Transcript Phylum Mollusca

Phylum Mollusca
Phylum Mollusca
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Protostomes
Lophotrochozoan group
Eucoelomates (coelomates)
Tridacna gigas
Tridacna squamosa
Phylum Mollusca
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Soft Bodied
Shelled
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Some without
Cephalization
Sensory organs
 Mouths
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Body Divisions
Visceral Mass
 Head-Foot
 Mantle
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Tonicella lineata
Phylum Mollusca
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Complete digestive tract
Digestive glands
Specialized feeding
structures
Circulatory system
Octopus briareus
Heart (2 chambers)
 Open system in most
groups
 Closed in cephalopods
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Coelom restricted to pericardium in most cases
Phylum Mollusca
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Advanced nervous system
Brain
 Sensory organs
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Eyes (simple and camera)
 Sensory papillae
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Excretory system
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Kidney-like nephridia
Reproduction
Monoecious and dioecious
 External development
 External & internal
fertilization
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Mollusc Phylogeny
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~50-80K extant
species
~40K extinct
species
Fossil records
from precambrian
period of
proterozoic eon
(>570my BP)
Mollusc
Phylogeny
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Mantle secreting
shell
Muscular foot
Chambered heart
Mollusc Taxonomy
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Major classes
 Polyplacophora
 Chitons
Chiton tuberculatus lives in
the rocky intertidal zones
eat algae with its radula
8 shell plates
Mollusc Taxonomy
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Atlantic triton’s trumpet
(Charonia variegata)
Major classes
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Polyplacophora
 Gastropoda
 Subclasses:
 Prosobranchia
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Shelled marine
gastropods
Tiger cowrie (Cypraea tigris)
Mollusc Taxonomy
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Spotted sea hare (Aplysia dactylomela
Major classes
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Polyplacophora
 Gastropoda
 Subclasses:
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Prosobranchia
 Opisthobranchia
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Sea slugs (marine)
Phidiana hiltoni
zebra sea goddess
(Hypselodoris zebra)
Mollusc Taxonomy
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Helminthoglypta walkeriana
Major classes
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Polyplacophora
 Gastropoda
 Subclasses:
Prosobranchia
 Opisthobranchia
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 Pulmonata
Terrestrial
snails/slugs
 Freshwater
snails
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Giant banana slug
(Ariolimax columbians)
Mollusc Taxonomy
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Major classes
Bay scallop (Aequipecten irradians)
Polyplacophora
 Gastropoda
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 Bivalvia
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Clams, oysters,
mussels, scallops
Edible mussels
(Mytilus edulis)
Ostrea edulis
Mollusc Taxonomy
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Giant cuttlefish (Sepia latimanus)
Major classes
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Polyplacophora
Gastropoda
Bivalvia
Octopus sp
 Cephalopoda
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Octopus, squid, nautilus
Nautilus sp
Mollusc Taxonomy
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Major classes
Polyplacophora
 Gastropoda
 Bivalvia
 Cephalopoda
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Minor classes
Monoplacophora
 Solenogastres
 Caudofoveata
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Generalized Mollusc Anatomy
Gastropod Feeding
Apparatus
Respiration: Gills
Shell Structure & Formation
A Pearl Among the Swine
Mollusc Reproduction & Development
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Indirect development
Larval stages
 Trochophore larva
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Free swimming, ciliated, shell formation begins
Veliger larva
Free swimming, ciliated velium forms,
 Shell/body torsion occurs
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Spat
Metamorphic form between veliger and juvenile
 Shell elaborates
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Trochophore Larva
Gastropod Veliger Larva
Mouth
Velia
Shell
Veliger
Zygote
Trochophore
Juvenile
Spat
Adult
Adult Abalone
Class Polyplacophora - chitons
Polyplacophoran Anatomy
Class
Gastropoda
The Shell Game
Class Gastropoda - Torsion
Gastropod Shell
Coiling
Gastropod
Gill/Mantle Cavity
Evolution
Generalized Gastropod Anatomy
Marine Gastropods
Cowries
Marine Gastropods
Sea Hare – Aplysia sp
Marine Gastropods - Nudibranch
Terrestrial Gastropods
- Pulmonata
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The mantle cavity serves
as a “lung”
Glandular epidermis
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Secrete mucus (slime)
upon which gastropod
glides
Terrestrial Gastropod - Pulmonata
Pneumostome
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Slugs lack
shells
Mantle thickened
Pneumostome
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Air intake into mantle cavity
Phylum Mollusca, Class Bilvalia
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Two shells
Incurrent & excurrent siphons
No cephalization
Generalized Bivalve Anatomy
Generalized Bivalve Anatomy (XS)
Bivalve Anatomy (Sagittal)
Bivalves are Typically Filter Feeders
Bivalve Life Cycle
Glochidia – Unique Larval Stage of
Freshwater Bivalves
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Internal fertilization
Early development in brood
chamber (region of mantle
cavity)
Release of glochidia veliger
larvae
Glochidia attach to gills of
fish and are distributed
Phylum Mollusca, Class Cephalopoda
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Closed circulatory system
Shell: lost in Octopus, extremely reduced and
enclosed in mantle in squid, planar spiral in
Nautilus
Cephalization
eye
 Beak around
mouth
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Tentacles/arms
Cephalopod Anatomy
Squid are the largest Cephalopods
Nautilus Anatomy
Cephalopod Eye
Mating
Direct Development in Cephalopods
Color & Morphology Changes for
Camouflage