1. Phylum Platyhelminthes
The Flatworms

2. Phylum Platyhelminthes
Examples include:
Planaria
Tapeworms
Flukes
Polyclad flatworms

3. Characteristics Bilateral symmetry Flattened bodies 12,000+ species
1 mm to 10 m
Most aquatic or parasitic
External suckers or hooks

4. More Characteristics No coelom
Digestive tube with mouth, anus, and intestine.
Food in through mouth, undigested food leaves through pharynx

5. Muscles are both longitudinal and circular

6. Classification

7. Class Turbellaria Planaria Polyclad flatworms (marine)
Creeping motion achieved through muscles and cilia
Only class containing free living worms

8. Class Trematoda All parasitic flukes
Infect vertebrates, including humans
Leaflike form
Hooks or suckers
Liver fluke, blood fluke, lung flukes, swimmer’s itch

9. Class Monogenea
Parasitic flukes, primarily on gills or external features of fish
Direct life cycle, with a single host

10. Class Cestoda Tapeworms
Internal parasites of vertebrates, including humans
Holdfast called scolex
1000+ species
Life cycle requires two hosts