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Sea Slug
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Mollusk Terms
LATIN LIVES
Phora = Bearing
Mono = One
Placo = Plate
Cephalo = Head
Scapho = Sword
Pelecy = Hatchet
Poda = Foot
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Phylum Mollusca Classes
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Click on any Scientific Name to go to that Class
Aplacophora - mollusks without shells
Pelecypoda ( Bivalve) - clams, oysters, mussels, second
largest species.
Cephalopoda – squid, octopus, chambered nautilus
Gastropoda ( Univalve) – snails, slugs, abalones, whelks,
periwinkles, giant conch, most species
Monoplacophora - mollusks with one shell, ancient
Polyplacophora ( Amphineura) – chiton, eight plates,
intertidal
Scaphopoda - a tubular shell - tusk shells
General information
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Interesting Facts
Start Over
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Invertebrates with
Soft Bodies
“Mollusk”
octopus
They
have existed for 600
million years.
Some are very primitive and
some are quite intelligent
creatures.
They are used commercially
in many ways.
squid
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snail
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Mollusk ~ Snail
Second largest
group in the animal
kingdom
There are more
than 150,000 living
species of the
mollusk.
Half of the species
are marine.
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MOLLUSK ANATOMY
Mollusks vary greatly in the development of each of the
three body sections.
Three main body sections
1.
Head = Eyes, Mouth ( Radula –rasping sucking
tongue) and Tentacles
2.
Visceral Mass = Mantle which secretes the shell, and
the gills, intestines, kidneys, heart.
3.
Foot = large muscular organ to move the body.
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Mollusk Anatomy
Visceral Mass
Shell Coelo
m
Anus
Mantle Cavity
Mantle
Hear Gonad
Nephridiumt
Stomach
Intestin
Gill
e
Nerve Cords
Esophagus
Mouth
Foot
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Mollusk reproduction
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Most mollusks have separate females and males;
gonads are in the visceral mass ~ Sperm or eggs are
produced by meiosis.
Snails are hermaphrodites bearing both female and
male gonads in same individuals.
Sea Slug
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Monoplacophorans
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This is the deep- sea dwelling class that was
the ancestor of all other mollusks.
These animals were thought to be extinct
until 1952
At present, only a few living species are
known to exist.
There are many fossils .
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Monoplacophorans
Nepolina
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Monoplacophorans
Fossil Specimens
Cyrtolites
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Archinacella
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Aplacophorans
These
organisms lack
shells and are wormlike in body form.
They have calcareous
scales or spicules in
their integument.
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Aplacophorans
Soleonogasters which also live on the bottom feed on
cnidarians (Jellyfish – Corals).
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Whelk
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Mollusks Gastropoda (Univalve)
Class
Gastropodameaning stomach foot
Univalve
= one valve or
one shell
Conch
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Mollusks - Gastropods
snails, slugs, abalones, whelks, periwinkles, giant conch
– giant conch – 1
foot length
Urosalprix – “oyster drill”
bores hole in oyster and
digests through the hole.
Largest
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Mollusks - Gastropods
Snails, nudibranchs, cowries, whelks
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Sea Slugs
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Nudibranchs with
symbiotic algae
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Glaucus atlanticus
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Abalone
The Abalone shell is used to make jewelry
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Abalone
Abalone is served in fine restaurants
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Periwinkle
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Periwinkle
Periwinkles
feed on algae and
seaweed.
They are found at the water's
edge on Mash grasses.
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They
move up and down the
grasses in synch with the tides.
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Snails As Bird food
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Snails provide an immense amount of food for
waterfowl in the wetlands.
Mallard - 16%
Pintail - 15%
Blue winged Teal - 38%
Northern Shoveler - 40%
Gadwall - 4%
The endangered
Whooping Crane – 60%
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Whooping Crane
eats snails
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Oyster Shell
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Phylum Mollusca
Class Bivalvia ( PELECYPODA)
Class consist of;
clams, oysters, scallops, mussels
mussels
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What are the shells of mollusks
made of?
Calcareous
material that
resembles
limestone
Oyster Shells
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Scallop
Eyes
Gills (Cilia)
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Clam
Gills with Cilia
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What do clams use for digging
into the sand?
A muscular, hatchet-shaped foot extends from
between the shells and is used for digging.
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Octopus
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Cephalopoda
Class
Cephalopoda are
among the most active,
interesting and intelligent of
the Mollusk.
Cephalopoda means headfoot. Their head is attached
to the foot which become
tentacles
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octop
us
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Class Cephalopoda
octopu
s
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Shell reduced & internalized in squid ( beak)
No shell in octopus
Largest invertebrates
Possess eyes and tentacles
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Mollusks - Cephalopods
All
are carnivorous
octopus
Siphon
allows jet
propulsion in squid
Defenses
include ink
(squid, octopus) and
change in coloration of
octopus
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Mollusks - Cephalopods
Squid, chambered nautilus, cuttlefish, octopus
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Squid
Shell reduced to pen made of chitin
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Cuttlefish
CuttleFish
Cuttlefishes have Carbonate shells
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cephalopods
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The only
cephalopods with a
shell are a few
species of
nautiluses
Nautilus means
shell with
chambers.
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Nautilus
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Chiton
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Class Polyplacophora
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Habitat: Chitons inhabit the intertidal and
subtidal regions.
They live under or on rocks with a very tight
grip to protect them from waves.
Each one consists of Eight plates
Diet: Encrusting plants and animals
Reproduction: Chitons are dioecious, meaning
there are female chitons and male chitons.
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Chiton
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Gumboot Chiton
It
is the largest species of chiton in the world,
It can grow up to 30 cm in length
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Scaphopoda
The
Scaphopoda are known as the
"tusk shells" because their shells are
conical.
The
scientific name Scaphopoda
means "shovel foot", which refers to
the "head" of the animal. It lacks eyes
and is used for burrowing into marine
mud and sediments.
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Scaphopoda
The
most distinctive feature of scaphopods is that the
tubular shell is open at both ends,
Not just one end as in most molluscs.
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Life is Tough
Scaphopods
live their
adult lives buried in sand
or mud, with their headend pointed downwards.
Only the narrow
posterior end of the shell
sticks up into the seawater
for water exchange and
waste expulsion.
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Rapa Whelk
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Introduced Species
Rapa Whelk
Came
from the Sea of Japan
The Rapa Whelk is destroying
the Mid-Atlantic natural
Whelk habitat
No predators
Reproduce rapidly
VIMS has a bounty for
catching them
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The role of the Mollusk
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Can be a check on
pollution levels,
since some are filterfeeding bivalves
Pouch Snails
provides a sign for
what the water
quality is; (the
dominance of pouch
snails signifies poor
water quality)
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Mollusk provide 16% of
the Mallard Ducks Diet
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Mollusks ~ Reproduction
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Some hermaphroditic
mollusks, such as
certain oysters switch
from one sex to the
other.
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Sometimes
producing eggs, and
sometimes sperm
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Mollusks
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Those without shells;
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May spend daylight
hours under rocks
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Some sea hares have a
special “ink” they
squirt.
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Sea Hare
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Mollusks ~ Make Pearls
Oyster with Pearl
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Mollusks Facts
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Snails and other mollusks never seem to develop cancer;
Sea Slug
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Mollusks
There are some negative relationships with humans
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Land slugs and snails are plant eaters that do
damage to crops
Shipworms will damage wood ships- “termites
of the sea”
Shipworms
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