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Kingdom Animalia
Clade Ecdysozoa
Phylum Nematoda (Roundworms)
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Clade EcdysozoaAlthough the clade Ecdysozoa is defined
primarily by molecular evidence, it includesanimals that shed a tough external coat(cuticle) as they grow.
The group derives its name from ecdysis,ormolting.
The ecdysozoan clade consists of eightanimal phyla and contains more known
species than all other protist, fungus, plant,and animal groups combined.
The two largest ecdysozoan phyla,
Nematoda and Arthropoda, are among themost successful and abundant of all animal
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Phylum Nematoda Nematodes, or roundworms, are found in most
aquatic habitats, wet soil, moist tissues of plants,and the body fluids and tissues of animals.
Nematodes range in length from less than 1 mm to
more than a meter.
The cylindrical bodies of roundworms are covered
with a tough exoskeleton, the cuticle.
As the worm grows, it periodically sheds its old
cuticle and secretes a new, larger one. Nematodes have an alimentary tract and use the
fluid in their pseudocoelom to transport nutrients,
since they lack a circulatory system.
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Phylum Nematoda
Nematodes usually reproduce sexually.
The sexes are separate in most species, and
fertilization is internal.
Females may lay 100,000 or more fertilized eggs
per day.The zygotes of most nematodes are resistant
cells that can survive harsh conditions.
Free-living nematodes play a major role in
decomposition and nutrient recycling, but little is
known about most species.
Other species of nematodes parasitize animals,
including some species that benefit humans by
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Nematoda: Parasitic
Filarial WormGuinea Worm
Hook Worm
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Trichinella spiralis
Trichinella spiralis causes trichinosis when the
nematode worms encyst in a variety of humanorgans, including skeletal muscle. Humans acquire this nematode by eating
undercooked meat that has juvenile wormsencysted in the muscle tissue.
Parasitic nematodes hijack cellular functions oftheir hosts to evade their immune systems.
Some species inject molecules that induce thedevelopment of root cells that provide nutrients
to the parasites. Trichenella in human muscle cells controls the
expression of muscle cell genes that code forproteins that make the cell elastic enough to
house the nematode.
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Pork Round Worm
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Trichinella Spiralis Whole Mount
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Loa Loa
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Loa Loa
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Dirofilaria
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Adult worms1 live in the lumen of the small intestine. A female may produce up to 240,000 eggsper day, which are passed with the feces 2. Fertile eggs embryonate and become infective after18 days to several weeks 3, depending on the environmental conditions (optimum: moist, warm,shaded soil). After infective eggs are swallowed 4, the larvae hatch 5, invade the intestinalmucosa, and are carried via the portal, then systemic circulation to the lungs 6 . The larvaemature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree
to the throat, and are swallowed 7. Upon reaching the small intestine, they develop into adultworms 1. Between 2 and 3 months are required from ingestion of the infective eggs to ovipositionby the adult female. Adult worms can live 1 to 2 years.
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than females and possess a hooked
tail.
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Ascaris
http://www.curezone.com/image_gallery/parasites/ascaris/default.asp?i=11&n=247/30/2019 Lab 12 Nematoda
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Ascaris Infection
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Ascaris Male
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Ascaris Female
Ovary Oviduct Females have a pair of ovariesattached to an oviduct
Each oviduct becomes a tubularuterus, forming a vagina that opens
externally through a genital pore
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Lab Instructions: View all organisms listed in the chart
above in the microscope, stereoscope, preserved or on the
observation tray. Draw each organism in your lab notebook
and note the distinguishable characteristics of each. Review
internal anatomy of each organism.
Organism (Scienctific
Name)
Common
Name
Vertebrate
Habitat
Ascaris lumbricoides (Sl)
& (Sp)
Pork Round
Worm
Intestines
Dirofilaria (Sl) Dog Round
Worm
Lymph Vessels
Loa Loa(Sl) N/A Eye
Trichinella spiralis (Sl) Pork Round
Worm
Muscles