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3/31/2011
Section 4
S i Deuterostomia
Ecdysozoa
Lophotrochozoa
Cnidaria and Ctenophora
Porifera
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Protostomia
Radiata
Bilateria
Professor Donald McFarlane
Eumetazoa
Parazoa
Lecture 13 Invertebrates: Parazoa,
Radiata, and Lophotrochozoa
Ancestral colonial
choanoflagellate
2
Traditional classification based on
body plans
Parazoa – Phylum Porifera
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2.
3.
4.
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„
„
„
„
Ecdysozoa
Deuterostomia
D
„
Sponges
Loosely organized and lack
tissues
Multicellular with several types of
cells
8,000 species, mostly marine
No apparent symmetry
Adults sessile, larvae freeswimming
Cnidaria and
Ctenophora
„
Lo
ophotrochozoa
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1.
4 main morphological and developmental
features used
Presence or absence of different tissue
types
Type of body symmetry
Presence or absence of a true body
cavity
Patterns of embryonic development
Porifera
Parazoa
„
Protostomia
Bilateria
Radiata
Parazoa
Eumetazoa
Ancestral colonial
choanoflagellate
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Water drawn through pores (ostia) into
spongocoel
„ Flows out through osculum
„ Choanocytes line spongocoel
„
… Sexually
„
and eat small particles and plankton
„
Mesohyl between choanocytes and
epithelial cells
Most hermaphrodites
p
p
producing
g eggs
gg and sperm
p
Gametes are derived from amoebocytes or
choanocytes
… Asexually
… Amoebocytes
absorb food from choanocytes,
digest it, and carry to other cells
… Spicules (skeletal fibers) or spongin
„
Small fragment or bud may detach and form a new
sponge
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Radiata – Phylums Cnidaria
and Ctenophora
Water
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Choanocyte
Fl
Flagellum
ll
Osculum
Epithelial cell
Collar
Nucleus
Amoebocyte
Spicule
… Ectoderm
Spongocoel
Ostium
Radiata
and
endoderm
… Mesoglea
Parazoa
Ecdysozoa
Bilateria
Eumetazoa
connects
layers
Mesohyl
Spicule
(c) Cross section of sponge morphology
Protostomia
… Diploblastic
Water
Deuterostomia
Radial symmetry
„ Mostly marine
„ Only
O l 2 embryonic
b
i germ
layers
„
(b) Typical vase
shape of sponges
Lophotrochozoa
Radiata
Porifera
„
Reproduce
Cnidaria
a and Ctenophora
… Trap
„
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Phylum Cnidaria
„
First clade with true tissues
„ Gastrovascular cavity for extracellular
digestion
g
„
… Allows
… Sessile
polyp – tubular body with tentacles
surrounding opening (mouth and anus)
… Motile medusa – umbrella-shaped body with a
mouth
th on th
the underside
d id surrounded
d db
by
tentacles
ingestion of larger food particles
over sponge’s intracellular digestion
… Advance
„
„
True nerve cells arranged in nerve net
… No
2 different body forms
Cnidocytes contain nemotocysts
… Hairlike
central control organ
… Some
„
trigger – cnidocil
sticky while other sting
Simple muscles and nerves
… Not
true muscles (not of mesoderm origin)
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Tentacle
Mouth/
anus
Phylum Ctenophora
Bell
Epidermis
(from ectoderm)
Mesoglea
Gastrodermis
(from endoderm)
Gastrovascular
cavity
Mouth/
anus
(a) Polyp
Comb jellies
„ Less than 100 species- all marine and look
like jellyfish
„ Eight
Ei ht rows off cilia
ili on surface
f
b
beatt ffor
propulsion
„ 2 long tentacles without stinging cells
„ Colloblasts secrete sticky substance
„ First complete gut – mouth and anus
„ Hermaphroditic
„ Bioluminescent
„
(b) Medusa
Tentacle
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Lophotrochozoa
„
„
„
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Flatworms, rotifers, lophophorates, mollusks and
annelids
Traditionally, bilaterally symmetrical animals split
into those with no coelom (platyhelminthes)
(platyhelminthes),
pseudocoleomate (nematodes and rotifers) and
remaining coelomate phlya
Molecular data suggests a different grouping
with the deuterostomates separate and the
protostomates divided into the Lophotrochozoa
(Platyhelminthes, Rotifera, Lophophorata,
Mollusca and Annelida) and the Ecdysozoa
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Phylum Platyhelminthes
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Lophotrochozoa
Flatworms
„ Lack a specialized
respiratory or circulatory
system to transport gases
„ Respire by diffusion
„ Among first animals with
active predatory lifestyle
„ Bilaterally symmetrical
with a head
Annelida
Ecdysozoa
Deuterostomia
D
Rotifera
Mollusca
Lophophorata
Porifera
Platyhelminthes
Cnidaria an
nd Ctenophora
„
Lophotrochozoa
Protostomia
Radiata
Parazoa
„
Bilateria
„
Eumetazoa
„
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First with 3 embryonic germ layers – triploblastic
Mesoderm key innovation – led to more
sophisticated organs
Acoelomate – lacking fluid-filled cavity
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4 classes
„ Turbellaria – Free-living, Planaria
„ Monogenea – Fish flukes
„ Cestoda – Tapeworms, parasitic
„
Digestive system incomplete
„ Distinct excretory system with
protonephridia and flame cells
„ Light sensitive eyespots or ocelli
„ Cerebral ganglia receive input
„ Retain nerve net with beginning of more
centralized nervous system
„ Sexual or asexual reproduction
„
2 separate host species in life cycle
Trematoda – Flukes, parasitic
… More
complex life cycle with multiple hosts
liver fluke, Clonorchis sinensis
… Blood flukes, Schistosoma spp., most
common parasitic trematode infecting humans
… Chinese
hermaphroditic but do not self fertilize
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Lophophorata
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„
„
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Annelida
Ecdysozoa
De
euterostomia
Mollusca
Rotifera
3 closely related phyla
Phoronida, Bryozoa,
Brachiopoda
All possess a
lophophore – ciliary
feeding device that also
functions in respiration
True coelom
Lo
ophophorata
„
Platyhelminthes
„
Porifera
Lophotrochozoa
Cnidaria an
nd Ctenophora
… Most
…
„
Lophotrochozoa
Protostomia
Radiata
Parazoa
Bilateria
Eumetazoa
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Phylum Mollusca
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… Foot,
„
„
„
„
visceral mass and mantle
Coelom confined to small area
around heart
Open circulatory system
Metanephridia
Radula – unique tongue-like
organ
Deuterostomia
Annelida
Ecdysozoa
Rotifera
Mollusca
Porifera
Lophophorata
„
Platyhelminthes
„
Over 100,000 species
Soft body with, in many species,
protective external shell
Body
ody has
as 3 pa
parts
ts
Cnidaria and Ctenophora
Lophotrochozoa
„
Lophotrochozoa
Protostomia
Radiata
Parazoa
Bilateria
Eumetazoa
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„ Most
shells complex 3 layered and
secreted by mantle
„ Separate sexes although some
hermaphroditic
„ External fertilization – some internal
((key
y to snails colonizing
g land))
„ Trocophore larvae develops into
veliger with rudimentary foot, shell
and mantle
„ 8 classes with 4 common
…Polyplacophorans,
gastropods, bivalves
and cephalopods
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Polyplacophorans – chitons
„ Gastropods – snails, slugs and
nudibranchs
„
Phylum Annelida
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… Most
morphologically complex, fast-swimming
marine predators, closed circulatory system
… Beaklike jaw, only nautilus has external shell,
some have foot modified into muscular siphon
for propulsion
1.
2.
3.
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Repetition of components
provides backup
Coelom acts as hydrostatic
skeleton
Permits specialization
Annelida
Ecdysozoa
E
Rotifera
Mollusca
Deutterostomia
„
Lophotrochozoa
Lophophorata
Bivalves – clams, mussels, oysters
„ Cephalopods – octopuses, squids,
nautiluses
„
Rings are distinct
segments separated by a
septum
Segmentation has
advantages
Porifera
„
Platyh
helminthes
class, shells can be reduced or lost,
most marine or freshwater but some
colonized land
Cnidaria and Ctenophora
… Largest
Lophotrochozoa
Protostomia
Radiata
Parazoa
Bilateria
Eumetazoa
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Digestive system complete and
unsegmented
„ Sexual reproduction involves 2 individuals
(sometimes separate sexes, others
hermaphroditic) with internal fertilization
„ Asexual reproduction by fission
„ 15,000 species
„ All annelids except leeches have setae on
each segment
„
„
Double transport
system
…
Circulatory
system and
d
coelomic fluid
carries nutrients,
wastes and
respiratory gases
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2 classes
„ Polychaeta – marine worms
„
… Most
„
species rich, many long setae
Clittelata
… Subclass
Oligochaeta – terrestrial and
freshwater worms (earthworms)
„
Role in conditioning soil through castings
… Subclass
„
Hirudinea – leeches
Primarily freshwater, hirudin (anticoagulant), may
be used in reattachment surgeries, generally
external parasites
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