1. Phylum Platyhelminthes 4 principal types of flatworms
divided into 4 taxonomic Groups
Class Turbellaria
>3,000 free-living spp
some commensal
a few parasitic forms
Aquatic, few on land
Body architecture adapted to a free-living lifestyle

2. Class Monogenea ~ 400 spp mostly ectoparasites of fish, amphibians. P
Feed on blood, mucus..
Anterior and posterior ends for clinging, but life cycle remains simple, with a single free living larval stage P
haptors A

3. Class Trematoda: flukes
> 6000 spp of endoparasites (liver, lungs, blood, muscles)
Body and life cycle adapted to parasitic existence.
Ventral sucker
Oral sucker

4. Class Cestoda: tapeworms
> spp of endoparsites, almost all intestinal parasites with highly specialized body and life cycle.
scolex
9 ft tapeworm from human host
Largest in sperm whale was over 30 meters long

5. There is currently a debate between scientists about the position of comb jellies and sponges in the tree of animal life. What is the basis for this debate, and why is it important to our understanding of the evolution of several important animal organ systems?

6. Characteristics of the Phylum
Bilateral symmetry
Triploblastic

7. Characteristics of the Phylum
Bilaterally symmetry
Triploblastic
Unsegmented
Acoelomate

8. Characteristics of the Phylum
Bilaterally symmetry
Triploblastic
Unsegmented
Acoelomate
Organ Systems
Digestive System

9. Characteristics of the Phylum
Bilaterally symmetrical
Triploblastic
Unsegmented
Acoelomate
Organ Systems
Excretory System
W/ Ultrafiltration and selective absorption

10. Characteristics of the Phylum
Bilaterally symmetrical
Triploblastic
Unsegmented
Acoelomate
Organ Systems
Complex reprod. System
Regenerative capacities

11. Most Widely Accepted Phylogeny of the Major Flatworm Classes
Cestoda
(endoparasitic)
Monogenea
(ectoparasitic)
Neodermata
Trematoda
(endoparasitic)
Turbellaria
-- Parasitic groups considered to be monophyletic and constitute a grouping known as the Neodermata
Synapomorphies: new skin, obligate parasitism,
protonephridia from two cells
No synapomorphies for the phylum; thought to be polyphyletic?
Introduce parasites here:
Includes two groups of endoparasites and one ectoparasitic group.
Endoparasism twice or lost?
Synapomorphies of allparasites
Challenges of Endoparasitism

12. Problems Posed by Endoparasitic Existence

13. Problems Posed by Endoparasitic Existence
Reproduce and get embryos out of the host
Contact new, appropriate host and obtain entrance
Locate appropriate environment in the new host
Maintain position in the host, withstand often anaerobic conditions and attack by immune system
Avoid killing the host, at least until reproduction has been completed

14. In all Neodermata, epidermis is shed, and replaced by a syncitial tegument.

15. The body wall is a tegument with extensive
microvillar surface area
Monogenean tegument Cestode tegument

16. Advantages to having
a tegument?

17. Class Cestoidea: primarily the tapeworms
Body in segments called proglottids -formed behind the small head and continue to grow until released
Mouth, digestive system lacking
Scolex attachment structure
Tegument highly folded with microvillar extensions
Hermaphrodites
Intestinal
Parasites, commonly on vertebrates

18. Reproduction is primarily sexual
Relatively simple
Passive dispersal
Reproduction is primarily sexual
oncosphere

19. Cystecercoids (especially from the pork tapeworm Taenia solium) can accidentally end up in other parts of a body, especially in accidental hosts such as humans when they ingest eggs

20. Reproduction is primarily sexual
Relatively simple
Passive dispersal
Reproduction is primarily sexual
oncosphere

21. oncosphere

22. Hydatosis of the Liver

23. Class Trematoda: all endoparasites in blood, liver, gut
distinguished by presence of ventral sucker
(acetabulum), mouth and highly branched G-V Cavity
Usually 2 intermediate hosts, at least one being a
mollusc; the final host is a vertebrate

24. Class Trematoda: Ex. Chinese Liver Fluke Common in China, Korea
Japan, where practice
of eating uncooked
fish is common
Adults live in the liver
and bile passages
Clonorchis sinensis

25. Class Trematoda: A snail is usually the intermediate Host
Schistosoma mansoni
A snail
is usually
the
intermediate
Host

27. Class Trematoda: Eggs pass through blood vessel into gut, and out….
Or they lodge in nervous tissue, muscles, other organs, causing excrutiating pain &tissue damage.
Schistosome life cycles are unusual
in several ways
-- One intermediate host
-- Have Separate Sexes!
-- Adults live within blood
vessels, feed on blood
Schistosome Egg and spine

28. Class Trematoda: Schistosome life cycles are unusual in several ways
Separate sexes: dioecious
Picture of the
Happy couple

29. Of 200 million infected approximately 120 million show symptoms
Of 200 million infected approximately 120 million show symptoms. The mortality rate is about 2.5% but more frequent in children (5 million deaths, 200K in Sub-Saharan Africa alone)

30. 3 species mainly
invade humans
S. japonicum
S. haematobium
S. mansoni

31. General Pathology
S. mansoni, S japonicum
Acute schistosomiasis: fever, nausea, cough etc., and granuloma formation after female begins to lay eggs
Chronic Schistosomiasis: could be years later
intestinal schistosomiasis: granulomatous inflamation around eggs; colonic polyps, especially in Egypt.
hepatosplenic schistosomiasis: inflammation around eggs trapped in liver, leading to fibrosis, cirrhosis
S haematobium:
parasites in the bladder and ureter, can lead to
calcification, cancer….”urinary schistosomiasis”