Phylum : Platyhelminthes
The Flatworms
Acoelomates
Classes of Platyhelminthes
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Class Turbellaria (e.g., Planaria)
The Flukes
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Class Trematoda (e.g., Fascioloaris,
Clonorchis)
Class Monogenea
Class Cestoda (e.g., Taenia)
General Characteristics
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Free-living or parasitic
Bilaterally symmetrical, and dorsoventrally
flattened
First animals with 3 germ layers - triploblastic
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Ectodermis
Mesodermis
Endodermis
Epidermis has cilia or cuticle
Coelom lacking (acoelomate)
General Characteristics cont.
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Digestive system incomplete
Excretory system – protonephridia
Nervous system – ladder-like
Respiratory, circulatory, and skeletal
system lacking
Most monecious
Some have fragmentation and
regeneration (Asexual)
Figure 14.01
Class Turbellaria
Freeliving Flatworms
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Free-living
Ciliated epidermis
Mouth ventral
Digestive system incomplete
Dugesia w.m.
Eyespots
Auricle
Figure 14.02
Freshwater Flatworm
Figure 14.co
Marine Flatworm
Marine Flatworm
Trematoda and Monogenea
The Flukes
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Endoparasites
Cuticle covering body
Oral sucker surrounds mouth
Ventral sucker used for attachment
Complex life cycles
Clonorchis
Clonorchis
One Intermediate host
Shistosoma – Blood Fuke
Clonorchis – Chinese liver fluke
Two Intermediate hosts
Cestoda
The Tapeworms
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Endoparasites
Body consists of proglottids and scolex
Proglottids snapshots of development
Scolex has structures for attachment
(Hooks, suckers and rostellum)
No digestive system
Figure 14.18
Figure 14.19
Taenia scolex
Mature
Proglottids
Figure 14.20
Taenia – can get to 30+ feet long
Hydatid Cysts of dog tapeworm in human brain
A case of a parasite in the wrong host