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

Phylum Platyhelminthes Class Monogenea Class Cestoidea Class Trematoda Subclass Digenea

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.

Opisthaptor (Haptor) Ciliated larva

Life cycle of Ecto parasitic monogenean

Gyrodactylus sp.

Polystoma nearcticum Life cycle of Endo parasitic monogenean

Polystoma nearcticum

Spadefoot toad

Tadpole of Spadefoot toad

Tadpoles of Spadefoot Toads

Temporal adaptation Spadefoot toads are parasitized by a Monogenean Pseudodiplorchis americanus

Polystoma nearcticum Pseudodiplorchis americanus

Autoinfection

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

Aspidogastrean flukes

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

Life Cycle

Life Cycle First Intermediate Host Mollusk-snail

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

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!

Life Cycle Egg Miracidium Adult Sporocyst Cercaria Metacercaria Redia

Polyembryony Egg Miracidium Adult Sporocyst Cercaria Metacercaria Redia

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

Egg Miracidium Sporocyst Sporocyst Redia Redia Cercaria Many Metacercaria Many Adults

Life Cycles Basic Pathway Lots of variation