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Phylum Mollusca
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Mollusca Vocabulary
Complete a vocab grid. Color on front. Remember to draw &
# squares on back. Some are in text and NOT in the
glossary. BE THOROUGH
1. Trochophore
3. Visceral Mass
5. Mantle Cavity
7. Gastropoda (class)
9. Hemocoel
11. Incurrent Siphon
13. Excurrent Siphon
2. Mantle
4. Ganglion
6. Radula
8. Hemolymph
10. Bivalvia (class)
12. Cephalopoda (class)
14. Hydraulic skeleton
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PREVIEW CARDS
I. Characteristics of phylum Mollusca (pg. 190, 192)
II. Identify examples of the 3 main classes:
Gastropoda, Bivalvia, Cephalopoda
III. Explain the importance of torsion
IV. 3 plausible advantages of torsion
V. Shell and associated structures of bivalves
VI. Sketch of Bivalve shell Fig. 12.9
VII. Bivalve diversity
VIII. Cephalopod shell or lack thereof
IX. Chromatophores in cephalopods
Taxonomy
Kingdom: Animalia
Phylum:
Mollusca
Class:
Gastropoda
Bivalvia
CephalopodA
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Phylum Mollusca
http://www.youtube.com/watch?v=jsxAr_yrJtM
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Mollusks
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50,000 -100,000 living species
35,000 extinct species
Largest = 1000 pounds
80% less than 5 cm
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• Name comes from latin
“molluscus”, meaning soft body
• Most have a shell
• Most marine
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Phylum Mollusca
• Triploblastic
• Symmetry:
Bilateral
• Coelomate
• Protostomes
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Mollusca share 3 common features:
• A muscular foot –
usually for movement
• A visceral mass –
including internal
organs
• A mantle – envelopes
visceral mass and
secretes a shell
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Dorsal mantle covers the
visceral mass.
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Secretes the shell
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Gills (Respiration)
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Complete digestive system
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Paired ventral nerve cords
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Radula
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Coelom - metanephridia
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Body Plan
Pericardial cavity
Metanephridium
Mantle cavity
Gonad
Gills
Radula
Stomach and digestive gland
Foot
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Mollusk General Anatomy
Class Bivalvia
Clams, Oysters, Shipworms, mussels,
Scallops
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Class Bivalvia
• Two shells
• Most are filter
feeders
• No head or
radula
• Burrow
– Sand, wood,
rocks
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Bivalve Anatomy
Giant Clam & Burrowing Clam
Siphon
http://www.youtube.com/watch?v=HrBijKf0
Ywk burrowing clam Pismo clam
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Giant Clam
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Zebra Mussel
• Environmental Pest
• Ballast water of
ships from Europe in
1986
• Attack by secreting
adhesive byssal
threads
– Each other
– Other mussels
– Man made objects
• Pipes, plumbing
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Zebra Mussel
• Live in high densities
• Feed on
phytoplankton
• Reproduce rapidly
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Zebra Mussel
• Attach to native
mussels
• Killed all native
mussels in Lake Erie
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Distribution of Zebra Mussel
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ZEBRA MUSSEL INFESTATION
• http://kxan.com/2014/06/30/new-statewiwderegulations-will-impact-lake-users/
• https://www.kickstarter.com/projects/11693684
54/the-threat-of-zebra-mussels-in-bc-a-shortdocument
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Zebra Mussels
• Major issue in St. Lawerence River and Great
Lakes
• Taking over Midwest waters
• Economic impact: mussels plug up pipes & the
cost to remove them
• Environmental issue: remove crucial feeding
needs for fish in the ecosystem
• HOW TO STOP THE SPREAD:
• 1. clean boat before leaving
• 2. drain all water before leaving
• 3. dry boat thoroughly before going to the
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next lake
Oyster Ecology
http://www.youtube.com/watch?v=HeqtLl4313M&feature=related
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Oysters in NYC
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Used to be oyster capitol of the world
Oysters filter water and sediment
28-48 hours to filter a bucket of water
Oysters act as an anchor for coastline to help
prevent erosion
• Oyster reefs are formed by larvae settling on
top of each other
• Epifauna: organisms that don’t move but grow
on other structures
• Researchers are using ions in sea water paired
with electric charge to speed up shell
secretion mineral ecretion
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Oysters in NYC
http://www.youtube.co
m/watch?v=IFnbnJ8k
GQQ
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Pearl Formation
• Grain of sand or parasite gets stuck in the
soft body of the mollusk
• Oyster secretes a substance called NACRE
(calcium carbonate base) around the foreign
body
• Continues to secrete this (sometimes for
years)
• The oyster’s defense mechanism is nacre
• Eventually a pearl is formed
• Made of millions of microscopic crystals
• Crystals reflect and refract the light to give
the pearl its look
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Oysters – The Ultimate Filters
http://www.youtube.com/watch?v=1ZmyMpHsaQ
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Scallops have fan shaped shell
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Scallop Facts
• Unlike other bivalves like mussels and clams,
most scallops are free-swimming.
http://www.youtube.com/watch?v=_2iXHBuSIJY swimming scallop
• They swim by clapping their shells quickly,
which moves a jet of water past the shell
hinge, propelling the scallop forward
• Scallops have about 60 eyes that line its
mantle. These eyes may be a brilliant blue
color, and allow the scallop to detect light,
dark and motion
http://www.youtube.com/watch?v=u_RfgvIETEY
escaping seastar
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Shipworms not worms at all, but rather a group of
unusual saltwater clams with long, soft, naked bodies
http://www.y
outube.com/
watch?v=A
HcHNoOyv
5I eating
shipworms
they drill passages by means of a pair of very small
shells borne at one end, with which they rasp their way
through. Sometimes called "termites of the sea”
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Class Gastropoda
Snails, Slugs, Conchs, Limpets,
Whelks, Nudibranchs, Abalones
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Class Gastropoda
• Largest Class of
Mollusks about
35,000 species
• One shell (if
present)
• Torsion of body
(visceral mass
twists 180° during
development)
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Torsion
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Gastropod
• Open circulatory
system
• Fluid called
Hemolymph
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Snail
• Terrestrial
• Mantle cavity
functions as lung
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Snail
Pneumostome
Tentacle
(Eye stalks)
Shell
Tentacle
Anus
Foot
Mouth
Genital pore
Add foot and make it #8
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Snails
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CONE SNAIL
http://www.youtube.com/results?
search_query=tueb+snail+eats+fis
h&aq=f
http://www.youtube.com/watch?v=zcBmMP
JrrKk
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Nudibranch
• No shell
• Nudibranchs get their bright colors from the
food they eat.
• Dorsal projections -Gills -Nematocyst
discharge by preying on organisms with nematocyst
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Spanish Dancer Nudibranch
http://www.youtube.com/watch?v=IWmaSk
hsmbY
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http://www.youtube.com/watch?v=WbEmnfY-niU
ABALONE
• Several holes in top of shell
– Excrete waste
• Food for man
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Slug
• No shell
• Garden pests
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Limpet
• Herbivores
• Cling to rocks or other surfaces
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Conch
• Large shell
• Marine
• Many are
predators
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Giant Conch
• http://www.youtube.
com/watch?v=TaaZD
6gX4Rw
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Class Cephalopoda
Squids, Octopuses, Nautiluses,
Cuttlefish
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Class
Cephalopoda
“head
footed”
• Shell in squid and
octopus absent or
vestigial (serves no
obvious purpose)
• Jet propulsion
• Ink sac for defense
• Foot modified into arms
and tentacles
• Marine
• All predators
• Roughly 700 living
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species
Squid
Posterior surface
Right
Ventral
Dorsal
Left
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Squid
Tentacle
Arm
Funnel (siphon)
Collar
Eye
Fin
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Squid
Shell (Pen)
Systemic
heart
Branchial heart
Ctenidium (gills)
Funnel
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Squid Male
Testis
Penis
Hectocotylous arm
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Squid Female
Ovary with eggs
Oviducal gland
Nidamental glands
Oviducal opening
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Squid
VIRTUAL SQUID DISSECTION
• http://www.biologyc
orner.com/workshee
ts/squid_virtual.html
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Octopus
• Eight arms with
suckers
• Crawl or eject
water from siphon
• Change skin color
– chromatophores
• Most intelligent
invertebrate
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Giant Octopus vs shark
• http://video.national
geographic.com/vide
o/player/animals/inv
ertebratesanimals/octopusandsquid/octopus_giant
_kills_shark.html
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WOW, Giant Octopus!
• http://www.youtube.
com/watch?v=lwAqh
Thd_EQ
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Intelligent Octopus
• http://www.youtube.
com/watch?v=bBe2K
aRuI80
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Nautilus
• Indian & Pacific
Ocean @ ~ 1,800
feet
• Avg. life span = 20
years ( unusual –
most cephalopods
have short life span)
• Average size 8-10
inches in diameter
• Up to 94 tentacles
– No suckers
• Shell with many
chambers
– Lives in outermost
chamber
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Nautilus
• http://www.youtube.
com/watch?v=QMFq
V4SJLWg
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Cuttlefish
• http://www.youtube.com/watch?v=2x8v1mxpR0&feature=related
• http://www.youtube.com/watch?v=__X
A6B41SQQ&feature=related
• http://www.youtube.com/watch?v=v8A
w7QroV78 mating in mozambique
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Cephalopod – Master of Disguise
• http://www.youtube.
com/watch?v=5rqho
mPaxhE
• http://www.youtube.
com/watch?v=IyeKb
RIQTxs&feature=rel
ated
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The End
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