Nematodes Flashcards
(19 cards)
Where are nematodes typically found?
They are abundant in almost every habitat.
What group do Nematodes and Arthropods share, characterized by the shedding of their cuticle through ecdysis?
Ecdysozoans
What are the general characteristics of Nematodes?
Cylindrical body tapered at both ends, Eutely or cell constancy in adults, covered by non-cellular cuticle that is secreted by the syncitial hypodermis that is made up of layers of collage and sheds through ecdysis. Hormone edysone regulates molting process
What are the general characteristics of Nematodes? Part 2
locomotion through longitudinal muscles only that are arranged in 4 bands connected to nervous system via muscle arms, pseudocoelom with high hydrostatic pressure (hydrostatic skeleton), complete digestive system, free living are aerobic, parasitic are anaerobic, no specialized circulatory or excretory systems, excretion occurs through diffusion across body wall
What are the general characteristics of Nematodes? Part 3
Nervous system made up of ring shaped ganglia around pharynx and 2 nerve cords (dorsal and ventral), sensory organs include amphids near the mouth for chemo/mechanoreception, most are dioecious with males being smaller, males have copulatory spicule designed to guide/hold vulva, internal fertilization, free living typically undergo direct development while parasitic go through juvenile stages
What makes C. elegans such a useful and beneficial nematode for research and other purposes?
Well mapped genome, nervous system is fully mapped, easy genetic manipulation
What are the main 3 types of parasitic helminth nematodes transmitted through soil, that have only one host?
Ascaris, Hookworms, and pinworms
Describe the general life cycle of the soil transmitted parasites with one host.
Adults live in intestine, eggs shed with feces and infect the soil, infection occurs after ingestion of eggs (Ascaris, hookworms) or larvae (Hookworms)
Describe the general characteristics of Ascaris.
The most widespread parasitic nematode, with up to 1 billion people worldwide infected, live in small intestine, many infected individuals asymptomatic, shelled eggs can live for years in soil waiting to be ingested
Describe the life cycle of the Ascaris.
Tiny juveniles/eggs eaten, feed on intestine content, travel through blood to lymph, then the lungs, trachea, and finally the pharynx where they are swallowed and travel back to stomach and intestine to finalized development and reproduce
Describe the general characteristics of the Hookworms.
Infections were common before sewage system improved in the U.S., recent findings indicate infected current infected communities due to poor sanitation, suck blood of host intestine using plates in mouth and can cause anemia, larval worms can get through human skin or be ingested
Describe the life cycle of the Hookworm.
Eggs pass in feces, juveniles are hatched in the soil where they feed on bacteria, penetrate human skin or are ingested, migrate to lungs via circulatory system, there they travel to trachea and small intestine where adults develop and reproduce
Describe the general characteristics of the pinworm.
Most common parasitic helminth in the U.S., adults live in cecum (last part of small intestine) and large intestine, eggs develop rapidly and infective after only 6 hours, hatch in duodenum and mature in large intestine, no indirect migration
Name the three main parasitic nematodes with more than one host.
Wucheria bancrofti, Heartworms, and Guinea worms
Describe the general characteristics of Wucheria bancrofti.
Cause damage and inflammation of lymphatic system, microfillariae=young, transmitted through mosquitos
Describe the life cycle of Wucheria bancrofti.
mosquito ingests microfillariae when biting human, develop into infective juveniles, infected mosquito transmits infective juveniles through skin of human, juveniles migrate to lymph nodes, adults develop in lymphatic vessels where they reproduce microfillariae that enter bloodstream
Describe the general characteristics of heartworms.
Filiarial worm infecting heart, primary hosts are dogs and cats, intermediate hosts are mosquitoes.
Describe the life cycle of the heartworm.
(Basically same as Wucheria bancrofti without the lymph nodes)
Describe the life cycle of the Guinea worm.
Humans drink unfiltered water containing infected copepods with L3 larva, larva are released when copepods die in stomach/intestine where they mature and reproduce, fertilized female worm travels to skin surface and causes a blister to expel larvae, L1 larvae consumed by copepod where they molt twice to become L3 larvae
