figure 10.24. class trematoda parasitic flatworms called “flukes” all adult flukes are parasites...
TRANSCRIPT
Class Trematoda 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 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
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)
Important Parasites of Human Chinese Liver Fluke
Common parasite in Asia Over 30 million infected
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 Sheep Liver Fluke
Common in sheep-raising areas 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-me-the-lung-fluke.html
Schistosome Fluke “Schistosomiasis” Common in Africa, S. &
Central America & S.E. Asia Over 200 million infected Decays liver, lungs, spleen
or intestines 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”
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-schistosomiasis-parasite.html
Class Cestoidea
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
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.
Sometimes, dormant, protective cyst is formed in the intermediate host muscles.*** This is why you should never eat incompletely cooked meat!!
Beef Tapeworm 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
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 fluid-filled 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-equipment-usa.com/marine/AUG04/Blue_Flatworm(Cycloporus_sp).html
Blue Flatworm(Cycloporus sp) http://www.scuba-equipment-usa.com/marine/AUG04/Hancock_Flatworm(Pseudobiceros_hancockanus).htmlHancock Flatworm(Pseudobiceros
hancockanus)