1. Overview Readings Platyhelminthes
Chapter 13 Introduction (skim to appreciate diversity and morphology)
Chapter 14 Aspidobothrea (skim to appreciate diversity)
Chapter 15 Trematoda Introduction
Chapter 18 Plagiorchiformes
Chapter 17 Echinostomatiformes
Chapter 16 Strigeiformes

2. Phylum Platyhelminthes
Class Monogenea
Class Cestoidea
Class Trematoda
Subclass Digenea

3. Class Monogenea: Most ecto-parasites of fish.
Some endo-parasites of urinary bladder and mouth of amphibians and reptiles.
Body covered by tegument.
Posterior hooks with opisthaptor (haptor).
Direct life cycle with single host.

4. Opisthaptor (Haptor)
Ciliated larva

7. Life cycle of Ecto parasitic monogenean

8. Gyrodactylus sp.

9. Polystoma nearcticum
Life cycle of Endo parasitic monogenean

10. Polystoma nearcticum

12. Spadefoot toad

13. Tadpole of Spadefoot toad

14. Tadpoles of Spadefoot Toads

15. Temporal adaptation Spadefoot toads are parasitized by a Monogenean
Pseudodiplorchis americanus

16. Polystoma nearcticum
Pseudodiplorchis americanus

25. Autoinfection

26. Class Trematoda Digenetic and aspidogastrean flukes: all parasitic.
Body covered by tegument.
Most have complicated life cycles with 2-3 hosts (alternation of generations)

27. Aspidogastrean flukes

31. Host Definitions
Definitive Host: Host in which the parasite reproduces sexually.
Intermediate Host: Host in which the parasite develops, but does not become sexually mature.
multiple intermediate hosts.
First Intermediate Host
Second Intermediate Host

32. Life Cycle

33. Life Cycle
First Intermediate Host
Mollusk-snail

34. Life Cycle First Intermediate Host
Mollusk-snail
Second Intermediate Host (wide range of animals, including mollusks, arthropods, and vertebrates!

35. Life Cycle First Intermediate Host
Mollusk-snail
Second Intermediate Host (wide range of animals, including mollusks, arthropods, and vertebrates!
Definitive Host (in most cases vertebrates)
Reservoir hosts can be both an intermediate host and/or definitive host!

36. Life Cycle
Egg
Miracidium
Adult
Sporocyst
Cercaria
Metacercaria
Redia

37. Polyembryony Egg Miracidium Adult Sporocyst Cercaria Metacercaria
Redia

38. Multiple Sporocyst/Redia Generations
Egg
Miracidium
Adult
Sporocyst
Daughter Sporocyst
Cercaria
Metacercaria
Daughter Redia
Redia

39. Egg
Miracidium
Sporocyst
Sporocyst
Redia
Redia
Cercaria
Many Metacercaria
Many Adults

40. Life Cycles
Basic Pathway
Lots of variation