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a)Excretory system.
-Parasitic nematodes have a more advanced excretory system.
-Aquatic species have ventral glands called renettes posterior to the pharynx that absorb waste from the pseudocoelom and empties the waste through the excretory pore.
-Their system is known as a tubular system that develops from the renette system of the
free-living worms.
-The renettes unite to form two large canals, known as the excretory canals that open to the outside by an excretory pore which is located by the head.
b)Body plan.
-Nematodes have three cell layers:
1. Ectoderm – outer tissue layer (epidermis).
2. Mesoderm – middle tissue layer (muscle).
3. Endoderm – innermost tissue layer (body cavity).
-They are known as psuedocoelomates because they have an internal cavity that is not lined with
peritoneum – therefore it is not a “true” coelom.
-They are bilaterally symmetrical.
c)Digestive system.
-One way digestive system; (food goes in one way and out another).
-The digestive tract is a linear progression, as shown below:
Mouth.
Pharynx.
Intestines.
Rectum.
Anus.
-Food is pushed through this system by hydrostatic pressure.
d)Nematodes musculature.
-The nematode body wall has only longitudinal (lengthwise) muscles.
-The muscles run from the anterior to the posterior end of the worm.
-These muscles are used for movement.
-When these muscles contract it causes the thrashing movements from head to tail.
-They lack circular muscles so they cannot crawl on dry surfaces.
jim items answered the question on February 18, 2019 at 13:31
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