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General Morphology of Nematodes
> EXCRETORY
SYSTEM
EXCRETORY SYSTEM
The excretory system
presents a varied picture in the phylum as a whole. It is simplest in
the class Adenophorea where there is a single ventral excretory cell
called rennete, which opens through an excretory pore on the mid-ventral
line in the region of the oesophagus, by way of a short to long duct.
In the class Secernentea, there are two lateral excretory canals,
embedded in the lateral chords of the hypodermis. throughout most of the
body length. They are connected, anteriorly and ventrally, by a
transverse canal, forming a H or U shape. A very short duct connects the
transverse duct with the excretory pore. The terminal excretory duct is
cuticularly lined and can be observed in routine microscopic
examinations. In the Adenophorea, the terminal excretory duct is not
lined with cuticle (except in some Plectinae) thus making it difficult
to see. In a few genera, including Dorylaimus, no excretory
system has been recorded.
Considerable excretion through the digestive
tract may occur in all oematodes.
The separation of the two classes of the
Phylum into Adenophorea and Secernentea (Aphasmidia and Phasmjdia) :s
based, to some extent, on the type of the excretory system present.
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