1. Unit 5.1 Phylum Platyhelminthes

2. Phylum Platyhelminthes
Flat worms
Triploblastic – three primary germ layers
Acoelomate – no body cavity
Bilateral symmetry
Hermaphroditic
Monoecious – Having both sperm and egg producing parts
One opening for digestive system – located ventrally. Food is eaten and excreted through the same tube.

3. Phylum Platyhelminthes
Paired lateral nerve cords & cerebral ganglion – very simple
Flame cells – specialized “kidney” cells
No specialized circulatory or respiratory systems – must be flat so nutrients & oxygen can diffuse throughout the body

4. Echinodermata Uniramia Chelicerata Chordata Crustacea Protochordates
Lophophorates
Crustacea
Protochordates
Arthropoda
Annelida
Hemichordata
Mollusca
Other
pseudocoelomates
Nemertea
Platyhelminthes
Nematoda
Ctenophora
Cnidaria
Mesozoa
Placozoa
Sarcomastigophora
Ciliophora
Porifera
Apicomplexa
Microspora
Myxozoa

5. Acoelomate Ectoderm Mesoderm Endoderm
Coelom – A fluid filled space that is completely
surrounded by mesoderm

6. Fig. 14.1

7. Acoelomate Phylum Platyhelminthes: Class Turbellaria
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Phylum Platyhelminthes: Class Turbellaria
Acoelomate

8. Pseudocoelomate Ectoderm Mesoderm Endoderm
Coelom – A fluid filled space that is completely
surrounded by mesoderm

9. Coelomate Ectoderm Mesoderm Endoderm
Coelom – A fluid filled space that is completely
surrounded by mesoderm

10. Nervous System Lateral nerve cord Cerebral ganglion Connectives
Eye spot
Auricle

11. Brain
Auricle
Cerebral
ganglion
Paired
nerve cords

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Excretory System

13. Fig. 14.6a

14. Fig. 14.6b

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Turbellaria

17. Class Turbellaria Eye spots – detect simple light gradients.
Ciliated skin surface secretes mucous and aids in movement.
May be aquatic or terrestrial. Terrestrial species are all nocturnal.
Most are free-living – not parasites but predators/scavengers.

18. Class Turbellaria
Planarians have the ability to regenerate new body parts or to generate an entirely new organism from pieces of themselves.

19. Fig. 14.2

20. Class Trematoda Flukes Parasites Holdfast devices Complex life cycle
Most possess these
Complex life cycle
Intermediate host
Animal with juvenile stage
Definitive host
Animal with adult stage

21. Fig. 14.7

22. Clonorchis sinensis Oral sucker Intestine Uterus Yolk gland Ovary
Testes
Ovary
Seminal recepticle

24. Clonorchis sinensis Chinese liver fluke 50 million people infected.
Cirrhosis of liver – liver tissue is replaced by non-functioning scar tissue that impairs overall liver function
Diarrhea
Edema – fluid beneath the skin.
Severe gut pain.

25. Fig

26. Fascioloa hepatica Sheep liver fluke Sheep, cattle and man
Weight loss
Eat vegetation contaminated with metacercariae – small capsules that house the intermediate stage of the fluke.

27. Life Cycle of the Sheep Liver Fluke
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Life Cycle of the Sheep Liver Fluke

28. Fasciolopsis buski Intestinal fluke 10 million people Man and pigs
Hemorrhage and abscesses of small intestine

30. Paragonimus westermani
Lung fluke
Carnivores, pigs, rodents and man
May be fatal

33. Schistosoma Blood flukes – parasitize mesenteric blood vessels.
200 million people infected.
1 million deaths/year.
Second most deadly parasite behind malaria.
Males wrap around females & they exist in pairs throughout adult lives.

34. Life Cycle of a Schistosome Fluke
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Life Cycle of a Schistosome Fluke
Eggs are expelled in urine or feces to fresh water where
the larvae pass through an intermediate stage involving a snail
host and then enter through the skin of a passing human host.

35. Schistosoma
The eggs all have a hook that tears bodily tissues throughout the human host causing more damage as they are passed.
Larvae have a forked tail that assist them in borrowing through human skin.

36. Schistosoma

37. Swimmers Itch – Related to Blood Fluke

38. Swimmers Itch Need avian hosts to complete their life cycle.
Humans are “accidentally” infected and develop a rash for around a week.
Sores develop around burrowing sites but the larvae die within a few hours of entering the skin

39. Class Cestoidea Tapeworms
No digestive system – suck in pre-digested nutrients from the intestines of the host that are directly utilized in metabolic processes.
Can grow up to 100 feet long. Human tapeworms may reach 60 feet in length.

40. Class Cestoidea
The scolex, or head, is equipped with suckers designed to anchor the worm to the intestinal wall and to suck in nutrients.
The proglottids are hermaphroditic segments, each able to detach from the body and produce eggs.

41. Class Cestoidea
Infections are usually asymptomatic other than lethargy and/or dull abdominal pain.
The lethargy is due to a lack of nutrients caused by the tapeworms’ feeding. This leads to weight loss.
People may purposefully infect themselves with tapeworms to lose weight.

42. Scolex

43. Proglottid Testes Uterus Vas deferens Seminal receptacle Ovary
Yolk gland

44. Pork Tapeworm (Taenia solium)
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Pork Tapeworm (Taenia solium)

45. Taenia saginata

46. Echinococcus granulosus
A tapeworm that causes a potentially fatal parasitic disease called hydatid disease.
Herbivores, and sometimes humans, become the intermediate hosts after ingesting eggs on vegetation.

47. Echinococcus granulosus
The eggs then hatch into embryos that lodge in tissues and grow into huge cysts containing thousands of tapeworm larvae.
When the cysts finally cause the host to die or become easy prey, they are ingested by the scavenger/predator and become adults in their intestinal tracts.

49. The End