Download Lophophorates, Mollusca

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Lophophorates
•  Ciliated Lophophore- feeding structure
•  Hollow lophophore tentacles are projections of
the coelom (respiratory)
•  Surrounds mouth
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Phylum Bryozoa
•  “Ectoprocta”
•  4000 species, both
FW and Marine
•  Colonial–  Zoecium
–  Jack-in-the-box
–  operculum
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Phylum Brachiopoda
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•  325 extant, 12,000 extinct
•  Two calcareous shells: Top/bottom, not right/left
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Phylum Mollusca: snails, slugs, chitons,
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clams, octopus and squid
“HAM”
•  Trend toward rounder body: low SA/vol ratio
•  Lack of segmentation (except Neopilina)
•  Hypothetical Molluscan ancestor
–  Mantle and mantle cavity, shell
–  Muscular foot: sensory and locomotory
–  Visceral Mass
•  Cephalization: sensory and feeding
•  Gills (most)
•  Complete GI w/ glands, radula
•  Open circ. system*: heart and haemocoel
•  Metanephridium
•  Separate sexes
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The trochophore larva
Shell and Mantle
3 layers
1.  Periostracum
2.  Prismatic
2nd larval stage-Veliger larva of snail
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3.  Nacreous
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Radula
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Class Monoplacophora
Class Scaphopoda
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Class Polyplacophora: chitons
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Cryptochiton stelleri- Gumboot Chiton
600 living species, mostly intertidal
Most similar to ancestral mollusc
Broad-footed herbivores
8 overlapping plates
Very little cephalization: no eyes or tentacles,
small head w/ radula
Class Gastropoda: snails, slugs, limpets
•  Largest molluscan class, 40,000 species
•  Mobile: Herbivores and Carnivores
•  3 important changes from ancestral mollusc
–  Greater cephalization: affects sensory and locomotion
–  Asymmetrical spiral shell: portable protection
–  Torsion: realignment of body with shell
•  Feeding strategies and specializations
•  Gills or “lungs”
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Torsion- do you see a problem?
(and de-torsion)
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Class Bivalvia: clams
•  Laterally compressed w/dorsal hinge
•  Very large mantle cavity: use of gills for
respiration and suspension (filter) feeding
Pulmonate gastropodsmantle cavity modified
into lung
–  Incurrent and excurrent siphons
•  No radula or distinct head present
•  Pearls: require inner nacreous
layer
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Ctenidia
Internal Anatomy
Highly modified for
respiration AND feeding
Water/Food path
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Burrowing Locomotion
Cl. Cephalopoda: nautilus, squid, octopus
•  650 species, extinct members include Ammonites (65
mya)
•  Predators
•  Swimming lifestyle: jet propulsion
•  Reduced or absent shell
•  Closed circulatory system
•  Cephalization: sensory, movement, learning
•  Foot gives rise to funnel
•  Arms that are probably derived from the molluscan head
•  Chitinous beaks
•  Direct development (larvae?)
•  Cephalopod eye: convergence
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Squid Internal Anatomy
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Giant Squids
Architeuthis
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