1 unit 6.1 phylum mollusca. 2 mollusks 50,000 -100,000 living species 35,000 extinct species largest...
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Unit 6.1
Phylum Mollusca
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Mollusks
• 50,000 -100,000 living species
• 35,000 extinct species• Largest = 1000 pounds• 80% less than 5 cm• Soft body• Most have a shell• Most marine• Snails terrestrial
– Most habitat
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Phylum Mollusca
• Ventral Foot– Locomotion
• Mantle– Encloses body cavity
• Shell – created by mantle
• Coelom (eucoelomate)• Visceral mass contains
contains organs of digestion, circulation, excretion, & reproduction
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Phylum Mollusca
• Radula – rows of posteriorly oriented teeth. Basically a tongue with teeth
• Open circulatory system– Closed in cephalopods
• Mantle cavity – opens to the outside and functions in gas exchange
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Economically Important
• Pearls• Burrowing shipworms • Snails & slugs
– Garden pests– Food– Intermediate hosts for
parasites
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Trochophore Larva• Same type as Phylum
Annelida• Shows phylogenetic
relationship to higher taxa
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MyxozoaMyxozoaMyxozoaMyxozoa
ArthropodaArthropodaArthropodaArthropoda AnnelidaAnnelidaAnnelidaAnnelida
MolluscaMolluscaMolluscaMollusca
LophophoresLophophoresLophophoresLophophores
HemichordataHemichordataHemichordataHemichordata
VertebrataVertebrataVertebrataVertebrata
Other Other pseudocoelomatespseudocoelomates
Other Other pseudocoelomatespseudocoelomates
NematodaNematodaNematodaNematoda
PoriferaPoriferaPoriferaPorifera
CtenophoraCtenophoraCtenophoraCtenophoraCnidariaCnidariaCnidariaCnidaria
PlacozoaPlacozoaPlacozoaPlacozoa
PlatyhelminthesPlatyhelminthesPlatyhelminthesPlatyhelminthesNemerteaNemerteaNemerteaNemertea
CiliophoraCiliophoraCiliophoraCiliophoraSarcomastigophoraSarcomastigophoraSarcomastigophoraSarcomastigophora
MicrosporaMicrosporaMicrosporaMicrosporaApicomplexaApicomplexaApicomplexaApicomplexa
MesozoaMesozoaMesozoaMesozoa
EchinodermataEchinodermataEchinodermataEchinodermata
CrustaceaCrustaceaCrustaceaCrustaceaChelicerataChelicerataChelicerataChelicerata
UniramiaUniramiaUniramiaUniramia
Other ChordataOther ChordataOther ChordataOther Chordata
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Generalized Mollusk
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Body PlanBody Plan
Mantle cavityMantle cavityMantle cavityMantle cavity
CtenidiumCtenidiumCtenidiumCtenidium
Pericardial cavityPericardial cavityPericardial cavityPericardial cavity MetanephridiumMetanephridiumMetanephridiumMetanephridium
RadulaRadulaRadulaRadula
GonadGonadGonadGonad
Stomach and digestive glandStomach and digestive glandStomach and digestive glandStomach and digestive gland FootFootFootFoot
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Dorsal mantle covers the visceral mass.
Dorsal mantle covers the visceral mass.
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Secretes the shellSecretes the shell
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Ctenidium (Respiration)Ctenidium (Respiration)
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Complete digestive systemComplete digestive system
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Paired ventral nerve cordsPaired ventral nerve cords
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RadulaRadula
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Source: From A Life of Invertebrates, Copyright © 1979 W. D. Russell-Hunter.
Radular Structure
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Coelom - metanephridiaCoelom - metanephridia
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Class PolyplacophoraChitons
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Class PolyplacophoraClass Polyplacophora
• Eight dorsal plates• Fishy flavor & tough
to chew• Reduced head• Radula reinforced
with iron– Scrape algae from
rocks
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Class Polyplacophora
Mantle cavityMantle cavityMantle cavityMantle cavityMouthMouthMouthMouth
CtenidiumCtenidiumCtenidiumCtenidium
FootFootFootFoot
AnusAnusAnusAnus
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Class PolyplacophoraClass Polyplacophora
MouthMouthMouthMouth
DigestiveDigestiveglandgland
DigestiveDigestiveglandgland
StomachStomachStomachStomach GonadGonadGonadGonadPericardial cavityPericardial cavityPericardial cavityPericardial cavity
NephridiumNephridiumNephridiumNephridium
AnusAnusAnusAnus
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Class BivalviaClams, Oysters, Mussels, & Scallops
Class BivalviaClams, Oysters, Mussels, & Scallops
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Class Bivalvia
• Two shells actually form as a single structure
• Most are filter feeders – helpful in removing bacteria from polluted waters
• No head or radula• Burrowing animals
– Sand, wood, rocks
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Giant Clam & Burrowing Clam
Muscular Foot
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Zebra Mussel
• Environmental Pest• Ballast water of ships
from Europe in 1986• Attach 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• Attach to native
mussels• Killed all native
mussels in Lake Erie
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Distribution of Zebra Mussel
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Bivalve structuresBivalve structures
IncurrentIncurrentsiphonsiphonIncurrentIncurrentsiphonsiphon
CtenidiumCtenidiumCtenidiumCtenidium
ExcurrentExcurrentsiphonsiphonExcurrentExcurrentsiphonsiphon
HingeHingeHingeHinge
FootFootFootFoot
Labial palpLabial palpLabial palpLabial palp
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Clam anatomyClam anatomyPericardial cavityPericardial cavityPericardial cavityPericardial cavity
HeartHeartHeartHeart
GonadGonadGonadGonadIntestineIntestineIntestineIntestine
StomachStomachStomachStomach IncurrentIncurrentIncurrentIncurrent
ExcurrentExcurrentExcurrentExcurrent
IntestineIntestineIntestineIntestine
MetanephridiumMetanephridiumMetanephridiumMetanephridium
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Clam anatomyClam anatomy
GonadGonadGonadGonadIntestineIntestineIntestineIntestine
StomachStomachStomachStomachIncurrentIncurrentIncurrentIncurrent
ExcurrentExcurrentExcurrentExcurrent
DigestiveDigestiveglandgland
DigestiveDigestiveglandgland
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Clam anatomyClam anatomyPericardial cavityPericardial cavityPericardial cavityPericardial cavity
HeartHeartHeartHeart
IncurrentIncurrentIncurrentIncurrent
ExcurrentExcurrentExcurrentExcurrent
IntestineIntestineIntestineIntestine
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Clam anatomyClam anatomyPericardial cavityPericardial cavityPericardial cavityPericardial cavity
HeartHeartHeartHeart
GonadGonadGonadGonad
IncurrentIncurrentIncurrentIncurrent
ExcurrentExcurrentExcurrentExcurrent
IntestineIntestineIntestineIntestine
MetanephridiumMetanephridiumMetanephridiumMetanephridium
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Oysters
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• Able to form pearls – the color depends on prevalent minerals in water
• Only eat oysters during cold months – less bacteria in filtrate
• Can cause severe wounds and Vibrio infections
• Use extreme caution when exiting boats in oyster infested waters
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Vibrio vulnificus
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Pearl formation
Developing pearlDeveloping pearlDeveloping pearlDeveloping pearl
EpitheliumEpitheliumEpitheliumEpithelium
ShellShellShellShell
An irritant, usually sand, becomes lodged between the shell and mantle. Layers of shell are then secreted by the mantle around the foreign material. The mineral content of the water determines the color of the resulting pearl.
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Scallops
• Good swimmers – the only migratory bivalve
• Movement achieved by rapidly opening and closing shell
• Mostly free-living• Highly regular and
geometrically symmetrical shells
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Shipworms• Highly reduced shells.• Known as termites of the
sea.• Burrow into any submerged
wooden structure including ships, docks, & piers.
• Special gland called Deshayes gland contains bacteria that allow shipworms to digest cellulose
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Shipworms
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Class GastropodaSnails, Slugs, Conchs, Abalones, & Limpets
Class GastropodaSnails, Slugs, Conchs, Abalones, & Limpets
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Class Gastropoda
• One shell (if present)• Torsion of body –
allows head to retract before tail, allows clean water to enter mantle cavity, and orients sensory organs in direction of forward movement.
• Largest & most varied molluscan class
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Torsion
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Snails
• Terrestrial is most encountered type but marine varieties are much more numerous.
• Mantle cavity functions as lung in terrestrial snails.
• Herbivores, omnivores, and carnivores.
• All land snails are hermaphrodites.
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Snails
TentacleTentacle(Eye stalks)(Eye stalks)TentacleTentacle(Eye stalks)(Eye stalks)
TentacleTentacleTentacleTentacle
PneumostomePneumostomePneumostomePneumostome
AnusAnusAnusAnus
FootFootFootFootMouthMouthMouthMouth
Genital poreGenital poreGenital poreGenital pore
ShellShellShellShell
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Internal Structure of a Generalized Gastropod
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Nudibranchs
• No shell – commonly called sea slugs
• Dorsal projections aid in respiration and protection – they eat hydroid cnidarians, conserve the nematocysts, and move them to the dorsal projections
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Nudibranchs• Some of the most colorful
creatures on earth.• Unlike most other
gastropods, they are bilaterally symmetrical.
• One species of nudibranch is the only animal that can photosynthesize. However, it must also eat to satisfy all of its energy needs.
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Nudibranchs
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AbalonesAbalones
• Several holes in top of shell– Excrete waste– Used for respiration
• Shell is incredibly strong. It is made of microscopic calcium carbonate tiles stacked like bricks.
• Live primarily on cooler waters.
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Abalones
• Source of food and decoration – the inner part of the shell is highly iridescent and used for mother-of-pearl inlays.
• Cling to rocks in subtidal zone and feed on primarily red algae.
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Slugs
• No shell• Garden pests• Bodies are prone to
desiccation – confined to moist environments
• Secrete mucous to help prevent desiccation and to protect themselves against predation.
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Limpets
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• Gastropods with conical shaped shells
• Attach to rocks or other hard substrates in intertidal zones.
• Contain gills and lungs to survive in intertidal zone.
• May be eaten in certain parts of the world.
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Conchs
• Large shell with highly spiraled character
• All species are marine• Conchs are found in the
Indian & Pacific oceans as well as in the Caribbean sea.
• Their meat is used as food and their shells are highly prized as decorations.
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Class CephalopodaSquids, Octopi, Nautiluses
Class CephalopodaSquids, Octopi, Nautiluses
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Class Cephalopoda
• Shell in squid and octopus absent or vestigial. Present in nautilus.
• Movement via jet propulsion
• Ink sac used for defense• Foot modified into arms
and tentacles• All marine and predatory.
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SquidSquid
DorsalDorsalVentralVentral
Posterior surfacePosterior surface
RightRight
LeftLeft
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Squid• Have 8 arms and two
tentacles.• Siphon allows jet
propulsion in both directions along the axis of the animal.
• Swimming fins located on either side of the mantle.
• Giant axon is the largest neuron in the animal kingdom
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SquidSquid
FinFinFinFin
ArmArmArmArm
Funnel (siphon)Funnel (siphon)Funnel (siphon)Funnel (siphon)
EyeEyeEyeEye
TentacleTentacleTentacleTentacle
CollarCollarCollarCollar
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SquidSquidShell (Pen)Shell (Pen)Shell (Pen)Shell (Pen)
CtenidiumCtenidiumCtenidiumCtenidium
FunnelFunnelFunnelFunnel
SystemicSystemicheartheartSystemicSystemicheartheart
Branchial heartBranchial heartBranchial heartBranchial heart
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Squid MaleSquid MaleTestisTestisTestisTestis
Hectocotylous armHectocotylous armHectocotylous armHectocotylous arm
PenisPenisPenisPenis
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Squid FemaleSquid Female
Ovary with eggsOvary with eggsOvary with eggsOvary with eggs
Nidamental glandsNidamental glandsNidamental glandsNidamental glands
Oviducal glandOviducal glandOviducal glandOviducal gland
Oviducal openingOviducal openingOviducal openingOviducal opening
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cephalopod Eye
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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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Chromatophores
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Nautilus• Up to 94 tentacles
– No suckers
• Shell with many chambers – lives in outermost chamber.
• Considered to be a living fossil.
• Can alter the amount of gasses in shell chambers thus controlling its position in the water column.
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Nautilus
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Class Scaphopoda
• Tooth shells• Shell opens on both
ends• Burrow into mud• No gills
– Mantle for gas exchange
• Feed on detritus and protozoa
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Class ScaphopodaClass Scaphopoda
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The End