1. Phylum Platyhelminthes
Flatworms
Monogenian
Flukes
Tapeworms

2. Phylum Platyhelminthes
The phylum consists of four classes
Turbellaria (flatworm)
Trematoda (fluke)
Cestoda (tapeworm)
Monogenian

3. 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

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

5. Phylum Platyhelminthes
Taxonomic Summary
Phylum Platyhelminthes (Flatworms)
Class Turbellaria
Class Cestoda
Class Trematoda
Class Monogeneans
Phylum Platyhelminthes

6. Phylum Platyhelminthes
Class Turbellaria
Most are free–living, benthic, tiny and inconspicuous
Primarily marine and freshwater, many interstitial
4,500 species
Free-living
Flatworm
Phylum Platyhelminthes

7. Flatworm Body Plans
bilateral symmetry
Acoelomate
triploblastic

8. Digestion
Mouth is usually located at the anterior end or mid-body on ventral surface
Some species also have a protrusible pharynx that captures food and transfers it into the mouth
Can be carnivores or scavenge on dead animals and detritus

9. Digestion
Mouth is usually located at the anterior end or mid-body on ventral surface 9 9

10. Feeding Habits
Some species also have a protrusible pharynx that captures food and transfers it into the mouth
Can be carnivores or scavenge on dead animals and detritus

11. Feeding Habits

12. Excretion Excretory system Contains flame bulbs 12
Flatworms have the first true excretory system. Special cells called flame cells are located near the head of the animal. These cells have large flagella in them that wave, creating a low pressure area. The flame cells are connected to the rest of the body by a pair of lateral excretory ducts. Wastes are pulled from body cells into the ducts. Once in the ducts, the wastes move toward the flame cells. Once the wastes get to the flame cells they are released through a dorsal excretory pore. 12 12

13. Nervous System
Posses several nerve cords with a centralized ganglia (brain)

14. 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

15. Mating & Reproduction
Chemosensory to find mate
Hermaphroditic

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

17. Camouflage
flatworm
nudibranch

18. Toxins Staurosporine Tetrodoxin
< Staurosporine and its derivatives belong to a group of organic chemical compounds called indolocarbazole alkaloids. They are known as potent antibiotics and strong insecticides.  Two of these compounds, 3-hydroxy-3'-demethoxy-3'-hydroxystaurosporine and 11-hydroxy-4'-N-demethylstaurosporine, were isolated from the marine polyclad flatworm Pseudoceros concineus and his favored food, the ascidian Eudistoma toealensis (Tunicata). Both animals are brightly coloured and show a high abundance in the mangroves of Truk Lagoon, Micronesia. Feeding experiments with tropical reef fish showed that the crude extract from the ascidian was highly deterrent towards fish, suggesting that staurosporine acts as a highly potent chemical defence substance against predators (Schupp et al., 1997). It is not known yet, wether the flatworm's metabolism is able to produce staurosporine by itself. It is more likely that the actual source of the toxic compound is the ascidian. After feeding on the poisonous tunicate the polyclad flatworm becomes unpalatable because it stores the toxin in his own tissues. 
< Tetrodotoxin is a non-protein organic compound (aminoperhydroquinazoline) and one of the strongest paralytic toxins known today. It is a very specific blocker of voltage-gated Sodium (Na+) channels, large integral membrane proteins that form pores through the plasma membrane of neuronal cells that allow Na+ ions to cross. Pores (=gates) open and close in response to a variety of stimuli such as changes in membrane potential or the presence of certain chemicals outside or inside the cell. Their proper functioning is absolutely essential for neuronal action potentials. Tetrododoxin, however, blocks these channels irreversibly leading to rapid paralysis through interference with neuromuscular conduction.

19. Class Turbellaria
Hawaiian Flatworms

20. Pseudoceros dimidiatus
Hawaiian Flatworms
Pseudoceros cf. rubroanus
Pseudoceros ferrugineus
Planocera cf. oligoglena
Pseudoceros dimidiatus
Pseudobiceros sp.
Class Turbellaria

21. Class Cestoda (Tapeworms)
Defining characteristics
Scolex
Proglottids
Phylum Platyhelminthes

22. 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

23. Problems of a parasitic existence
Reproduce within the definitive host
Get fertilized eggs out of the host
Contact a new and appropriate host
Obtain entrance into the host
Locate the appropriate environment within the host
Maintain position within the host
Withstand an often anaerobic environment
Avoid digestion or attack by the hosts immune system
Avoid killing the host, at least until reproduction is completed
Phylum Platyhelminthes

24. 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

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

26. Trematodes of Concern
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