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Figure 10.24

Figure 10.24. 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.

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Figure 10.24

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  1. Figure 10.24

  2. 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.

  3. 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

  4. 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)

  5. Opisthaptor – Extremely strong adhesion

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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

  11. Cestoidea Anterior region is called a scolex; often armed with circular suckers and hooks called rostellum

  12. 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.

  13. Cestoidea • http://animal.discovery.com/videos/monsters-inside-me-pork-tapeworm.html

  14. Sometimes, dormant, protective cyst is formed in the intermediate host muscles.*** This is why you should never eat incompletely cooked meat!!

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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).html Hancock Flatworm(Pseudobiceros hancockanus)

  20. http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm

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