Transcript platy mollusca annelidax

30.3 The Trochozoa
• Bilaterally symmetrical at least in some stage of their development
• As embryos, they have three germ layers
• As adults, they have the organ level of organization cilia
• Protostomes
• Trochophores
• Flatworms, rotifers, molluscs, and annelids
trochophore
larvathe
• Either have trochophore larvae today or an ancestor had
one on
past
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cilia
trochophore larva
30.3 The Trochozoa
• Flatworms: Phylum Platyhelminthes
• Incomplete digestive tract and only one opening, the
mouth
• No body cavity – mesoderm fills spaces between organs
• Free-living planarians
• Have muscles and excretory, reproductive, and digestive systems. They
have all organs except respiratory and circulatory organs (diffusion).
• The flat body facilitates diffusion of oxygen and other molecules from cell
to cell.
Parasitic flukes and tapeworms
30.3 The Trochozoa
• Free-living Flatworms
• Freshwater planarians
• Found in lakes, ponds, and streams
• Feed on small organisms such as worms and crustaceans
• Possesses an excretory system (flame cell system)
• Ladder-like nervous system exhibits cephalization
• Reproduce both asexually and sexually
• Regeneration (asexual)
• Hermaphroditic cross-fertilization (sexual)
Planarian Anatomy
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gastrovascular cavity
eyespots
pharynx extended through mouth
auricle
a. Digestive system: Three-branched
system
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Planarian
Anatomy
gastrovascular cavity
eyespots
pharynx extended through mouth
auricle
flame cell
fluid
a. Digestive system: Three-branched
system
cilia
flame cell
excretory canal
excretory pore
b. Excretory system: Flame-cell system
ovary yolk sperm
gland duct
testis
genital pore
c. Reproductive system: Hermaphroditic system
brain
lateral nerve cord
transverse nerve
d. Nervous system: Ladder-style system
eyespots
auricle
5 mm
e.
© Tom E. Adams/Peter Arnold
30.3 The Trochozoa
• Parasitic Flatworms
• Tapeworms (class Cestoda)
•
•
•
•
•
Endoparasites
Range in length from several millimeters to 20 meters
Tough outer tegument to protect from host’s enzymes
Scolex - has hooks for attachment; not a sucker
Body of segments called proglottids
• Organs of both sexes in each proglottid
• Proglottids filled with fertilized eggs are called gravid
• Primary and secondary hosts
Life Cycle of a Tapeworm, Taenia
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hooks
proglottid
2. Bladder worm attaches
to human intestine
where it matures into a
tapeworm.
1. Primary host ingests meat
containing bladder worms.
6. Rare or uncooked meat
from secondary host contains
many bladder worms.
scolex
1.0 mm
sucker
250 m
3. As the tapeworm grows, proglottids mature, and eventually fill with eggs.
5. Livestock may ingest the eggs,
becoming a secondary host as
each larva becomes a bladder
worm encysted in muscle.
(proglottid): © John D. Cunningham/Visuals Unlimited; (scolex): © James Webb/Phototake
4. Eggs leave the
primary host in
feces, which may
contaminate water
or vegetation.
30.3 The Trochozoa
• Parasitic Flatworms
• Flukes (class Trematoda)
• Endoparasites of various vertebrates
• Blood, liver and lung flukes
•
•
•
•
•
•
Two suckers: one for feeding, one for attachment
Alimentary canal is well developed
Muscles and excretory system much like free-living flatworms
Poorly developed senses
Hermaphroditic
Complex life cycle involving two intermediate hosts
Schistosomiasis
30.3 The Trochozoa
• Molluscs (phylum Mollusca)
• Second most numerous animal phylum
• Includes chitons, limpets, slugs, snails, abalones, conchs,
nudibranchs, clams, scallops, squid, and octopuses
• True coelom
• Bilateral symmetry
• 3 germ layers
• Organ level of organization
• Complete digestive tract
30.3 The Trochozoa
• Molluscs
• Unique characteristics of molluscs
• Three distinct parts:
• Visceral mass: includes most organs
• Foot: muscular portion used for locomotion
• Mantle: covering that almost encloses visceral mass
• Mantle cavity - space between the two folds of the mantle
• Mantle may secrete a shell
• Radula - rasping organ for feeding
Diversity of Molluscs
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shell
eyes
tentacles
on mantle
valve
b. Scallop, Pecten sp.
tentacle
eye
arm
gills
mantle
foot
suckers
c. Nudibranch, Glossodoris macfarlandi
d. Two-spotted octopus, Octopus bimaculoides
b: Courtesy Larry S. Roberts; c: © Kenneth W. Fink/Bruce Coleman, Inc.; d: © Ken Lucas/Visuals Unlimited
30.3 The Trochozoa
• Gastropods (class Gastropoda)
•
•
•
•
•
Nudibranchs, conchs, and snails
Foot is flattened ventrally
Move by muscle contractions along the foot
Some are herbivores, others carnivores
Nudibranchs (sea slugs)
• Lack shell
• Conchs and snails have a shell
• Protection
• Prevents desiccation in land snails
Nudibranchs
Conch Shell
Gastropod and Cephalopod Anatomy
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eye
hermaphroditic
gland
shell
cerebral
ganglion
tentacle
radula
pedal
ganglion
penis
foot
Gastropod and Cephalopod Anatomy
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growth
line
eyes
spiral
shell
a. Land snail
© Farley Bridges;
foot
30.3 The Trochozoa
• Cephalopods (class Cephalopoda)
• Squid, octopus, nautilus
• Foot has evolved into funnel or siphon
• Powerful beak and radula for feeding
• Cephalization is apparent
• Octopuses have no shell, squid have reduced shell
• Octopuses thought to be among the most intelligent invertebrates
Squid
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Fig. 30.11d
fin
mantle
pen
suckers
gill
ink sac
arm
anus
funnel
eye
tentacle
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Fig. 30.11e
tentacles
with
suckers
fins
eye
b. Squid
© Georgette Douwma/Photo Researchers, Inc.
Octopus
Octopus
Giant Squid
Swimming Nautilus
Gastropod and Cephalopod Anatomy
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eye
hermaphroditic
gland
shell
fin
cerebral
ganglion
pen
mantle
suckers
gill
tentacle
ink sac
arm
radula
anus
pedal
ganglion
funnel
penis
eye
growth
line
eyes
foot
spiral
shell
a. Land snail
tentacles
with
suckers
fins
eye
foot
tentacle
b. Squid
a: © Farley Bridges; b: © Georgette Douwma/Photo Researchers, Inc.
30.3 The Trochozoa
• Bivalves (class Bivalvia)
• Clams, oysters, scallops, mussels
• Two-part shells secreted by mantle
• Filter-feeders: water enters through incurrent siphon
• Visceral mass
• Coelom is reduced
• Pericardial cavity is the only remains of the coelom
• Described as an open circulatory system because blood flows through sinuses in organs
• Sexes separate – trochophore larvae in marine clams
Clam, Anodonta
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pericardial cavity
umbo
anterior aorta
heart
kidney
posterior ganglion
posterior retractor muscle
digestive gland
posterior adductor muscle
stomach
anterior adductor muscle
posterior aorta
esophagus
shell
anterior ganglion
anus
mouth
excurrent siphon
labial palps
incurrent siphon
foot ganglion
foot
gill
gonad
intestine
mantle
Scallop-adductor muscle
16-30
Oyster bed
16-31
Oyster
16-32
Pearls
16-33
30.3 The Trochozoa
• Annelids (phylum Annelida)
•
•
•
•
•
•
Only trochozoan with segmentation and a well-developed coelom
Hydrostatic skeleton
Specialization of digestive tract
Closed circulatory system
Brain with nerve cord connecting ganglia in each segement
Excretory system – nephridia in most segements
• Tubule for collecting waste material
30.3 The Trochozoa
• Polychaetes
• Have many setae or bristles
• Anchor worm or help in locomotion
• Used for swimming and respiration
• Active predators or sessile forms
• Trochophore larva
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sensory
projections
parapodia
a. Clam worm, Nereis
© Heather Angel/Natural Visions;
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sensory
projections
pharynx
(extended)
sensory
projections
jaw
eyes
parapodia
parapodia
a. Clam worm, Nereis
b. Head region of Nereis
spiraled
tentacles
c. Christmas tree worms,
Spirobranchus
a: © Heather Angel/Natural Visions; c: © Diane R. Nelson
30.3 The Trochozoa
• Oligocaetes (class Oligochaeta)
•
•
•
•
•
•
•
Includes earthworms
Few setae per segment
Head is not well developed
Gas exchange is across the body wall
Scavengers on dead or living organic matter
Evidence of segmentation in many systems
Hemraphroditic
• Clitellum
• No larval stage
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pharynx
brain
mouth
esophagus
coelom
hearts (5 pairs)
crop
seminal vesicle
dorsal blood vessel
nephridium
ventral blood vessel
ventral nerve cord
anus
clitellum
a.
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dorsal blood vessel
coelomic
lining
circular muscles
longitudinal
muscles
muscular wall
of intestine
nephridium
typhlosole
setae
coelom
ventral
blood vessel
ventral nerve cord
subneural blood vessel
b.
cuticle
excretory
pore
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clitellum
anterior end
clitellum
anterior end
c.
© Roger K. Burnard/Biological Photo Service
30.3 The Trochozoa
• Leeches (class Hirudinea)
•
•
•
•
•
Most live in freshwater
No setae
2 suckers – one around mouth, large posterior one
Some free-living but most are fluid feeders
Hirudin prevents blood coagulation
Leeches
Medicinal Leeches