1. Bilaterate Phyla

2. Phylogeny Review
Common metazoan
ancestor

3. Simple Bilaterian Phyla

4. Platyhelminth Phylogeny

5. Phylum Platyhelminthes
Triploblastic
Bilaterally Symmetric
Aceolomic
Fig. 14.CO

6. Body Cavity Classification

7. Acoelomate Internal Organization
Fig. 14.1

8. Platyhelminthe Taxonomic Characteriestics
Free-living v parasitic
Incomplete gut
No circulatory system
Centralized nervous system
Secretory glands
Excretory organs
Reproductive organs
Innervated musculature
Pseudoceros bifurcus

9. Platyhelminthes Reproduction Modes
Sexual
Monoecious (hermaphroditic)
Free living forms typically cross fertilize
Schistosoma sp of flukes are dioecious
Asexual
Freshwater turbellarian regenerative properties
Intermediate forms of parasitic classes
Sporogomy of encysted miracidium and redia forms

10. Platyhelminthes Taxonomy
Class Turbellaria
Free living planarians & marine flatworms
Class Trematoda
Internal Flukes
Class Monogenea
External Flukes
Class Cestoda
Tapeworms
All Parasitic

11. Class Turbellaria – Planarian
Dugesia sp
Fig. 14.2

12. Movement of Free Living Turbellarians
crawling Dugesia
crawling Bdellura
swimming polyclad

13. Generalized Turbellarian Anatomy
Fig. 14.3

14. Turbellarian Organ Systems
Protonephridia – Flame cells & tube cells
Fig. 14.6a

15. Turbellarian Organ Systems
Fig. 14.6b

16. Orders of Class Turbellaria
Order Tricladida
Order Polycladida
Fig. 14.9

17. Phylum Platyhelminthes Class Turbellaria
Two tiger flatworms (Pseudoceros crozerri) on clump of orange sea squirts (Ecteinascidia turbinata: tunicates) in Bermuda
Photo Copyright © Diane R. Nelson

18. Phlym Platyhelminthes Class Turbellaria, Order Polycladida
Pseudocerus hancockanum
Coral – Tubastrea aurea
Tunicate – Aplidium cratiferum
Fig

19. Phlym Platyhelminthes Class Turbellaria, Order Polycladida
Amphiscolops sp
Fig

20. The flatworm Mesostoma, catching and eating Daphnia
Video Clip

21. Parasitic Life Cycles Hosts Multiple hosts Parasitic adaptations
Single v multiple
Multiple hosts
Definitive
Sexually reproductive stage of parasite
Intermediate
Asexually reproducing stages, larval stages of parasite
Parasitic adaptations
Syncytial tegument
Loss of centralized nervous system
Decreased digestive & excretory systems

22. Class Trematoda - Flukes
Require 2 or more hosts
Definitive host
Where sexually reproducing fluke lives
Intermediate hosts
Intermediate larval & asexual forms encyst

23. Generalize Fluke Body Plan
Gonopore
Fig. 14.7

24. Fluke Hosts Definitive Hosts Intermediate Hosts
Mammals, Reptiles, Birds
Intermediate Hosts
Arthropods
Gastropods
Fish

25. Clonorchis sinensis Life Cycle – Human Liver Fluke
Fig

26. Trematode Stages
Adult – fluke in liver, bile ducts, respiratory tract, blood
Miracidium – ciliated, swimming larvae
Sporocyst – asexually reproductive stage producing redia (within sporocyst)
Redia – 2nd asexual phase producing cercaria
Cercaria – free swimming larval form
Metacercaria – encysted cercaria

27. Clonorchis Stages Adult Fluke mammal Metacercarial cyst fish Redia Egg
water
Cercaria
Sporocyst
snail
water

28. Blood Flukes: Schistosoma japonicum & Schistosoma mansoni
Fig

29. Swimmer’s Itch Encysted metacercaria of avian schistosomes
fluke in water fowl
sporocysts & redia in snail
miracidium
cercaria
fluke in water fowl
miracidium
cercaria
sporocysts & redia in snail

30. Class Monogenea Monogenea – 1 host External flukes
Fish gill, amphibians
No intermediate hosts
Fig

31. Class Cestoda - Tapeworms
Two hosts
Definitive host – carnivore
Intermediate host – herbivore
Adults live in intestine of definitive host
Larval stages encyst in muscle of intermediate host

32. Cestode Body Plan Attach via scolex
Proglottids develop from base of scolex
Proglottids mature reproductively
Proglottids are shed in feces or crawl from anal opening
Fig

33. Taenia saginata Life Cycle - Human/Beef Tapeworm
Fig

34. Taenia solium – Human/Pork Tapeworm

35. Tapeworm Stages Cysticercus Cysticercoid Coenurus Coracidium
Procercoid
Plerocercoid
Hydatid

36. Broad fish Tapeworm Diphyllobothrium latum

37. Tapeworm Lifecycles Human pathogens
FIGURE 86-4 Generalized life cycle of tapeworms. Taenia saginata, T. solium, Diphyllobothrium latum, Dipylidium caninum. Hymenolepsis nana,
Cysticercus larva in cow and pig; procercoid larva in copepod, plerocercoid (sparganum) larva in fish; cysticercoid larva in insect.

38. Cestode Organs
Each proglottid matures as an egg sack
Fig

39. Host Specificity Hydatid Cysts
Encystment of larva in definitive rather than intermediate host
Cysticercosis
Taenia solium and T. saginata
Echinococcus granulosus (dog tapeworm)

40. Hydatid Cysts in Human Heart

41. Hydatid Cysts in Human Brain
Fig