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Phylum Nematoda (roundworms). 12,000 spp. free-living & parasitic ubiquitous important in medicine and horticulture. Morphology. slender, elongate, & most
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Phylum Nematoda (roundworms)
• 12,000 spp.• free-living & parasitic• ubiquitous• important in medicine and horticulture
Morphology• slender, elongate, & most <2.5mm• cuticle containing collagen• longitudinal muscles only - producing
eel-like undulations• circumpharyngeal nerve ring and
longitudinal nerve cords
Reproduction & Development
• dioecious• hermaphrodites• egg storage in the uterus• may produce 200,000 eggs/day• protostomes
Ascaris (egg and juvenile)
Ascaris (female dissection)
Enterobius - “pinworm”• 16% adults & 30 %
children in US are infected
• female deposits eggs at night in the perianal region
• complex life cycle
Enterobius- male & female
Enterobius (female)
Necator – “hook worm”• mouth parts are designed
to bite onto the lining of the intestine, abrade the surface and suck the patients blood.
• many people show no outward symptoms of disease.
• the severity of the disease depends on the number of worms per individual, the nutritional state of the patient and the species of hookworm
Necator
Trichinella• causes trichinosis
• acquired by eating undercooked pork
• larvae encyst in host muscle tissue
Dirofilaria – dog heart worm
Wuchereria – causes elephantiasis
• afflicts ~ 100 million and is said to be one of the world’s fastest spreading diseases
• the parasite clogs the lymph vessels of the host.
Dracunculus