1. Phylum Platyhelminthes
Classes:
Flatworms (Turbellaria)
Flukes (Trematoda)
Tapeworms (Cestoda)
Monogeneans
Phylum Platyhelminthes

2. Phylum Platyhelminthes
They are Acoelomates
because they lack body cavity (Coelom).
This gives them a flat body structure (Flat worms)
Phylum Platyhelminthes

3. Phylum Platyhelminthes
Flatworm Body Plans
Exhibit bilateral symmetry, acoelomate, and are triploblastic
Parenchyma tissue
Phylum Platyhelminthes

4. Phylum Platyhelminthes
Taxonomic Summary
Phylum Platyhelminthes

5. Phylum Platyhelminthes

6. Phylum Platyhelminthes
CHARACTERISTICS
BILATERAL SYMMETRY
THREE GERM LAYERS (TRIPLOBLASTIC)
CENTRALIZED NERVOUS SYSTEM
SIMPLE EXCRETORY SYSTEM
COMPLEX REPRODUCTIVE SYSTEM
SIMPLE DIGESTIVE SYSTEM
Phylum Platyhelminthes

7. Phylum Platyhelminthes
Reproduction
Almost all are simultaneous hermaphrodites
Parasitic species (flukes and tapeworms) have complex lifecycles, with various hosts and several different larval stages
Incredible powers of regeneration
Phylum Platyhelminthes

8. Phylum Platyhelminthes
Nervous System
Free-living species usually have a well-developed sensory system
Parasites generally have less elaborate systems.
WHY?
Phylum Platyhelminthes

9. Phylum Platyhelminthes
Class Turbellaria
Most are free–living, tiny and inconspicuous
Primarily marine and freshwater
e.g Planaria
Free-living
Flatworm
Phylum Platyhelminthes

10. Digestion and Excretion
Mouth is usually located at the anterior end or mid-body on ventral surface
Excretory system
Contains flame bulbs known as flame cell.
Phylum Platyhelminthes

11. Phylum Platyhelminthes
Regeneration
Many species posses remarkable powers of regeneration and repair wounds
Phylum Platyhelminthes

12. Turbellarian Lifestyles
Most are benthic
Posses several nerve cords with a centralized ganglia (brain)
Phylum Platyhelminthes

13. Phylum Platyhelminthes
Reproduction
Reproduction occurs with the reciprocal exchange of sperm.
Fertilized eggs are released and usually develop directly into flatworms
Muller's larva
Phylum Platyhelminthes

14. Class Cestoda (Tapeworms)
Defining characteristics
Scolex
Proglottids
All parasitic
E.g Taenia saginatta (beef tapeworm)
Taenia solium
(pork tapeworm)
Phylum Platyhelminthes

15. Phylum Platyhelminthes
Proglottids
Proglottids
Each animal can be 3,000 – 4,000 per animal
Amazing reproductive output
Each may contain several ovaries and 1,000 distinct testes
Phylum Platyhelminthes

16. Phylum Platyhelminthes

17. Class Trematoda (Flukes)
All are external and internal parasites of other animals.
Leech-like bodies with a sucker at each end.
Have a gut and well-developed reproductive system, never segmented.
Blood flukes (Shistosomes),Liver flukes (Fasciola) & Lung flukes (Paragonimus)
Phylum Platyhelminthes

18. Schistosomes (Blood Fluke)
Causes infection known as Schistosomiasis (Formally Bilharziasis)
They are dioecious (Sexes are separted)
Adult males carry females in a gynaecophoric canal.
Phylum Platyhelminthes

19. Phylum Platyhelminthes
Schistosome species
Species
Snail intermediate host
Location in host veins
Type of eggs spine
S. mansoni
Biomphalaria
Large intestine
Lateral spine
S. japonicum
Onchomelenia
Small intestine
Small round knob
S. haematobium
Bulinus
Urinary bladder
Terminal spine
Phylum Platyhelminthes

20. Phylum Platyhelminthes
Trematoda Lifecycles
The lifecycle is complex with up to 4 different hosts and several larval types
Phylum Platyhelminthes

21. Phylum Platyhelminthes
Life Cycle of Blood fluke
(Schistosomes)
Trematodes of Concern
Schistosomiasis
Deadly prominent disease in many regions of the world
Bores into the skin of the definitive host and travels in the circulatory system to the heart the lungs and the kidneys where it feeds and grows
Inflammation is caused by eggs becoming trapped in the hosts tissues
Chinese liver fluke
Lives in the bile duct of humans, cats, and dogs (1-2 cm.)
Goes through two intermediate hosts
Infection occurs from ingestion of raw fish
Phylum Platyhelminthes

22. Liver Fluke (Fasciola)
Causes fascioliasis or liver rot in sheeps and dogs.
Major examples : F. Hepatica & F. Gigantica
Snail intermediate host- Lymnaea
Phylum Platyhelminthes

23. Phylum Platyhelminthes
Life cycle of Liver fluke (Fasciola)
Phylum Platyhelminthes