Phylum Nematoda - Roundworms (Ascaris)

exoskeletons that must be shed for growth
ecdysozoans secrete ____
cuticle – that sheds periodically
nematodes are covered with a proteinaceous ____
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parasite found in the intestines of animals – food contamination
ascaris is found:
1) determine sex
2) use stereoscopic microscope to look at ends of the worm
3) open animal by mid dorsal incision along the length of the body with a probe or scissors
4) pin down body wall
5) observe prepared slide of cross section body of a female
Ascaris Lab Procedure
females are larger and male’s posterior end is sharply curved
determining sex of ascaris
mouth: anterior end – 3 lips border this opening
anus: (slitlike) located ventrally near the posterior end
location of mouth and anus:
not true coelom
body cavity:
masses of coiled tubules of varying diameters fill body cavity
reproductive organs:
flattened, extending from mouth to anus – tube within a tube (outer tube is the body wall)
digestive tract:
two pale lines running laterally along the length of body in body wall
lateral lines:
consists of two longitudinal tubes lying in two lateral lines
excretory system:
requires no oxygen
so *no organs for gas exchange or circulation*
In through the mouth and absorbed by the intestinal tract
How would nourishment be taken into the body of Ascaris and circulated?
consists of a ring of nervous tissue around the anterior end of the worm, one with dorsal and one ventral nerve cord
nervous system:
Are there signs of segmentation in the body wall or in the digestive, reproductive, or excretory systems?
Mesenteries – a fold of the peritoneum (membrane) that attaches the stomach, small intestine, pancreas, spleen, and other organs to the posterior wall of the abdomen
Support system of Ascaris:
cuticle (noncellular)
epidermis (cellular)
muscular fibers
muscle from mesoderm lies at the outer boundary of the body cavity
intestine (endoderm)
body wall made up of (outside inward):
yes, a mesodermal tissue
Can you detect muscle tissue adjacent to the endodermal layer?
What is a coelom with an outer lining of mesoderm and an inner lining of endoderm?
There are two uteri that open into the female reproductive organs & sections of coiled oviducts with small lumens and some ovaries with no lumen (inside space of a cellular component or structure)
What’s inside the uteri of Ascaris when observed in cross section under the microscope?
-Long thin body that can fit through intestinal tracts
-need to host their eggs in victims to ensure their life cycle
List some features of Ascaris that are possible adaptations to parasitic life:

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