1. Phylum Platyhelminthes

2. General Characterisitics
Bilateral symmetry
Acoelomate
Triploblastic
Dorsoventrally Flattened
Un-segmented bodies
Cephalization (has a head)

3. Actual organ systems present
Characteristics Cont.
20,000 species
Actual organ systems present
Nervous, Digestive, Excretory

4. Taxonomy
3 Classes
Class Turbellaria
Class Trematoda
Class Cestoidea

5. Class Turbellaria Planarians
Free-living bottom-dwellers in aquatic environments
few terrestrial species in the tropics
3,000+ species
Vary widely in color, size, and shape
Terrestrial ones can be up to 60cm

7. Body Description 3 Layers Ectoderm Mesoderm Endoderm
Acoelomate- have a solid mass of mesoderm cells between the ecto- and endo- derms

8. Acoelomate Design

9. Locomotion
As bottom dwellers the flat worms glide over the substrate (ground)
Use cilia and muscular contractions
Lay down a sheet of mucous as they travel (like slugs)

10. Body Systems Digestive- can be simple or complex
Pharynx: muscular ingestion organ
Some digestion takes place outside the body
Enzymes secreted on food particles; helps to break them down so the pharynx can swallow them easier.

11. Digestive System

12. Body System Con’t Respiratory- have none
gases are exchanged over the epidermis
Circulatory
Protonephredia: fine networks of tubes that run the length of the body and collect waste
Flame cells: bulb-like structures that force waste out of the body through openings called nephridiopores.

13. Excretory System

14. Nervous: detecting and responding to environment
Simple: nerve net w/ Statocysts- sense gravity
Complex: nerve net and two main nerve cords with ladder like connections between
Auricles: chemoreception
Ocelli: eyespots; detect light

15. Nervous System

16. Reproductive:
Most hermaphrodites
Exhibit both sexual and asexual
Asexual- transverse fission
Sexual- mutual sperm transfer

17. Planarian Body Systems

18. Class Trematoda
Parasitic flatworms (called flukes)
1mm to 6cm in size
Most infect internal organs – can be blood or virtually any
other organ

19. Primary host = the host in which a parasite reproduces sexually
Intermediate host = the host in which asexual reproduction occurs

20. Fish Flukes
30 million people infected in Asia
Caused by eating raw or improperly cooked fish
Resides in liver bile ducts

21. Causes fever, weight loss, joint aches, inflammation, hives, weakness, diarrhea, and an enlarged liver.

22. Chinese Liver Fluke

23. More Flukes
Liver Flukes
Live in the liver bile ducts of sheep and humans
Host infected by eating aquatic vegetation (watercress)

24. Schistosomes: blood flukes
Millions infected worldwide
Causes rash, fever, chills, inflammation, liver and spleen enlargement.

25. Schistosoma mansoni - multiple host:
Primary host = human
Intermediate host = snail
Causes Schistosomiasis -in humans; decays lungs liver, spleen, or intestines, occurs in tropical areas with poor sanitation/sewage.

26. Blood Fluke

27. Class Cestoidea
Tapeworms
3,500 species
All are endo-parasites of vertebrates

28. Lack a mouth and digestive tract
Body consists of 3 main parts
scolex: hold fast structure
Strobila: the neck region
Proglottids: reproductive sacs that make up 90 percent of the body

29. Each mature proglottid is a hermaphrodite
Testes produce sperm, fertilize the eggs to produce a zygote
Zygotes are passed out through the feces.

31. Sometimes, a dormant, protective cyst is formed in the intermediate host muscles
****This is why you should never eat incompletely cooked meat.

33. Tapeworm Life cycle

34. Tapeworm Life Cycle