Team Two!!!
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Platyhelminthes
(flatworms)
 Rotifera (rotifers) and
Nematoda (round
worms)
 Nemertea (ribbon
worms) and
Lophophorate
Platyhelminthes
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Have bilateral symmetry
 Can be free living or
parasitic which absorb
nutrients from a host
 Have 3 germ layers and
are acoelmate (lacking a
cavity between gut and
outer wall)
 Are protostomes
 Move by using cilia or by
contracting their muscles
Flatworm
Platyhelminthes
Tapeworm
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Free living
platyhelminthesreproduce
asexually by fission and
parasitic platyhelminthes
reproduce sexually and
self fertilize
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The embryo of tapeworms
and other parasitic worms
are called scolex
Platyhelminthes
Schistosoma
Life Cycle-
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-Trichinella Life cycle
Platyhelminthes
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Specalized Tissues
Platyhelminthes have a ventral nerve cord
•
have eye spots that detect the intensity of light
•
have ganglia, which is a mass of nerve cell bodies ( resembles a brain)
•
have a gastrovascular cavity called a pharynx- which is a single opening used as
both a mouth and anus
Examples are tapeworms, flukes, Dugesia,
Dugesia tigrina
Phylum Rotifera
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About 1,800 species
Are tiny animals that mainly inhabit fresh water,
although some live in the sea or in damp soil.
Range in size from about 0.05 to 2 mm (much smaller
compared to other protists.)
Have bilateral symmetry and are truly multicellular.
“Rotifer,” derived from Latin, means “wheel-bearer”—a
reference to the crown cilia that draws a vortex of water
into the mouth.
Examples: Rotaria, Philodina, Keratella, Brachionus,
and Polyarthra.
Phylum Rotifera
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Have specialized organ
systems—including a
complete digestive tract: a
digestive tube with a
separate mouth and anus.
Perform a type of
reproduction called
parthenogenesis: females
producing more females
from unfertilized eggs.
Phylum Rotifera
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Are pseudocoelomate animals—they have a cavity that is
not completely lined by mesoderm-derived tissue.
The fluid in the pseudocoelom serves as a hydrostatic
skeleton and as a medium for the internal transport of
nutrients and waste.
Rotifers may be:
-free swimming
-able to move by inchworming along the substrates
-sessile, living inside tubes or gelatinous holdfasts.
Video: http://www.youtube.com/watch?v=YF8OJt_pujc
Phylum Nematoda
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Roundworms
About 90,000 known species.
Many are free-living soil dwellers that help decompose and recycle
nutrients.
Have bilateral symmetry.
Examples: whipworms, hookworms, pinworms, ascarids, and filarids.
Nematoda
Phylum Nematoda
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Have a complete digestive tract: a
digestive tube with a separate
mouth and anus.
Covered by a tough, transparent
cuticle—the exoskeleton of an
arthropod, consisting of layers of
protein and chitin.
The muscles of nematodes are all
longitudinal, and their contraction
produces a thrashing motion. This
and the cuticle help nematodas to
move.
Are pseudocoelomate animals—
they have a cavity that is not
completely lined by mesodermderived tissue.
Phylum Nematoda
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Reproduction is usually
sexual—females are
generally larger than
males.
Fertilization is internal,
and a female can deposit
100,000 or more fertilized
eggs per day.
The zygotes of most
species are resistant cells
capable of living in harsh
conditions.
Hookworm
Phylum Rotifera and Nematoda
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Are both eumetazoa—they have closely
functioning cells organized into tissues.
 They are triploblastic (contain three germ layers.)
These three layers (ectoderm, mesoderm, and
endoderm) develop into various organs during
embryonic development.
 There is a progressively greater increase in nerve
tissue concentration at the anterior end (head.)
 Both have a complete digestive tract.
Nemertea
-The phylum has
bilateral symmetry
-Has 3 germ layers
-Has a primitive
coelom.
-They use the coelom
(filled with fluid) to
propel themselves
through the water.
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Many live in water, so they
can swim quite well.
 Has a complete digestive
tract and a closed circulatory
system. (blood contained in
vessels)
 However, they have no heart,
the blood is propelled by
muscle squeezing vessels.
Baseodiscus delineatus
Nemertea (cont.)
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Life:
• As a juvenile the
nemertea lives in the
exoskeleton of a crab.
• The size increases as
the crab’s shell
increases.
• They are predators and
will either actively
pursue their prey or sit
and wait for it.
Cerebratulus
Nemertea (cont.)
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Examples:
• Malacobdella lives
parasitically in
molluscs
Deep water ribbon worm.
Tubulanus rhabdotus
The proboscis apparatus is used as
a means of catching food. It
wraps around the food and draws
it in.
Nemertea (cont.)
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Different types of
Nemertea have
different colors,
however their colors
change depending on
where they are. (caves
or exposed).
 Commonly called
ribbon worms.
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The largest type of
Nemertea that has
been found, Lineus
longissimus, stretched
30 m long!
 Normally 10mm100cm long.
Removal of Guinea Worm
http://www.youtube.com/watch?v=mUz9gqLmyQ0
Lophophorate
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Bryozoan
Combines three phyla:
Bryozoans, Phoronids,
Brachiopods.
 All three have a lophophore:
a horseshoe-shaped fold of
the body that has cilia,
surrounding the mouth.
 The three phyla also share a
U-shaped digestive tract and
have no head.
Lophophorate (cont.)
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They have true
coeloms, lined fully
with mesoderm. 3
germ layers.
 Bryozoans and
brachiopods are sessile
while phoronids live
buried in the sand.
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Development:
• Bryozoans- larval;
has radial clevage at
first, and then spiral.
Placed closer to
protostomes, however in
embryonic development
they resemble
deuterostomes.
Lophophorate (cont.)
Phoronopsis californicaphoronid
Phoronis hippocrepia phoronid
Costazia costazi, bryozoan
Onniella meekiBrachiopod
Fresh water Bryozoan with lophophore
extended.
Lophophorate (cont.)
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Bryozoans help build
reefs
 Brachiopods, resemble
clams.
 Phoronids- tubedwelling marine
worms. Tubes made
of chitin!
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Seem to be either
asymmetrical or
bilateral.
Review Game: Platyhelminthes
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What type of symmetry do Platyhelminthes
have?
How do Platyhelminthes move?
How do parasitic platyhelminthes
reproduce?
What is the function of eye spots?
Answers: Platyhelminthes
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What type of symmetry do Platyhelminthes have?
Bilateral Symmetry
 How do Platyhelminthes move? By using cilia or
by contracting their muscles.
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How do parasitic platyhelminthes reproduce?
They reproduce sexually and self fertilize.
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What is the function of eye spots? They detect
the intensity of light.
Review Game: Rotifera and
Nematoda
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What type of symmetry do the phylum
Rotifera and phylum Nematoda share?
What is a complete digestive tract?
What type of reproduction do Rotifers
perform?
Which phylum has a hydrostatic skeleton?
Answers: Rotifera and Nematoda
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What type of symmetry do the phylum Rotifera
and phylum Nematoda share? Bilateral
Symmetry
 What is a complete digestive tract? A digestive
tube with a separate mouth and anus.
 What type of reproduction do Rotifers perform?
Parthenogenesis
 Which phylum has a hydrostatic skeleton?
Rotifera
Review Game: Nemertea and
Lophophorate
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What are the three phyla under
lophophorate? And what do they look like?
What is a proboscis apparatus?
Where do nemerteas grow up?
What is the function of Bryozoans?
Answers: Nemertea and
Lophophorate
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What are the three phyla under lophophorate?
Bryozoans, Phoronids, Brachiopods And what
do they look like? All three have a lophophore.
 What is a proboscis apparatus? It is used as a
means of catching food. It wraps around the
food and draws it in.
 Where do nemerteas grow up? In the
exoskeleton of a crab.
 What is the function of Bryozoans? They help
build reefs.
~THE END~