Phylum Mollusca

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Phylum Mollusca
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Phylum Mollusca

• Mollusks are soft-bodied animals that usually
  have an internal or external shell.
• Mollusks include
• Snails
• Slugs
• Clams
• Squids
• Octopus

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Mollusca Characteristics

• Soft body
• External or internal shell-
• Muscular foot and visceral mass (covered by
  mantle)
• Radula in most-used to scrape food
• Bilateral symmetry
• No segments
• Coelomates
• Open circulatory system- blood not always in a
  vessel
• Trochophore larvae

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Trochophore larva-paddlelike, bristles
Apical tuft
Stomach
Ciliary band
Mouth
Anus
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Phylum Mollusca Anatomy

• The body plan of most have 4 parts
• mantle, shell, visceral mass, and foot.
• 1.The mantle is a thin layer of tissue that
  covers most of the mollusks body like a cloak.

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Phylum Mollusca Anatomy

• 2. The shell is made by glands in the mantle that
  
• secretes calcium carbonate.
• -- Reduced or lost in slugs
• -- Internal or lost in Cephalopods
• 
  (squid/octopus)

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Phylum Mollusca Anatomy

• 3. Visceral mass is just beneath the mantle and
• consists of the internal organs.

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Phylum Mollusca Anatomy

• The muscular foot takes many forms
• flat structures-crawling
• spade-shaped- burrowing
• tentacles-capturing prey.
• clip-giant octopus capturing preyl

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Phylum Mollusca Feeding

• Most Mollusks have a radula a rough,
  tongue-like organ with rows of teeth-like
  structures.
• -scrape algae off surfaces
• - rasp up flesh from prey.

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Body Systems

• Muscular-Skeletal - outer shell, soft body,
  muscular foot for movement.
• Digestion food brought in through a siphon
  system? mouth?digestive gland ?intestine?anus.
• Nervous- A Mollusk has no formal nervous system,
  but has a series of ganglia that conduct
  impulses.
• Circulatory - heart, blood and blood vessels,
  open
• Respiratory- tubes called siphons- bring water in
  and out of their bodies to take in oxygen and
  give off carbon dioxide.
• gills- help with this.
• Reproductive- separate males or female and
  reproduces sexual- with a large gonad.
• Excretion- nephridium that gets rid of wastes?
  anus

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Checkpoint

1. How are mollusks different from other animals we
   have studied?
2. Describe their larval stage.
3. What are the 4 main parts of a mollusk?
4. Which one secretes the shell? What are shells
   made of?
5. How do mollusks respire?
6. What do they use to remove nitrogenous wastes?

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Classes of Mollusks

• There are 8 classes of Mollusks (Covering 5)
• Class Monoplacophora placo-plate
• Class Polyplacophora Chiton
• Class Gastropoda snails, slugs, sea hares
• Class Bivalvia clams, oysters, mussles
• scallops
• Class Cephalopoda octopus, squids, cuttlefish,
• 
  nautilus

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Class Monoplacophora

• Mono one
• Placoplate
• Phora to have or bear
• Mollusks with a single, curved shell
• Marine
• Thought to be extinct until one was found in 1952

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Class Polyplacophora

• Poly many placo plates
• shell is divided into 8 curved plates
• or shells
• Marine
• Have a reduced head and a flattened foot
• Ex. Chiton?

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Polyplacophora

• When disturbed, the edges of the mantle
• tightly grip the substrate creating a
  powerful
• vacuum that holds the chiton in place
• Has the ability to roll into a ball when
  dislodged

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Class Bivalvia

• Clams, Oysters, Mussels Scallops
• Live in water, filter feeding
• 2 shells held together by powerful
  muscles(hinges)
• No radula
• Hatchet shaped foot
• (pelecy) for burrowing

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Class Bivalvia

• only Mollusks that do NOT have a radula
• Feed by siphoning and filtering large particles
  from water
• Can survive for short times out of water by
  closing their valves
• Scallops can move around by flapping their
• shells when threatened.

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Class Bivalvia
Oyster Catcher
Willet
Plover

• Starfish, many sea birds (Oyster Catchers,
  willets, plovers, and much more), and walrus feed
  on them
• The largest bivalve is the Giant clam (clip)
• Can weigh more than 450 lbs

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Class Bivalvia Making Pearls

• Oysters filter-feed
• An irritant, such as a grain of sand, becomes
• embedded in the mantle.
• The animal coats the irritant with the same
  material
• used to produce the lining of its shell
  called mother-
• of-pearl.
• The coating makes the irritant less painful.
• It continues to coat the irritant, creating a
  pearl.

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Class BivalviaImportance

• Bivalves are filter feeders
• valuable service by reducing suspended particles
  in their habitats
• If their populations are reduced, their water in
  that area will become turbid (cloudy)
• Turbid water reduces light penetration for
  photosynthesis in sea-grasses and algae
• Without plants, many other populations of
  organisms will also decrease

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Class Bivalvia Eating Bivalves
Mmmmmmm

• Oysters on a half-shell
• Considered an aphrodisiac
• Eaten fried, Steamed, or raw

Mmmmm.
GOOD!
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Class Gastropoda

• Gastropoda means stomach foot
• Includes snails, slugs, sea hares
• Most are single shelled- asymmetrical and
  coiled
• Some are shell-less (slugs sea hares)
• Radula for scraping food

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Class Gastropoda

• They are 2nd only to insects in their number of
• known species
• gardens, woodland, deserts, rivers and lakes
  estuaries, mudflats, the rocky intertidal, the
  sandy subtidal, in the depths of the oceans, and
  many other ecosystems
• queen-conch/strombus-gigas/video-00.html

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Class Gastropoda

• They move using a muscular foot
• Many have 2 or 4 tentacles
• with eyes on the tip
• Most have a coiled shell that
• opens to the right
• The Lightning Whelk is the only
• left handed snail
• Gastropod clip- Oahu tree snail

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Class Gastropoda

• Many have an operculum that is used as a
  trap-door to close the body inside the shell
• Most breath using gills

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Class Gastropoda Importance

• Many animals feed on gastropods
• -- Example Sea otters eat abalone

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Class Gastropoda

• Hermit crabs inhabit empty snail shells.
• When the crab gets too big for the shell, they
• find a larger one.
• Hermit crabs have wars for prized shells.
• http//www.arkive.org/common-hermit-crab/pagurus-b
  ernhardus/video-03.html

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Class Gastropoda

• Suborder Nudibranchia
• - Means Naked gill
• - marine, shell-less gastropods
• - The gills are arranged as feathery
• plumes on their backs
• - Are brightly colored
• Warning many are poisonous
• Camouflage

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Class Cephalopoda
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Class Cephalopoda

• Typically soft-bodied with the head attached to a
  single foot.
• The foot is divided into tentacles or arms.

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Cephalopoda Locomotion

• Most swim by forcefully expelling water from the
  mantle cavity through a ventral
• funnel (Siphon).
• Swim using jet propulsion method.
• Funnel can point forward or backward to control
  direction
• The force of water expulsion determines speed.

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Cephalopoda Feeding

• beaks similar to a birds beak, used for
  crushing and picking apart food.

Beak
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• Masters of disguise!
• -- Color changes are possible due to special
• pigment cells contained within its skin,
  called
• chromatophores.

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Cephalopoda

• Chromatophores small structures filled with
  colored ink which can be expanded and contracted
  to communicate with others or as camouflage
  against the landscape.

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Cephalopoda

• Color changes are used for
• - Camouflage
• - Communication (alarm/courtship)
• - Many are bioluminescent to attract prey
• and mating partners!

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Octopus are Highly Intelligent

• Maze and problem-solving experiments have shown
  that they do have both short- and long-term
  memory.
• Can be trained to distinguish between different
  shapes patterns
• Observed having
• observational skills

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Class Cephalopoda

• Octopus
• - Have 8 arms
• - Arms have sucking disks
• that grab hold prey.
• - Blood is pale blue.
• - The shell is absent!

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Class Cephalopoda

• More
• Octopus
• - When female lays eggs, she stops eating,
  protects her eggs until she dies.

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Class Cephalopoda

• Blue-ringed Octopus
• - The most toxic
• A bite is nearly always fatal to humans.
• Giant Octopus
• Can weigh 600 lbs
• Known to attack ROV and bite into metal

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Class Cephalopoda

• People eat octopus Dead or ALIVE!
• A dish called San Nakti means living octopus
• -- Kind of difficult to get the octopus down
  because the tentacles stick to your mouth and
  throat.
• -- They also have a tendency to walk off your
  plate!

Hungry?
Hungry?
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Cuttlefish Squid

• Have 10 appendages (decapods)
• 8 arms with suckers and 2 long retractile
  tentacles

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Forms of Cephalopoda

• Cuttlefish
• -- Have an internal gas filled bone that
  helps
• with buoyancy called the cuttlebone.
• -- Well, it is not for sharpening the beak.
  It's amazing how many pet owners think this is
  its purpose. Cuttlebone is provided to birds as a
  source of calcium and other necessary minerals.
  It is especially important to breeding hens.

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Forms of Cephalopoda

• Squid
• -- Color changes reflect the animals mood.
• -- Messages
• ready to mate, sexual identification,
  alarm,
• ready to hunt, hiding.

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Cephalopoda Squid

• Squid
• Most of the shell has disappeared, leaving only a
  thin, horny strip called a pen which is enclosed
  in the mantle.

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Cephalopoda

• Squid
• Giant Squid are the largest
• invertebrate
• Have the largest eyes in
• the animal kingdom
• Never been seen alive!!!
• Their bodies wash up onto
• beaches
• Sperm whales feed on giant squid

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Forms of Cephalopoda

• Nautilus
• http//www.arkive.org/nautilus/nautilus-pompilius/
  videos.html

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Forms of Cephalopoda

• Nautilus
• -- Sticking out from the shell is the
  nautiluses
• arms and a leathery hood that closes the
• animal into its shell for protection.
• -- This nautilus has more than 90 arms.

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Forms of Cephalopoda

• More Nautilus
• -- only cephalopod encased in a shell.
• -- The nautilus can fill the chambers it doesnt
  occupy with gas or water. If the chambers are
  filled with gas, the animal will float. If the
  chambers are filled with water, the animal will
  sink.

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Forms of Cephalopoda

• More Nautilus
• -- living animal inhabits only the last
• chamber.
• -- As it grows, it moves forward, secreting
• behind it a new septum.
• -- chambers are connected by a cord of
• living tissue called a siphuncle, which
• extends from the visceral mass.

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Nautilus
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Table 1 Classes of the Phylum Mollusk Table 1 Classes of the Phylum Mollusk Table 1 Classes of the Phylum Mollusk Table 1 Classes of the Phylum Mollusk Table 1 Classes of the Phylum Mollusk
Scientific Name Pronunciation Common Name Shells Foot of Species
Polyplacophore chitons 8-plates 650
Monoplacophores 1 ? extinct
Gastropoda GAS-troh-pahdz univalves (snails, slugs) 1 or none stomach foot 90,000
Bivalvia Pelecapoda bivalves 2 hatchet foot 8000
Celphalopoda SEHF-uh-loh-pahdz octopus, squids internal head foot 650

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The End of Mollusca
Polyplacophore (many plates). Amphineura.