1. Phylum Nematoda Parasites and free-living
Lack cilia except in their sensory structures
Marine, freshwater, and soil habitats
Triploblastic, bilaterally symmetrical
Unsegmented vermiform (wormlike organism)

3. Phylum Nematoda External features Noncellular, collagenous cuticle
Can molt 4 times during maturation
Maintains internal hydrostatic pressure
Mechanical protection
Resists digestion by the host

5. Phylum Nematoda Longitudinal muscles are used for locomotion
Thrashing movements (can’t crawl like worms)

6. Phylum Nematoda Sensory organs
Amphids – chemoreceptors along the cuticle
Phasmids - chemoreceptors near the anus
Ocelli – eyespots found in aquatic nematodes

7. Feeding and Digestive System
Carnivores, herbivores, omnivores, saprobes(decomposers), or parasitic Complete digestive system mouth->buccal cavity->pharynx ->tubular intestine->rectum->anus Hydrostatic pressure pushes food thru

8. Other Organ Systems Glandular system Aquatic nematodes
Renettes – absorb nitrogenous waste
Tubular system
Parasitic nematodes
Renettes form a canal

9. Other Organ Systems Nervous system
Nerve ring from anterior to posterior
Also have neuroendocrine secretions involved in growth, molting, cuticle formation, and metamorphisis

10. Reproduction Sexual Dioecious-having separate sexes
Dimorphic-males are smaller than females
internal fertilization

11. Reproduction Males One testis
Bursa- used to insert their sperm into the female
males have ameboid sperm

12. Reproduction Females Pair of convoluted ovaries Oviducts become uterus
Several hundred to several hundred- thousand eggs per day
Ovovivparity – giving birth to larvae that hatched from an egg

13. Some Important Nematode Parasites of Humans
Ascaris lumbricoides
Enterobius vermicularis
Necator americanus
Trichinella spiralis
Wuchereria bancrofti

14. Ascaris lumbricoides
The Giant Intestinal Roundworm- The adult female worm can be over 30 cm long and 2-6 mm wide 800 million infected- most common parasitic worm disease in the world
the largest of the human intestinal nematodes. This is the most common parasitic worm disease in the world, very prevalent in tropical regions but rarely found also in our country. In the United States about 4 million people are infected. The adult female worm can be over 30 cm long and 2-6 mm wide. The female worm produces eggs per day.

15. Ascaris lumbricoides
Adults live in small intestines of humans Eggs exit with through feces Once the eggs are ingested, they hatch in intestine and travel to the lungs Larvae molt twice, they travel to the trachea where they are swallowed

18. Ascaris lumbricoides When Ascaris becomes a big problem. . .
Warning: those with weak stomachs need not continue viewing. Only for the HBO audiences!
When Ascaris becomes a big problem. . .

19. Enterobius vermicularis
Pinworm
Most common parasite in US
Adults live in large intestine
At night females migrate out of the anus and lay eggs on skin

20. Enterobius vermicularis
Human ingest eggs, hatch and molt 4 times in small intestine & migrate to large

22. Necator americanus Found in Southern US
Adults live in small intestine with teeth and feed on blood & tissue fluid
Females 10,000 eggs daily & pass out of body in feces
Hookworm

23. Necator americanus
Eggs hatch in warm moist soil and releases a small larva, the larva molts and becomes the infective filariform larva.
hookworms living in soil

24. Necator americanus
Humans become infected when filariform penetrates the skin (usually b/w toes) to reach our circulatory system
Outside defecation and walking barefoot maintains life cycle

26. Trichinella spiralis
The Porkworm Adults live in mucus of small intestine of humans and other mammals
Adult female
Adult male

27. Trichinella spiralis
Females birth young, larvae enter circulatory system and are carried to Skeletal (striated) Muscles
Larvae entering into Skeletal Muscle cells

28. Trichinella spiralis
Larvae encyst in muscles & remains infective for many years

29. Another host must ingest infective meat to continue the life cycle

31. Trichinella spiralis
Humans become infected by eating improperly cooked pork products Larvae encyst in stomach move to small intestine molt 4 times, turn into Adults

32. Wuchereria bancrofti
The Filarial worms In tropical countries over 250 million human infected
Lymphatic vessels return tissue fluids to circulatory system

33. Wuchereria bancrofti
Thread-like worms that live in the Lymphatic System, block the vessels This causes enlargement of various appendages: Elephantiasis
An Adult female Wuchereria bancrofti is about mm long and mm in diameter, whereas a male is about 40 mm long and 0.1 mm in diameter.

34. Elephantiasis
Warning: Pictures not for everyone!

35. Wuchereria bancrofti
Adults copulate produce microfilariae. The microfilariae released into the blood stream
A microfilaria is about µm (micrometers) long and µm thick

36. Wuchereria bancrofti
Mosquito (intermediate host) feeds on human (definitive host) ingest microfilariae and larvae molts 2 times Mosquito bites another human it injects 3rd stage larvae into human blood, molts, enters lymphatic system

38. Other Filarial Worms
Dirofilaria immitis in US parasite of dogs Adult worms live in heart, large arteries, and lungs Heartworm disease- fatal to dogs, unless give preventative medicine