1. Flatworms, Roundworms, & Rotifers
Chapter 34

2. Phylum Platyhelminthes
Section 34.1

3. General Structure: 3 germ layers – ectoderm, mesoderm, and endoderm
acoelomates
Bilateral symmetry
Anterior and posterior ends
Dorsal and ventral surfaces only
Flat body plan
Flatworms!

4. General Functions:
Exchange oxygen and carbon dioxide directly with the environment to cells by diffusion
No circulatory system or respiratory system needed
Only one opening where food and wastes pass through!
Cephalization

5. Turbellaria - non-parasitic
Classification:
Four Classes:
Turbellaria - non-parasitic
Trematoda- parasitic
Monogenea - parasitic
Cestoda –parasitic

6. 1. Class Turbellaria: 4,500 species Mostly marine
Swim in wavelike motion
Glide over solid surfaces on layer of mucus
Example: Planarian Dugesia
freshwater
Video

7. Planarian Body Plan:

8. Planarian Organ Systems:
Digestive System:
Scavengers & predators
Decaying plants & animal matter
Prey on smaller organism
Pharynx – throat that extends to the middle of body
video
Pharynx

9. Planarian Organ Systems:
Excretory System:
Flame Cells – enclosed tufts of cilia that draw excess water together and excretes it through pores
video
Flame Cells

10. Planarian Organ Systems:
Nervous System:
Cerebral ganglia: two clusters of nerve cells at anterior
“Brain”
Can learn
Eyespots: sense direction and intensity of light
Other senses: touch, water currents, chemicals

11. Planarian Organ Systems:
Reproductive System:
Sexual:
Hermaphrodites
Eggs laid in protective capsule
Hatch in 2-3 weeks
Asexual:
Regeneration

12. 2. Class Trematoda & 3. Class Monogenea:
Both are parasitic flukes
Leaf-shaped flatworms
Endoparasites:
Live in blood, intestines, lungs, liver, etc.
Ectoparasites:
Live on external surfaces of aquatic hosts

13. Structure of Flukes Anterior & ventral suckers for attachment to host
Nervous system like planarian
Except NO eyespots
Tegument – outer layer that protects from host’s immune and digestive system

14. Liver fluke

15. Reproduction of flukes:
Most are hermaphroditic
May release 10,000+ eggs at a time!
Complicated life cycle (p. 692)

16. Life Cycle:
Primary host: adult parasite gets nourishment from this host
Sexual reproduction
Intermediate host: larvae derive nourishment here
Asexual reproduction

17. Fluke Diseases in Humans
Swimmer’s itch: minor skin irritation and swelling
Small brown fluke in lakes (in Ohio)
Dies within skin because humans are not ideal hosts

18. Swimmer’s itch

19. Schistomiasis (blood fluke):
disease that causes tissue damage, bleeding, tissue decay and possible death
Lungs, intestine, bladder, & liver
200 million people affected worldwide
Human- Primary host
Snail- Secondary or
Intermediate host
Animation!

20. WHO Info.

21. 4. Class Cestoda 5,000 species of tapeworms
Can live in intestines of most vertebrates
Enter through undercooked food with eggs or larvae
Symptoms of infection:
Digestive problems
Weight loss
Lack of energy
anemia

22. Structure: Tegument to protect from host
Also absorbs nutrients from host
Scolex: knob-shaped organ with hooks and suckers to attach to host
Proglottids: body sections after a short neck
Up to 2,000 per tapeworm!

23. Reproduction: Hermaphrodites Each proglottid has ovaries and testes
Filled with 100,000+ eggs each!
Eggs fertilized by sperm of different proglottid

24. Life Cycle:
Cysts: dormant larvae surrounded by protective covering in animal muscle

25. Phylum Nematoda & Rotifera
Section 34.2

26. General Characteristics:
Bilateral symmetry
Fluid filled body cavity
pseudocoelomate
Holds internal organs
Stores sperm & eggs
Supports body
Structure that muscles can contract against

27. Phylum Nematoda Roundworms 1mm to 4ft Digestive tract with 2 openings
Long, slender bodies that taper at both ends
1mm to 4ft
Digestive tract with 2 openings
Anterior – mouth
Posterior – anus
One directional movement

28. Continued… Most have separate sexes Cuticle – protective covering
Free-living on land, salt and freshwater
15,000 species known
150 species parasitic to plants and animals
Humans are host to 50 species!

29. Ascaris: Roundworm parasite that lives in intestine
Pigs, horses, & humans
Can totally block host’s intestine
Up to a foot in length
Female produces 200,000 eggs/day

30. Video

31. Life Cycle: Eggs leave with feces and enter soil
Enter humans with contaminated
food and water
Larvae enter intestines and
move to blood stream, then
lungs, coughed up and swallowed back
to intestines where they mate and reproduce

32. Hookworms: Another intestinal parasite
Mouth has cutting plates that clamp onto intestine wall
Feed on host’s blood which may lead to anemia
May cause slow mental and physical development in children
Affects 1 billion people in tropical and subtropical regions

33. Hookworm
Enter host by boring through the feet
Video

34. Life Cycle: Eggs leave with feces Larvae develop in soil
Enter host’s feet
Hitch a ride with blood to the lungs
Coughed up and swallowed to intestines where adult develop

35. Trichinella: Video Infect humans and pigs
Adults embed in walls of intestine
Larvae travel via blood to muscles
Form cysts
Humans get it from eating undercooked pork
Causes disease trichinosis
Muscle pain & stiffness
Can cause death
Video

36. Pinworm – most common in U.S.
Live and mate in lower intestine
Female crawls out at night and lays eggs around anus
Person scratches during sleep and spreads eggs to everything touched
Eggs ingested and hatch

37. Pinworm

38. Filarial worms – 250 million people infected in tropics
Found in lymphatic system (collects excess fluid from blood vessels)
Can cause elephantiasis
Swollen limbs, skin hardens & thickens
Can cause heartworm in dogs and cats
Spread by mosquitoes

39. Phylum Rotifera Most are transparent (see-through)
Free-living in freshwater
100 to 50 micrometers
No water = dry up and look like grains of sand; when water is present again they go back to normal
Cool adaptation!

40. Rotifer Structures: Cilia – sweep food into mouth
Mastax – breaks down food
Stomach
Intestine – absorbs nutrients
Cloaca – digestive, reproductive, and excretory systems empty here
Universal hole
Flame cells – pull excess water together
Anus – hole to the outside

41. Body Parts: video

42. Have cerebral ganglia and eyespots Reproduction by:
Parthenogenesis – unfertilized eggs become adult females