Transcript Phylum Nematoda Chapter

The Ecdysozoa
• The Ecdysozoa include the following phyla:
Arthropoda, Onychophora, Tardigrada, Kinorhyncha,
Priapulida, Loricifera, Nematoda and Nematomorpha.
The Ecdysozoa
• Characteristic shared by ecdysozoans
– Three-layered cuticle composed of organic
material, which is periodically molted as the
animal grows.
– The process of molting is called ecdysis and
gives the group its name.
– The Ecdysozoans lack locomotory cilia,
produce mostly amoeboid sperm.
– Their embryos do not undergo spiral
cleavage as in most other protostomes.
Phylum Nematoda
the roundworms
Phylum Nematoda
Nematodes are among the most abundant animals on earth
- over 25,000 species have been described.
Majority of nematodes are free-living in every conceivable
habitat.
• free-living species are commonly microscopic in size.
• A few species cause disease of great importance to
humans and domestic and wild plants and animals.
Phylum Nematoda
• If all the matter in the universe except the
nematodes were swept away,…we should
find our world’s mountains, hills, vales,
rivers, lakes and oceans represented by a
thin film of nematodes.
– N.A. Cobb (1914, Yearbook of the United States
Department of Agriculture)
Phylum Nematoda
• Parasitic and free-living
• Numerous and diverse
– 6.7 ml of coastal mud
• 1,074 individuals
• 236 species
– Rotting apple:
• 90 thousand individuals
– Farmland:
• 9 billion per acre
Phylum Nematoda
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Roundworms
Dioecious (mostly)
Tapered at both ends
Pseudocoelomate
– Pseudocoel
• Complete digestive system
– Mouth and anus
Pseudocoelomate Characteristics
“false” body cavity
ectoderm
pseudocoelom
mesoderm
Gut
endoderm
the pseudocoelom is lined by mesoderm
on ONE side only
Characteristics of the Phylum Nematoda
Phylum Nematoda
• Triradiate
pharynx
– Pharynx between
mouth and
esophagus
Photo by Agustín Jimenez
Phylum Nematoda
• Body covered by:
• Cuticle
– Noncellular
– Molts
• 4 times during development
Elaboration of Cuticle
• Aspidodera
Phylum Nematoda
• Movement
– Longitudinal muscles
– Hydrostatic skeleton
• Fluid filled pseudocoel
– Cuticle
• Contraction of muscles
• Antagonized by pressure of pseudocoel
and hydrostatic skeleton
Tube within a tube
Female
Esophagus
Uterus
Vulva
Tube within a tube
• Male
Cloaca = common
area for openings of
genital pore and anus
Copulatory Spicules
Hold vulva open during copulation
Reproduction
• Dioecious
• Some Monoecious (rare)
• Parthenogenesis
– Females reproduce without males
– Unfertilized eggs develop into new individuals
– Sometimes systems are mixed (heterogamy)
• Mate Finding
– Pheromones
– Thigmotaxis (papillae near reproductive structures)
Mating Behavior
• Male coils tail
around female and
searches for vulva.
Papillae
• Sensory structures
Characteristics of the Phylum Nematoda
Nematode development is similar in all nematodes.
Consists of 4 juvenile stages between the egg and adult. Each
stage is separated by a molt of the cuticle.
Hatch
Egg
M1
J1
M2
J2
M3
J3
M4
J4
Adult
Juvenile stages may be passed within the egg, free-living in soil,
parasitic in an intermediate host, or parasitic in definitive host.
Ecology
• Many nematodes are important parasites of both
plants and animals.
parasite of soybean
plants
parasite of tomato
plants
Parasitic Nematodes
Order Oxyurida
Rhoden and Bolek (2011)
Order Oxyurida
Rhoden and Bolek (2011)
Order Oxyurida
• Enterobius vermicularis
– Pinworms
– Enterobiasis
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Large esophageal bulb
Sharp, pointed tail
Alae at anterior end
Cosmopolitan
Common in people
Relatively unpathological
• Direct life cycle
• Adults live in ileocecal
region of intestine
(wander throughout gut)
• Feed on bacteria and
organic material from
cells
• At night, females
migrate to anus and lay
eggs (up to 16,000 each)
• Embryonates within 6
hours
• Infection via ingestion of
embryonated eggs
• Or may hatch on
perianal folds and
wander up intestine
Symptoms and Pathology
• 1/3 asymptomatic
• Pruritus
• Lesions from feeding not significant
– Secondary infections can occur
• Itching can lead to secondary infections
Pinworm Neurosis
• Nervousness
– Fidgeting, restlessness, irritable, nail biting,
nose picking
– Due to toxemia and damage of epithelium
• Children
• Parents
– Obsessive cleaning
Diagnosis
• Scotch tape test
• Flashlight test
• Mebendazole
• Treat entire family
Diagnosis of Enterobius vermicularis
DIAGNOSIS -
Use of double-stick tape
on a tongue depresser.
This is pressed against
the perianal folds where
eggs will stick to the tape.
Tape is then stuck onto a
microscope slide and
examined for eggs.
Enterobius vermicularis
Almost anybody can become
infected with this parasite. No
social class is exempt. These
parasites soon become "family
affairs".
Once one person, usually a child
becomes infected, other family
members will undoubtedly also
become infected.
Epidemiology
• Very Prolific
• Eggs build up fast
– Clothing and bedding
– Eggs very light and float
– Easily distributed
• Eggs viable for up to a
week
Prevention and Control
• Not very serious
• Good hygiene
Horse Pinworms, Oxyuris equi
Horse Pinworms, Oxyuris equi
Horse Pinworms, Oxyuris equi
Guinea worm (Dracunculus medinensis):
Guinea worm (Dracunculus medinensis):
Guinea worm (Dracunculus medinensis):
• Transmitted by infected copepods in drinking water
• Juveniles move into the body cavity
• Female adult migrates to the subcutaneous tissue, causes an ulcer/blister,
and releases juveniles through hole when host comes in contact with water
Guinea worm (Dracunculus medinensis):
Traditionally removed by winding the worm around a
stick over the course of several days
• This may be the basis for the Caduceus symbol used in
the medical field
Juvenile Dracunculus medinensis and
Copepod Intermediate host
Life Cycle
Drinking Water
Guinea worm sufferers often try to ease the
burning pain caused by the blister by stepping
into water—the very same source of drinking
water for their community.
Guinea worm (Dracunculus medinensis):
• Female worms cause allergic reactions during blister
formation, causing an intense burning pain producing
allergic reactions (rashes, nausea, diarrhea, dizziness,
and localized edema).
• When the blister bursts, allergic reactions subside, but
skin ulcers form, through which the worm can
protrude.
• Only when the worm is removed is healing complete.
Death of adult worms in joints can lead to arthritis and
paralysis in the spinal cord.
Carter Center: Guinea Worm
Eradication
Jimmy Carter
39th President of the United States
Distribution
Controlled Immersion
Current Distribution