
deception
• Able to change multi colors
• Can expand and contract pigment cells
in its skin
• Chromatophores(color cells) give the
cephalopod the ability to change.
• Can eject ink when alarmed causing the
enemy to be temporarily blinded. The
ink also inactivates predators chemical
receptors used for detecting prey.
Cephalopods Diet
• Feed on crabs, shrimp, fish, and other
cephalopods
Cephalopods Habitat
• Intertidal to abyss
• Polar to tropics
• In other words they are found
everywhere
The Infamous Giant Squid
Architeuthis
Giant Squid – Video
Sperm Whale Clip
• Giant squid get up to 60 feet (20 m) in
length and easily hold the record as the
worlds largest invertebrate
• Despite the size of these beasts no one
has ever seen one alive in its natural
environment or have they???
• Main Diet of the sperm whale
• Giant squid were once mistaken for sea
monsters in sailing days