1. Phylum Platyhelminthes
April Adams
Zoology NCHS

2. Phylum Platyhelminthes
Flat worms
Triploblastic= 3 tissue layers
Acoelomate
Bilateral symmetry
Hermaphroditic
1 opening for digestion
Simple nervous and muscular systems
Flame cells
May be free living or parasitic
CEPHALIZATION

3. Acoelomate Digestive cavity is the only inner cavity Ectoderm Mesoderm
Endoderm
Digestive cavity is the only inner cavity

4. Fig. 14.1

5. Acoelomate Phylum Platyhelminthes: Class Turbellaria
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Phylum Platyhelminthes: Class Turbellaria
Acoelomate

6. Other Body Plans: Pseudocoelomate
Ectoderm
Mesoderm
Endoderm
Fluid filled cavity between the endoderm and ectoderm- pseudocoelom
Differs from a true coelom because….
It is not entirely lined with mesoderm tissue
Organs are not suspended or attached to membranes (mesenteries)

7. Other Body Plans: Coelomate
Ectoderm
Mesoderm
Endoderm
Epithelial lined cavity between digestive tract and body wall

9. Flatworm Body Systems
No Circulatory or Respiratory systems- simple diffusion through body wall
Systems Present-
Digestive
Nervous
Excretory
Reproductive

10. Flatworm Body Systems: Digestive
Incomplete-
mouth
pharynx (to swallow food)
intestine(no anus)

11. Nervous System Lateral nerve cord anterior ganglion sensory receptors
transverse nerve cord
Eye spot= detects light

12. Cephalization=“Primitive Brain”
Auricle
Cerebral
ganglion
Paired
nerve cords

13. Excretory System Gets rid of nitrogenous wastes
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Excretory System
Gets rid of nitrogenous wastes
protonephridia- first kidney
Components:
Flame cells
Excretory ducts/tubes
pores

14. Reproductive System Sexual and asexual reproduction
sexual- eggs + sperm
asexual- regeneration
Hermaphrodites-
both male (penis and testis)
and
female organs(vagina and ovary)
Fig. 14.6a

16. Kingdom Animalia Phylum Platyhelminthes Classes:. Turbellaria
Kingdom Animalia Phylum Platyhelminthes Classes: Turbellaria Trematoda Cestoda

17. Class Turbellaria Most free-living Aquatic Eye spots
Regenerate if cut in two
Ex. Planaria

18. Planarians Free-living flatworm bilateral symmetry
Lives in fresh water usually under leaves and rocks
Usually feeds on dead or slow moving organisms

19. Planarian Reproduction
Sexually: hermaphrodites
Asexually: can regenerate missing body parts (called fission)
each Planaria gives and receives sperm
Detaches its tail end and each half regrows the lost parts
What would happen ????

20. Planarians: body structures
Nervous/sensory system: Brain-like structure
Nerve cord: carries impulses down body
Eyespots: sense light and dark
Sensory pits: line sides of head to aid in movement and sensing surroundings
Flame Cells: remove excess water and nitrogenous wastes

21. Planarians: body structures
Digestive/excretory system
Mouth: located in center of ventral side
Pharynx: tube like structure which extends from mouth during feeding; acts like a straw sucking up food and carrying it to body
Food enters mouth and solid wastes exit mouth
eyespot
ganglion
ganglion
Nerve cord
Gastrovascular cavity
Mouth
pharynx
Flame cells
LABEL YOUR PLANARIAN!!!

22. Class Trematoda Parasites Holdfast devices Endoparasites
Complex life cycle- larval stage in one or more hosts
Primary host-juvenile/larva stage-
sexual reproduction
Secondary host- adult stage, asexual reproduction
Ex. Blood and liver flukes

23. Flukes Blood fluke life cycle:
Eggs are released in water from wastes of infected host
Hatch in to swimming larvae in water
Larvae enter a host (like a snail) where they develop & mature
Enter water again and bore into skin of new host (man)
From the blood stream they bore into intestines where they attach and feed on blood

24. Schistosoma
Blood flukes
200 million people
1 million deaths/year

25. Life Cycle of a Schistosome Fluke
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Life Cycle of a Schistosome Fluke

26. Schistosome
Cercaria have forked tail

27. Swimmers Itch

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

29. Clonorchis sinensis Chinese liver fluke 50 million people
Cirrhosis of liver
Diarrhea
Edema
Pain

30. Fig

31. Fascioloa hepatica Sheep liver fluke Sheep, cattle and man
Weight loss
Eat contaminated vegetation

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

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

36. Class Cestoda: “cess pool”
Tape worms
All parasitic
Live in intestines of vertebrates
No digestive system
40 feet long

37. Tapeworm structures Scolex= head
hooks and suckers to aid in attachment to intestine
Proglottids: individual parts of worm
Each one is detachable
Each proglottid may contain up to 100,000 eggs which fall off when full
When released, they exit with the host’s wastes

38. Tapeworm life cycle
Eggs hatch in intestines of intermediate host (pig or cow)
Young worms burrow out of intestine into pig’s muscle tissue forming cysts
Secondary host (man) eats undercooked/raw meat containing worm larvae cysts
Larvae hatch and mature in intestines
Attach to intestines, soak up digested food of host
May enter bloodstream and infect other tissues

39. Scolex

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

41. Pork Tapeworm (Taenia solium)
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Pork Tapeworm (Taenia solium)

42. Taenia saginata

43. Life Cycle of the Broad Fish Tapeworm
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Life Cycle of the Broad Fish Tapeworm
Diphyllobothrium latum
Source: Redrawn From Centers for Disease Control, Atlanta, GA.

44. Dipylidium caninum

45. Echinococcus granulosus
Parasite of dogs
Host
Juveniles in sheep, man and other mammals
Intermediate host
Hydatid cyst

47. Hydatid Cyst
Cysticercus
Juvenile stage

48. Ecinococcus granulosus
Adult stage in dog