Worms and Mollusks

1. Worms and Mollusks Chapter 27:

2. 3 Phylums of Worms 1. Flatworms (phylum Platyhelminthes) Turbellaria (free-living)Trematoda (flukes), Cestoda (tape worms) 2. Round Worms (phylum Nematoda)Trichinella (trichinosis) filarial worms (elephantiasis) Ascaris and hookworms 3. Segmented Worms (phylum Annelida)Oligochaeta (earthworms) Hyrudinea (leeches) Polychaeta (sandworms, bloodworms)

3. Classes of Mollusca Phylum belly-footed (class Gastropoda) “gastro means belly & pod means foot” snails and slugs 2. double-shelled (class Bivalvia) “bi means 2 & valve means shell” clams,mussels, oysters and scallops 3. head-footed (class Cephalopoda) “cephalo means head & pod means foot” octopus, squid, cuddlefish, nautilus

4. “Coelum - fluid filled body cavity line with tissue from mesoderm” “No Coelum” “False Coelum” “True Coelum”

5. FLATWORMS

6. Flatworms Phylum Platyhelminthes Soft, flattened animals with cephalization and bilateral symmetry Acoelomates: 3 germ layers with no true body cavity (coelom) Most are parasitic Terms: pharynx, flame cells, ganglia, hermaphodite Sexual and asexual reproduction Examples: flukes, planaria, tapeworms

7. Flatworms • Acoelomate: flatworms are without a coelom • Coelom: fluid-filled body cavity lined with mesoderm • The digestive cavity is the only body cavity

8. Platyhelminthes Feeding • Free-living flatworms • Carnivores that feed on tiny aquatic animals • Scavengers that feed on recently dead animals • Parasitic flatworms • Feed on blood, tissue fluids, or pieces of cells within a host’s body (Example: tapeworm)

9. Respiration, Circulation, & Excretion in Platyhelminthes • Rely on diffusion • Flame cells: remove excess water and metabolic wastes from the body

10. Platyhelminthes Response • Ganglia: group of nerve cells that controls the nervous system; in the head region • Eyespot

12. Platyhelminthes Movement • Cilia • Muscle cells • Flap to swim

13. Reproduction: Sexually and Asexually in Platyhelminthes Free-living • Sexually: hermaphrodites during sexual reproduction, two worms join in a pair, delivering sperm to each other • Asexually: fission

14. Reproduction: Sexually and Asexually in Platyhelminthes Parasitic • A complex life cycle including both sexual and asexual reproduction

15. Groups of Flatworms: Platyhelminthes • Turbellarians - free-living; most live in marine or fresh water (class Terbellaria) • Flukes - parasitic; infect the internal organs of their host (class Trematoda) • Tapeworms - Long, flat, parasitic; adapted to life inside the intestines of their host (class Cestoda)

16. Free living Flatworms Most live in freshwater or marine environments Bottom dwellers living in sand or mud Most are carnivores or detritus Example: Planarians Groups of Flatworms: PlatyhelminthesClass: Turbellarians

21. Parasitic Flatworms Most flukes infect the internal organs of their host Some are external parasites that live on the skin, mouth, gills of their host Many have complicated life cycles that involve two or more animal hosts They are usually less than a centimeter long They cause serious pain to millions of humans and animals The most destructive live in the tropics. Groups of Flatworms: PlatyhelminthesClass: Trematoda (Flukes)

22. Liver Fluke Life Cycle

23. Flukes of the genus Schistosoma infect about 200 million people per year The Schistosoma fluke causes schistosomiasis in humans A serious disease in which the eggs clog blood vessels which can cause swelling and tissue decay in the lungs, liver, spleen, or intestines Groups of Flatworms: Platyhelminthes Class: Trematoda (Flukes)

24. Blood Flukes

25. Larvae enter humans through skin Reproduce sexually in blood vessels of intestines Release eggs into water Larvae enter snails and reproduce asexually Burrow out and infect humans again More prevalent with no sewage treatment Groups of Flatworms: Platyhelminthes Life Cycle of Schistosoma

26. Blood Fluke Life Cycle

27. Parasitic worms Adapted to live inside the intestines of their hosts Food is digested directly through the body walls Rarely kill but cause weakness & weight loss Groups of Flatworms: PlatyhelminthesClass: Cestoda (tapeworms)

28. Structure of a tapeworm Scolex Structure that contains suckers or hooks Groups of Flatworms: PlatyhelminthesClass: Cestoda (tapeworms)

29. Proglottids Segments that make up most of the worms body Proglottids contain male and female reproductive parts They can contain as many as 100,000 eggs. They can produce as many as half a billion eggs in a year Groups of Flatworms: PlatyhelminthesClass: Cestoda (tapeworms)

30. Tapeworm Life Cycle

31. Taenia saginata, the Beef Tapeworm Groups of Flatworms: PlatyhelminthesClass: Cestoda (tapeworms)

32. ROUNDWORMS

33. Roundworms Phylum Nematoda No segments Many free-living, some Parasitic Pseudocoelomate: 3 germ layers with false cavity(coelom) Digestive system with two openings: mouth and anus Inhabit the soil, salt flats, aquatic sediments and water from polar regions to the tropics Hookworms, trichinella, ascaris • “A rotting apple may contain 100,000 nematodes!”

34. Roundworms

35. Nematode Feeding Carnivores that use grasping mouth parts and spines Free-living roundworms

36. Respiration, Circulation, & Excretion in Nematodes • Exchange gases and excrete metabolic waste through their body walls • No internal transport system • They rely on diffusion to carry nutrients and waste throughout their bodies

37. Nematode Response • Simple nervous systems, consisting of several ganglia • Run from the head to the tail • Nerves transmit sensory information and control movement

38. Nematode Movement • Hydrostatic skeleton • Aquatic roundworms move like snakes • Soil-dwelling roundworms push their way through by thrashing around

39. Nematode Reproduction • Sexually • Separate males and females • Internal fertilization • Male deposits sperm inside the female’s reproductive tract • Parasitic roundworms have complex life cycles involving two or three different hosts or organs within a single host

40. Nematode Reproduction

41. Roundworms and Human Disease Trichinosis-causing worms • Adult worms live and mate in the intestines of their host (humans, pigs and other mammals) Filarial worms • Found primarily in tropical regions of Asia, threadlike worms that live in the blood and lymph vessels of birds and mammals, including humans, transmitted by biting insects, causes elephantiasis

42. Roundworms and Human Disease Ascarid worms • Serious parasite of humans and many other vertebrates, causes malnutrition; spread by eating vegetables or food that are not washed properly Hookworms • Hatch outside the body of the host and develop in the soil, can enter a barefoot and travel through the bloodstream to the intestines

43. Roundworms Causing Human Disease:Trichinosis - Causing Worms Trichinosis is a terrible disease caused by the roundworm Trichinella Adult worms live and mate in the intestines of their hosts which include: Humans, pigs, and other animals Warning… Very Graphic Images! (next 11 slides)

44. Roundworms Causing Human Disease: Trichinella Worm - Trichinosis Humans get Trichinosis byeating raw or incompletely cooked pork.

45. Roundworms Causing Human Disease: Filarial Worms Found primarily in tropical regions of Asia Threadlike worms live in blood and lymph vessels of birds and mammals…including humans Transmitted through bitting insects especially mosquitos Large numbers of filarial worms may block the passage of fluids within the lymph vessels This causes what is known as elephantiasis

46. Roundworms Causing Human Disease: Filarial Worms - Elephantiasis

47. Ascaris lumbricoides is a serious parasite of humans and other vertebrate animals Causes malnutrition to more than 1 billion people worldwide including many people living in the southeastern United States Cause: by eating vegetables and other foods that are not washed properly Roundworms Causing Human Disease: Ascarid Worms

48. Roundworms Causing Human Disease: Ascarid Worms

49. Roundworms Causing Human Disease: Ascarid Worms This is why we have to have puppies “wormed” Ascarids affect many other animals Video: Worms in a dog’s heart

50. Roundworms Causing Human Disease: Hookworms • As many as one quarter of the people in the world are infected with hookworms • They suck the hosts blood causing weakness and poor growth • See chart for life cycle!