Download Unit 5.1 - Platyhelminthes - Jutzi

Unit 5.1
Phylum Platyhelminthes
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Phylum Platyhelminthes
• Flat worms
• Triploblastic – three primary
germ layers
• Acoelomate – no body cavity
• Bilateral symmetry
• Hermaphroditic
– Monoecious – Having both sperm
and egg producing parts
• One opening for digestive
system – located ventrally.
Food is eaten and excreted
through the same tube.
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Phylum Platyhelminthes
• Paired lateral nerve
cords & cerebral
ganglion – very simple
• Flame cells –
specialized “kidney”
cells
• No specialized
circulatory or respiratory
systems – must be flat
so nutrients & oxygen
can diffuse throughout
the body
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Uniramia
Echinodermata
Chordata
Lophophorates Chelicerata
Crustacea
Protochordates
Arthropoda
Annelida
Hemichordata
Other
pseudocoelomates
Nematoda
Mesozoa
Sarcomastigophora
Ciliophora
Apicomplexa
Microspora
Mollusca
Nemertea
Platyhelminthes
Ctenophora
Cnidaria
Placozoa
Porifera
Myxozoa
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Acoelomate
Ectoderm
Mesoderm
Endoderm
Coelom – A fluid filled space that is completely
surrounded by mesoderm
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Phylum Platyhelminthes: Class Turbellaria
Acoelomate
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Pseudocoelomate
Ectoderm
Mesoderm
Endoderm
Coelom – A fluid filled space that is completely
surrounded by mesoderm
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Coelomate
Ectoderm
Mesoderm
Endoderm
Coelom – A fluid filled space that is completely
surrounded by mesoderm
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Nervous System
Lateral nerve cord
Cerebral ganglion
Connectives
Eye spot
Auricle
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Brain
Auricle
Cerebral
ganglion
Paired
nerve cords
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Excretory System
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Turbellaria
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Class Turbellaria
• Eye spots – detect
simple light gradients.
• Ciliated skin surface
secretes mucous and
aids in movement.
• May be aquatic or
terrestrial. Terrestrial
species are all nocturnal.
• Most are free-living – not
parasites but
predators/scavengers.
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Class Turbellaria
• Planarians have the ability to
regenerate new body parts or
to generate an entirely new
organism from pieces of
themselves.
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Class Trematoda
• Flukes
• Parasites
• Holdfast devices
– Most possess these
• Complex life cycle
• Intermediate host
– Animal with juvenile stage
• Definitive host
– Animal with adult stage
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Clonorchis sinensis
Oral sucker
Intestine
Uterus
Yolk gland
Ovary
Seminal
recepticle
Testes
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Clonorchis sinensis
• Chinese liver fluke
• 50 million people infected.
• Cirrhosis of liver – liver
tissue is replaced by nonfunctioning scar tissue that
impairs overall liver function
• Diarrhea
• Edema – fluid beneath the
skin.
• Severe gut pain.
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Fascioloa hepatica
• Sheep liver fluke
• Sheep, cattle and
man
– Weight loss
• Eat vegetation
contaminated with
metacercariae – small
capsules that house
the intermediate
stage of the fluke.
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Life Cycle of the Sheep Liver Fluke
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Fasciolopsis buski
•
•
•
•
Intestinal fluke
10 million people
Man and pigs
Hemorrhage and
abscesses of small
intestine
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Paragonimus westermani
• Lung fluke
• Carnivores, pigs,
rodents and man
• May be fatal
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Schistosoma
• Blood flukes – parasitize
mesenteric blood vessels.
• 200 million people infected.
• 1 million deaths/year.
• Second most deadly
parasite behind malaria.
• Males wrap around
females & they exist in
pairs throughout adult
lives.
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Life Cycle of a Schistosome Fluke
Eggs are expelled in urine or feces to fresh water where
the larvae pass through an intermediate stage involving a snail
host and then enter through the skin of a passing human host.
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Schistosoma
• The eggs all have a
hook that tears bodily
tissues throughout the
human host causing
more damage as they
are passed.
• Larvae have a forked
tail that assist them in
borrowing through
human skin.
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Schistosoma
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Swimmers Itch – Related to
Blood Fluke
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Swimmers Itch
• Need avian hosts to
complete their life cycle.
• Humans are
“accidentally” infected
and develop a rash for
around a week.
• Sores develop around
burrowing sites but the
larvae die within a few
hours of entering the
skin
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Class Cestoidea
• Tapeworms
• No digestive system –
suck in pre-digested
nutrients from the
intestines of the host
that are directly utilized
in metabolic processes.
• Can grow up to 100 feet
long. Human
tapeworms may reach
60 feet in length.
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Class Cestoidea
• The scolex, or head, is
equipped with suckers
designed to anchor the
worm to the intestinal
wall and to suck in
nutrients.
• The proglottids are
hermaphroditic
segments, each able to
detach from the body
and produce eggs.
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Class Cestoidea
• Infections are usually
asymptomatic other than
lethargy and/or dull
abdominal pain.
• The lethargy is due to a
lack of nutrients caused by
the tapeworms’ feeding.
This leads to weight loss.
• People may purposefully
infect themselves with
tapeworms to lose weight.
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Scolex
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Proglottid
Testes
Uterus
Vas deferens
Seminal receptacle
Ovary
Yolk gland
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Pork Tapeworm (Taenia solium)
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Taenia
saginata
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Echinococcus granulosus
• A tapeworm that
causes a potentially
fatal parasitic disease
called hydatid
disease.
• Herbivores, and
sometimes humans,
become the
intermediate hosts
after ingesting eggs
on vegetation.
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Echinococcus granulosus
• The eggs then hatch into
embryos that lodge in
tissues and grow into
huge cysts containing
thousands of tapeworm
larvae.
• When the cysts finally
cause the host to die or
become easy prey, they
are ingested by the
scavenger/predator and
become adults in their
intestinal tracts.
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The End
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