Phylum:
Nemathelminthes
Nematoda
Ascaris
By
Assist. lecturer Maytham A. Alwan
Nematoda :introduction
Nematodes
Appearance and Morphology
1. Variable length, 1 mm to several meters.
2. Most nematodes have a cylindrical form, tapering at either end, and
the body is covered by a colourless, somewhat translucent(the cuticle
which may form specialized structures (e.g., alae).
• The cuticle is secreted by the underlying hypodermis, which projects
into the body cavity forming two lateral cords, which carry the
excretory canals, and a dorsal and ventral cord carrying the nerves
.The muscle cells, arranged longitudinally, lie between the hypodermis
and the body cavity.
Characteristics of the Nematoda
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Nematoda:Structure and function
3. Usually sexually dimorphic (separated sex) with males smaller than
females.
4. The body is bilateral symmetry.
5. Most of the internal organs are filamentous and suspended in the fluidfilled body cavity.
A. The digestive system is tubular. The mouth of many nematodes is
a simple opening which may be Surrounded by two or three lips, and
leads directly into the oesophagus. In others, such as the strongyloids,
it is large, and opens into a buccal capsule, which may contain teeth.
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Morphology
B. The reproductive systems consist of filamentous tubes.
The female organs comprise ovary, oviduct and Spicules uterus,
which may be paired, ending in a common short vagina which opens
at the vulva.
• The male organs consist of a single continuous testis
and a vas deferens terminating in an ejaculatory duct into the cloaca.
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Characteristics of the Nematoda
Digestive system
Assist lec. Maytham Al-Shabbani
Nervous system
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Excretory system
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Characteristics of the Phylum Nematoda
Reproductive system consists of
tubular organs lying in the
pseudocoelom.
MALE nematodes are generally
smaller in size.
Assist lec. Maytham Al-Shabbani
Characteristics of the Phylum Nematoda
FEMALE nematodes are larger
in size. The female
reproductive organs are
doubled.
Assist lec. Maytham Al-Shabbani
Ascaris
Kingdom: Animalia
Phylum: Nemathelminthes
Class: Nematoda
Order: Ascaroidea
Family: Ascarididae
Genus: Ascaris
Species: A. lumbricoides (human), A. suum (pigs)
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Morphology
•
Adult: The adults are cylindrical in shape, creamywhite or pinkish in color. The female averages 20-35cm
in length, the largest 49cm. The male is smaller,
averaging 15-31cm in length and distinctly more slender
than the female. The typical curled tail with a pair sickle
like copulatory spines. On the tip of the head there are
three lips, arranged as a Chinese word “ 品 ”. They
have a complete digestive tract. Reproductive organs are
tubular. male has a single reproductive tubule. The
female has two reproductive tubules and the vulva is
ventrally located at the posterior part of the anterior 1/3
of the body.
Assist lec. Maytham Al-Shabbani
Adult worm of A. lumbricoides
Assist lec. Maytham Al-Shabbani
The lips of Ascaris lumbricoides
The three lips are seen
at the anterior end. The
margin of each lip is lined
with minute teeth which
are not visible at this
magnification.
Assist lec. Maytham Al-Shabbani
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Assist lec. Maytham Al-Shabbani
15
•
Egg: There are three kinds of the eggs. They are fertilized
eggs, unfertilized eggs and decorticated eggs. We usually
describe an egg in 5 aspects: size, color, shape, shell and content.
Assist lec. Maytham Al-Shabbani
• Egg: There are three kinds of the eggs. They are fertilized
eggs, unfertilized eggs and decorticated eggs. We usually
describe an egg in 5 aspects: size, color, shape, shell and
content.
Semilunar space
Vitelline layer (1st)
One cell stage
2nd layer (thick)
3rd layer outer coarse
albuminous layer (regular)
Fig . : Ascaris lumbricoides- Egg
Fig . : life cycle of Ascaris lumbricoides
Assist lec. Maytham Al-Shabbani