P HYLUM P LATYHELMINTHES (Flatworms)

1. PHYLUM PLATYHELMINTHES(Flatworms) Planaria Flukes Tapeworms FACT: Longest human tapeworm = 12 meters long Longest tapeworm = 40 meters long

2. PLATYHELMINTHES • platy • Greek for “flat” • helminthes • Greek for “worm” • moving “up” the ladder of evolution • more complex than Porifera and Cnidaria • however, through evolution has simplified • Three Classes • Class Turbellaria – example planaria • Class Trematoda – example flukes • Class Cestodae – example tapeworms

3. PLATYHELMITHES • MULTICELLULAR • cells are specialized and organized into tissues and organs • have sensory organs concentrated at anterior (head) end = cephalization • GERM LAYERS • have endoderm , ectoderm andmesoderm • Endoderm – forms inner gut • Ectoderm – forms outer epidermis • Mesoderm - forms muscle tissue and reproductive, and excretory organs

4. PLATYHELMINTHES • MOVEMENT • Some larval stages move using cilia • Adults move using muscle contractions • http://www.youtube.com/watch?v=axBaCD4wYXE&feature=related

5. PLATYHELMINTHES • REPRODUCTION • Asexual – fragmentation or budding • Sexual - monoecious, produce both egg and sperm • - a true hermaphrodite with both male and female • reproductive organs • sexual • asexual

6. PLATYHELMINTHES • BODY ORGANIZATION • mesoderm but no body cavity – acoelomate • bilateral symmetry • non-segmented • have tissues and organs • cephalized = concentration of sensory organs at anterior end

7. PLATYHELMINTHES • BODY SYSTEMS • REPRODUCTIVE SYSTEM - a true system • a true hermaphrodite • proglottids – repeating reproductive structures • proglottid

8. PLATYHELMINTHES • BODY SYSTEMS • DIGESTIVE SYSTEM – a simple system • feed on small animals and larger dead animals • mouth is midway along the ventral side (mouth = anus) • muscular pharynx pushes food into gastrovascular cavity • circulates nutrients and oxygen http://www.youtube.com/watch?v=MeJQdbMge84

9. PLATYHELMINTHES • BODY SYSTEMS • CIRCULATORY and RESPIRATORY SYSTEMS – not a true system • part of the gastrovascular cavity • nutrients and gasses diffuse directly across the thin cell layers

10. PLATYHELMINTHES • BODY SYSTEMS • EXCRETORY SYSTEM – a rudimentary system • Two networks of tubes • Attached to tubes are flame cells • work similar to a kidney • cilia that cause excess body fluid to move along excretory tubes and eventually out of body

11. PLATYHELMINTHES • BODY SYSTEMS • MUSCULAR SYSTEM – a true system • controlled by longitudinal, circular, and oblique layers of muscle • sometime assisted by secreting a layer of mucus

12. PLATYHELMINTHES • BODY SYSTEMS • SKELETAL SYSTEM – NONE • NERVOUS SYSTEM – a true system

13. Taxonomy • Class Turbellaria e.g. Planaria • Free living • Incomplete gut • No suckers or hooks • Class Trematoda e.g. Flukes • Parasitic • Incomplete gut • Suckers • Outer cuticle • Class Cestoda e.g. Tapeworms • Parasitic • No gut • Suckers and hooks on a scolex • Body consists of repeating sections called proglottids

14. Fluke (liver, lung, heart, intestine) • Parasitic • Pharynx swallows host’s tissue and body fluids (including blood) • Common intermediate host: raw fish • No need for circulation or respiratory system • Live in tissues supplied by host’s blood • Absorb through gastrovascular cavity • Flame cells • Nerve cords and anterior ganglia • Do not have as specialized nerve cells like Planaria • Hermaphrodites • Complex life cycle with numerous larval stages that infect a number of hosts.

15. Liver Fluke Life Cycle

16. Tapeworm • Parasitic • Specialized for living within a host • Lost most body systems • No digestive, nervous, excretory, muscle systems • Absorb food by diffusion through skin • Has specialized reproduction

17. Tapeworm reproduction • Specialized body sections called Proglottids • Hermaphroditic • Contain both ovaries and testes • Can fertilize their own eggs • Zygotes are passed out of host’s body with feces • Larvae hatch in water and in grass • Eaten by herbivore (intermediate host) – larvae then burrows through wall of intestine and into blood stream • Intermediate host contains tapeworm cysts (bladder worm)– when ingested by final host (e.g. human) cyst hatches out as scolex which then grows proglottids

18. Tapeworm cont’d • Two body regions • Scolex – “head” • No cephalization • Hooks and suckers used to attach to inside wall of intestine • Proglottids • Body segments for reproduction

19. Mammal intestine tapeworm (Taenia taeniformis) • This adult tapeworm has a head (scolex) with suckers and / or hooks that anchor to the intestinal wall of the host. • While the tapeworm grows in the host's intestine, body segments called proglottids bud off its head and neck regions. • This species occurs most often in rabbits, cats and rodents, but sometimes humans, causing diarrhea, weight loss and abdominal discomfort. Adult tapeworms may grow 5-10 meters in length.

20. Tapeworm life cycle

21. MMmmm Tapeworms • As part of a University of Salford experiment to develop a diagnostic test for beef tapeworm, biologist Mike Leahy volunteered to grow this gruesome parasite inside his own gut. • Mike swallowed the immature tapeworm cyst with a glass of red wine and the worm started to grow at an initial rate of four centimetres a week. • Twelve weeks later he had to call a halt to the unusual experiment because he was getting married! • After a dose of anti-worm pill Mike passed out an intact tapeworm three metres long.