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Phylum Nematoda Parasites and free-living

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Presentation on theme: "Phylum Nematoda Parasites and free-living"— Presentation transcript:

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


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