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What is a flatworm?
Flatworms
Acoelomates
Thin, solid bodies
Can be 1mm to several meters
14,500 species
Marine and freshwater and
moist habitats on land
Ex. Tapeworms, flukes,
planarians
1.
Class Tubellaria (Planaria)
Soft, flattened bodies covered in cilia
Live in aquatic or moist environments.
Scavengers.
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2. Class Trematoda (Flukes)
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3. Class Cestoda (Tapeworm)
Parasitic: therefore, they have a tough outer covering and
two suckers to anchor to a host and feed at the same time.
Example: Schistosoma (liver fluke).
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Parasitic: live in digestive tract of host.
Organization
Motility
3 true cell layers (endoderm, mesoderm, ectoderm)
All:
Simple organs (cephalization, excretory, pharynx, etc.)
Bilateral symmetry
Acoelomates
Mobile
Planaria:
move by gliding over a slime track they secrete
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Feeding
Planaria / Flukes:
Extracellular digestion: enzymes secreted by
mouth
A muscular tube, the pharynx, is extended out
through the mouth. The food is sucked in through
the pharynx and passes into the intestine and
digestive glands.
Tapeworm:
Intracellular digestion: tapeworms absorb the
digested nutrients of their hosts, so they have no
need of a mouth.
Digestion / Excretion
Planarians / Flukes
Incomplete digestive system: food enters
through the same opening by which
undigested wastes leave.
Extracellular digestion: enzymes secreted onto
slow-moving or dead prey.
Excretory system consists mainly of FLAME
CELLS; small, bulb-like structures that remove
water and chemical wastes through the body
pores by using beating cilia.
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Digestion / Excretion Con’t.
Tapeworm
No digestive
system, since they
absorb nutrients
already digested by
their host. The
SCOLEX is a knobshaped head with
hooks or suckers or
both, with which
the tapeworm
attaches to its host.
Nervous System
Planaria / Flukes:
Two anterior ganglia serve as a simple brain (cephalization)
A ladder-like network of nerves runs the length of the body
React to light, chemical, food
Nervous System Con’t.
Tapeworm:
None
Reproduction
Planaria / Flukes
1.
Asexual: through fragmentation &
regeneration.
2.
Sexual: individuals are hermaphrodites,
but individuals cannot fertilize their own
eggs. Eggs are laid in a protective cocoon
and take 2-3 weeks to hatch.
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Reproduction Con’t.
Tapeworm:
Behind the SCOLEX is a
region from which
PROGLOTTIDS are
produced and eventually
shed. PROGLOTTIDS are
body sections that contain a
complete hermaphrodite
reproductive system.
Tapeworms have at least
two hosts in their life cycles.
Circulation
Planarains / Flukes / Tapeworms:
None
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Tapeworm
Structure Function
a section of the tapeworm body
Contains male and female reproductive
organs
Able to self- or cross-fertilize
The Proglottids at the end of the body break
off and pass out in feces of host
Each Proglottids contains many fertilized
eggs
Head:
Beef Tapeworm Life Cycle
Proglottids:
has hooks and four suckers for attachment
to gut wall
New Proglottids formed from the head
Cuticle:
Protective outer covering to avoid being
digested by host enzymes
Fish Tapeworm Lifecycle
Pork Tapeworm Lifecycle
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Schistosomiasis
Life Cycle
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