Transcript Chapter 10 Pt 2 - s3.amazonaws.com

Figure 10.24
Class Trematoda
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Parasitic flatworms called “flukes”
All adult flukes are parasites of vertebrates
(live in mouth, skin, or gills of host)
Outer body lacks cilia; tegument: has a
layer of glycoproteins that are important in
protection against the host’s immune
system.
Types of Hosts
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Most have complex life that alternates
between asexual and sexual stages
Most require at least 2 different types of
hosts to complete their life cycle (most
complex in all animal kingdom)!!
Primary host: the host in which a parasite
reproduces sexually
Intermediate host: the host in which
asexual reproduction occurs
Adhesive Organs
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Oral sucker: anterior
sucker that surrounds the
mouth (attaches to host
organs)
Acetabulum: below the
oral sucker on the middle
portion of the body
(attaches to host tissue)
Opisthaptor – Extremely strong adhesion
Important Parasites of Human
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Chinese Liver Fluke
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Common parasite in Asia
Over 30 million infected
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Adult lives in bile duct of the liver feeding on epithelial
tissue & blood
Embryonated eggs are released into the common bile
duct
Eggs make their way to intestines to be eliminated in
feces
Snail ingests eggs
Emerges in waters
Enters epidermis of fish that make contact
Human eats raw or poorly cooked meat
Important Parasites of Human
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Sheep Liver Fluke
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Common in sheep-raising areas
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Adult lives in bile duct of the liver feeding on epithelial
tissue & blood
Embryonated eggs are released into the common bile
duct
Eggs make their way to intestines to be eliminated in
feces
Eggs hatch in freshwater and locate proper species of
snail.
Encysts aquatic vegetation
Sheep graze on vegetation & become infected
Humans infected by eating watercress
http://animal.discovery.com/videos/monsters-inside-methe-lung-fluke.html
Schistosome Fluke “Schistosomiasis”
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Common in Africa, S. &
Central America & S.E. Asia
Over 200 million infected
Decays liver, lungs, spleen
or intestines
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Female fluke lays eggs in
intestines or bladder of human.
Egg secretions weaken walls
causing blood vessels to
rupture; eggs leave the body.
If reach freshwater, eggs hatch
into ciliated free-swimming
larvae.
Schistosome Fluke “Schistosomiasis”
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Burrows into aquatic snail tissue further developing.
Leave snail to swim about.
Attach to human skin that comes in contact releasing
tissue-degrading enzymes.
Larvae enter body and migrate to circulatory system.
Cycle begins over.
http://animal.discovery.com/videos/monsters-inside-me-the-schistosomiasisparasite.html
Class Cestoidea
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Tapeworms
Long, flat, parasitic
Live in intestines
Range from 1 mm to 25 cm!!
Lack a mouth & digestive
tract; absorb nutrients across
body wall
Cestoidea
Anterior region is
called a scolex; often
armed with circular
suckers and hooks
called rostellum
Cestoidea
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Extending from the
neck is a series of
individual segments
called proglottids;
contain the sex organs
and eggs.
Each segment is a
reproductive sack and
as it ripens it breaks off
and exits host through
the feces; full of eggs.
Cestoidea
http://animal.discovery.com/videos/monsters-inside-me-pork-tapeworm.html
Sometimes, dormant, protective cyst is formed in the
intermediate host muscles.
*** This is why you should never eat incompletely cooked
meat!!
Beef Tapeworm
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Weight loss, chronic indegestion, diaherrea
Adults live in small intestines
Reach lengths up to 25 meters
About 80,000 eggs per proglottid break free
Eggs develop into six-hooked larva
(oncosphere)
Cattle graze pastures contaminated with
human feces
Ingest oncospheres
Beef Tapeworm
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Cattle’s digestive enzymes free oncospheres.
Larvae bore through intestinal wall into
bloodstream using hooks
Bloodstream carries larvae to skeletal
muscles, where they encyst and form a fluidfilled bladder
Human eats infected, raw or improperly
cooked meat
Scolex attaches to intestinal wall and
tapeworm matures
That is why it is important to cook your
hamburger all the way through. If not you
could end up with a full fledged T. saginata
living inside of you, and they can grow over a
meter long.
This is a scanning electron micrograph of the scolex (i.e., anterior
attachment organ) of Rhinebothrium sp., a tapeworm in the new order
Rhinebothriidea. The scolex is about 900 µm wide. This species, like all
rhinebothriideans, has 4 bothridia on it scolex, each borne on a
muscular stalk. Credit: Claire J. Healy
Additional Pictures
http://www.scuba-equipmentusa.com/marine/AUG04/Blue_Flatworm(Cycl
oporus_sp).html
Blue Flatworm(Cycloporus sp)
http://www.scuba-equipmentusa.com/marine/AUG04/Hancock_Flatworm(
Pseudobiceros_hancockanus).html
Hancock Flatworm(Pseudobiceros
hancockanus)
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http://cas.bellarmine.edu/tietjen/images/platy
helminthes.htm