1. Unsegmented Worms

2. Flatworms

3. Flatworms Belong to the phylum platyhelminthes. (Plat = flat)
There are three classes:
Turbellaria
Trematoda
Cestoda

4. Characteristics of Flatworms
They are acoelomates (they don’t have body cavities)
They have bilateral symmetry
Show cephalization
Respiration, excretion, and circulation through skin (diffusion)
Single opening to digestive tract (pharynx)

5. Characteristics of Flatworms
Soft, flattened bodies
Have tissues and organ systems
Have 3 germ layers (endoderm, mesoderm, and ectoderm)
Can be free-living or parasitic
Around 20,000 species

6. Characteristics of Flatworms
Sexual reproduction: mutual copulation
Asexual reproduction: fragmentation and regeneration
Have simple “brains” (nerve clusters) with nerve cords that run down body (free-living)
Movement by small muscles and cilia

7. Classification Class Turbellaria Class Trematoda (flukes)
Dugesia (planarian)
Class Trematoda (flukes)
Schistosoma
Class Cestoda (tapeworms) 7

8. Class Turbellaria Spade-shaped head and two eyespots (light detection)
Eat protozoans (scavengers)
Flame cells (protonephridia) remove waste
Are hermaphrodites (have male and female reproductive parts)
Can reproduce by regeneration
Are free-living

11. Class Trematoda Are parasitic flukes
Have suckers on both ends of the body
Most live in internal organs of host
Can live inside or outside of host (endo- or ectoparasites)

12. Class Trematoda Nervous and excretory systems like turbellarians
Hermaphrodites
Have complex life cycles usually involving two hosts

14. Class Trematoda (Flukes)
Schistosomiasis: disease caused by parasitic blood flukes (Schistosoma); infects people in Asia, Africa, and South America causing intestinal bleeding and tissue decay that can result in death

15. Fluke Life-Cycles
The long and complex life-cycle of the fluke can be made easier to
understand through the use of a nonsense mnemonic :
Every - Egg Man - Miracidium (free-living in water) Sees - Sporocyst (in snail) Red - Redia (in snail) Colored - Cercaria (free-living in water/snail) Money - Metacercaria (in 2nd intermediate host) A - Adult

16. Class Cestoda Parasitic Tapeworms Long, ribbon-like bodies
Absorbs nutrients from host
Hermaphrodites
Grow by adding proglottids (body sections): each contains male and female reproductive organs

17. Tapeworm Anatomy
Tegument: tough, non-cellular body covering of parasitic worms
Scolex: anterior end, contains hooks & suckers for attachment to intestine of host

21. Roundworms
Roundworms

22. Roundworms Belong to phylum Nematoda
Pseudocoelomates (fluid filled body cavity)
Slender bodies that taper on both ends
Have mouth and anus (0ne-way)
Can be free-living or parasitic

23. Roundworms Microscopic to a meter in length
Predators, detritivores (eat dead material)
Use diffusion for respiration, circulation, and excretion
Nervous system like flatworms

24. Roundworms Move using muscles and hydrostatic skeleton
Reproduction is sexual w/separate species
25,000 species named; actual # ~500,000

25. Roundworms
Marine, freshwater, and soil dwellers; every climate

26. Trichinosis- a disease from eating infected pork

27. Roundworms & Disease
Trichinosis (Trichinella spiralis) - cysts within the muscles are consumed (undercooked food) -- worm grows in intestine -- forms cysts in the muscles of the new host -- symptom: terrible pain in muscles

28. Cysts in Contaminated Pork

29. Filarial Worms - found in Tropical regions of Asia; also in blood and lymph vessels of birds and mammals (heartworms)
-- usually transmitted by mosquitoes -- causes elephantiasis

30. Ascarid Worms (common roundworm) Ascaris lumbricoides - lives in intestine - eggs are passed out in the feces
Most roundworms infect dogs, but occasionally they find their way into human hosts

31. Hookworms Ancylostoma duodenale:
- burrow into the skin from soil - mature in the intestines --hooks used to attach and suck blood

32. Pinworms live in human intestines (Enterobius vermicularis)

33. Research on C. elegans (free living roundworm)
first organism to have DNA completely sequenced
It is a very simple, free living roundworm

34. Phylum Rotifera Known as rotifers or wheel animals
Transparent, free-swimming microscopic animal
Freshwater & marine
Have a ring of cilia around mouth that rotates like a wheel to bring in food
Feed on unicellular algae, bacteria, & protozoa

35. Rotifers
Have a muscular organ called the mastax behind the pharynx to chop food
Nervous system composed of anterior ganglia & 2 long nerve cords
Show cephalization (head end)
Have 2 anterior, light-sensitive eyespots

36. Rotifer Anatomy