Transcript Phylum Platyhelminthes

Phylum Platyhelminthes
Flatworms
Flukes
Tapeworms
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Phylum Platyhelminthes
General Characteristics
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Usually flattened dorsoventrally
Triploblastic
Acoelomate
Bilaterally symmetrical
Unsegmented worms
Cerebral ganglion (“brain”) and longitudinal nerve
cords
Protonephridia (excretory structures)
Hermaphroditic (monoecious)
Phylum Platyhelminthes
Planaria Basics
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https://www.youtube.com/watch?v=cHoAFihJG
bM
Phylum Platyhelminthes
Nervous System
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Free-living species usually have a
well-developed sensory system
Parasites generally have less
elaborate systems.
WHY?
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Phylum Platyhelminthes
Flatworm Body Plans
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Parenchyma tissue (loose tissue derived from
mesoderm)
Gastrodermal cells comprise digestive cavity-secrete
enzymes that aid in digestion
Triploblastic
Phylum Platyhelminthes
Digestion and Excretion
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Mouth is usually located
at the posterior end or
mid-body on ventral
surface
http://www.youtube.com/w
atch?v=w0QzSYQGsnA’
Excretory system
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Contains flame cells
which collect excess
water and nitrogen
waste. Excreted through
pores.
Phylum Platyhelminthes
Regeneration
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Many species posses remarkable powers of
regeneration and repair wounds
Phylum Platyhelminthes
Reproduction
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Almost all are simultaneous
hermaphrodites
Parasitic species (flukes and
tapeworms) have complex
lifecycles, with various hosts
and several different larval
stages
Incredible powers of
regeneration
Phylum Platyhelminthes
Reproduction
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Asexual reproduction occurs through a process called
transverse fission
Sexual Reproduction occurs with the exchange of
sperm
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http://video.nationalgeographic.com/video/animals/invertebrat
es-animals/other-invertebrates/weirdest-flatworms/
Fertilized eggs are released and usually develop
directly into flatworms
– Muller's larva
Phylum Platyhelminthes
Exhanges with the environment
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Gases exchanged by diffusion through body
wall
Wastes removed by diffusion
Protonephridia-fine tubules that run the length
of the body
Side branches of the tubules have flame cells
with cilia that drives fluid down through the
tubule and to the outside of the body through
nephridiopores.
Phylum Platyhelminthes
Taxonomic Summary
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Phylum Platyhelminthes
(Flatworms)
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Class Turbellaria
Class Cestoidea
Class Trematoda
Class Monogeneans
Phylum Platyhelminthes
Class Turbellaria
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Most are free–living,
tiny and
inconspicuous
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Free-living
Flatworm
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Primarily marine and
freshwater
Predators and
scavengers
Ex: Planaria
Phylum Platyhelminthes
Turbellarian Lifestyles
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Named for turbulance caused by beating cilia
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Glide using cilia and muscular undulations
Secrete mucus that aids in adhesion and helps cilia
gain traction
Most are benthic
Posses several nerve cords with a centralized
ganglia (brain)
http://www.youtube.com/watch?v=XeX0FKqXI7
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Phylum Platyhelminthes
Turbellarian Habits
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Some species also have a protrusible pharynx that
captures food and transfers it into the mouth
– Can be carnivores or scavenge on dead animals and
detritus
Phylum Platyhelminthes
PARASITIC WORMS
Animal host where ADULT feeds and
reproduces = Primary Host
Animal host where LARVAL form lives
and feeds = Intermediate Host
Class Cestoidea (Tapeworms)
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http://www.youtube.com/watc
h?v=SpVLRVoNAbA
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Defining
characteristics
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Scolex
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Proglottids
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Contains hooks used
for anchoring
Long series of
repeating units which
contain reproductive
structures
Phylum Platyhelminthes
Proglottids
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Proglottids
– Each animal can be
3,000 – 4,000 per
animal
– Amazing reproductive
output
– Each may contain
several ovaries and
1,000 distinct testes
Phylum Platyhelminthes
Beef tapeworm
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Phylum Platyhelminthes
Problems of a parasitic existence
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Reproduce within the definitive host (endoparasites)
Get fertilized eggs out of the host
Contact a new and appropriate host
Obtain entrance into the host
Locate the appropriate environment within the host
Maintain position within the host
Withstand an often anaerobic environment
Avoid digestion or attack by the hosts immune system
Avoid killing the host, at least until reproduction is
completed
Phylum Platyhelminthes
Class Trematoda (Flukes)
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All are external and
internal parasites of
other animals
Leech-like bodies with a
sucker at each end
Have a gut and welldeveloped reproductive
system, never
segmented
Phylum Platyhelminthes
Trematoda Lifecycles
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The lifecycle is
complex with up to 4
different hosts and
several larval types
Phylum Platyhelminthes
Trematodes of Concern
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Schistosomiasis
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Deadly prominent disease in
many regions of the world
Bores into the skin of the
definitive host and travels in
the circulatory system to the
heart the lungs and the
kidneys where it feeds and
grows
Inflammation is caused by
eggs becoming trapped in the
hosts tissues
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Chinese liver fluke
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Lives in the bile duct of
humans, cats, and dogs
(1-2 cm.)
Goes through two
intermediate hosts
Infection occurs from
ingestion of raw fish
Phylum Platyhelminthes
Class Monogenea
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Monogenetic flukes – named because they
have only one generation in their life cycle.
(one adult develops from one egg)
Mostly external parasites
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“ectoparasites”
Phylum Platyhelminthes
Additional Vocabulary
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Tegument = Thickened PROTECTIVE layer on
the outside of worms (cellular)
Cuticle = Non-cellular protective coating found
on the outside of worms.
Phylum Platyhelminthes