phylum nematoda parasites and free-living lack cilia except in their sensory structures marine,...
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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)
Phylum NematodaExternal features
•Noncellular, collagenous cuticle
• Can molt 4 times during maturation
• Maintains internal hydrostatic pressure
• Mechanical protection• Resists digestion by the host
Phylum Nematoda• Longitudinal muscles are used for
locomotion• Thrashing movements (can’t crawl like
worms)
Phylum Nematoda•Sensory organs
•Amphids – chemoreceptors along the cuticle
•Phasmids - chemoreceptors near the anus
•Ocelli – eyespots found in aquatic nematodes
Feeding and Digestive SystemCarnivores, herbivores, omnivores, saprobes(decomposers), or parasitic
Complete digestive systemmouth->buccal cavity->pharynx ->tubular intestine->rectum->anus
Hydrostatic pressure pushes food thru
Other Organ SystemsGlandular system
•Aquatic nematodes•Renettes – absorb nitrogenous waste
Tubular system•Parasitic nematodes•Renettes form a canal
Other Organ Systems
•Nervous system•Nerve ring from anterior to posterior
•Also have neuroendocrine secretions involved in growth, molting, cuticle formation, and metamorphisis
ReproductionSexual•Dioecious-having separate sexes
•Dimorphic-males are smaller than females
•internal fertilization
Reproduction•Males
•One testis•Bursa- used to insert their sperm into the female
•males have ameboid sperm
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
Some Important Nematode Parasites of Humans
•Ascaris lumbricoides•Enterobius vermicularis•Necator americanus•Trichinella spiralis•Wuchereria bancrofti
Ascaris lumbricoidesThe 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
Ascaris lumbricoidesAdults live in small intestines of
humansEggs 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
Ascaris lumbricoidesWarning: those with weak stomachs need not
continue viewing. Only for the HBO audiences!
When Ascaris becomes a big problem. . .
Enterobius vermicularisPinwormMost common parasite in US
Adults live in large intestine
At night females migrate out of the anus and lay eggs on skin
Enterobius vermicularisHuman ingest eggs, hatch and molt 4 times in small intestine & migrate to large
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
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
Necator americanusHumans become infected when filariform penetrates the skin (usually b/w toes) to reach our circulatory system
Trichinella spiralisThe PorkwormAdults live in mucus of small intestine of humans and other mammals
Adult female Adult male
Trichinella spiralisFemales birth young, larvae enter circulatory system and are carried to Skeletal (striated) Muscles
Larvae entering into Skeletal Muscle cells
Trichinella spiralisLarvae encyst in muscles & remains infective for many years
Another host must ingest infective meat to continue the life cycle
Trichinella spiralisHumans become infected by eating improperly cooked pork products
Larvae encyst in stomach move to small intestine molt 4 times, turn into Adults
Wuchereria bancroftiThe Filarial wormsIn tropical countries over 250 million human infected
Wuchereria bancroftiThread-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 80-100 mm long and 0.24-0.30 mm in diameter, whereas a male is about 40 mm long and 0.1 mm in diameter.
ElephantiasisWarning: Pictures not for everyone!
Wuchereria bancroftiAdults copulate produce microfilariae.
The microfilariae released into the blood stream
A microfilaria is about 240-300 µm (micrometers) long and 7.5-10 µm thick
Wuchereria bancroftiMosquito (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
Other Filarial WormsDirofilaria immitis in US parasite of dogs
Adult worms live in heart, large arteries, and lungs
Heartworm disease- fatal to dogs, unless give preventative medicine