Phylum : Platyhelminthes The Flatworms Acoelomates

Classes of Platyhelminthes Class Turbellaria (e.g., Planaria) Class Turbellaria (e.g., Planaria) The Flukes The Flukes Class Trematoda (e.g., Fascioloaris, Clonorchis) Class Trematoda (e.g., Fascioloaris, Clonorchis) Class Cestoda (e.g., Taenia) Class Cestoda (e.g., Taenia)

General Characteristics Free-living or parasitic Free-living or parasitic Bilaterally symmetrical, and dorsoventrally flattened Bilaterally symmetrical, and dorsoventrally flattened First animals with 3 germ layers - triploblastic First animals with 3 germ layers - triploblastic Ectodermis Ectodermis Mesodermis Mesodermis Endodermis Endodermis Epidermis has cilia or cuticle Epidermis has cilia or cuticle Coelom lacking (acoelomate) Coelom lacking (acoelomate)

General Characteristics cont. Digestive system incomplete Digestive system incomplete Excretory system – protonephridia Excretory system – protonephridia Nervous system – ladder-like Nervous system – ladder-like Respiratory, circulatory, and skeletal system lacking Respiratory, circulatory, and skeletal system lacking Most monoecious Most monoecious Some have fragmentation and regeneration (Asexual) Some have fragmentation and regeneration (Asexual)

Figure 14.01

Class Turbellaria Freeliving Flatworms Free-living Free-living Ciliated epidermis Ciliated epidermis Mouth ventral Mouth ventral Digestive system incomplete Digestive system incomplete

Dugesia w.m. Eyespots Auricle

Figure Freshwater Flatworm

Marine Flatworms

Marine Flatworm

Trematoda and Monogenea The Flukes Endoparasites Endoparasites Cuticle covering body Cuticle covering body Oral sucker surrounds mouth Oral sucker surrounds mouth Ventral sucker used for attachment Ventral sucker used for attachment Complex life cycles Complex life cycles

Clonorchis

Clonorchis

One Intermediate host Shistosoma – Blood Fuke

Two Intermediate hosts Clonorchis – Chinese liver fluke

Cestoda The Tapeworms Endoparasites Endoparasites Body consists of proglottids and scolex Body consists of proglottids and scolex Proglottids snapshots of development Proglottids snapshots of development Scolex has structures for attachment (Hooks, suckers and rostellum) Scolex has structures for attachment (Hooks, suckers and rostellum) No digestive system No digestive system

Figure 14.18

Figure 14.19

Taenia scolex

Figure Mature Proglottids

Taenia – can get to 30+ feet long

Hydatid Cysts of dog tapeworm in human brain A case of a parasite in the wrong host