Nematode Structure and Function

A unique feature of the nematodes is that the fluid in the body cavity is maintained under high pressure (this is why nematodes often burst after collection)
They therefore have a tough elastic cuticle which often forms elaborate structures useful for identification
A muscular pharynx is needed to pump food into the intestine
The shape of the pharynx is characteristic in some groups
There is a nerve ring around the pharynx and four longitudinal nerves with ganglia that co-ordinate movement (many anthelmintics act by disrupting neuromuscular co-ordination)
The sexes are separate:
- the female tail generally ends in a blunt point
- males usually have two chitinous rods that can be protruded through the cloaca to hold the female - these are called spicules and, being chitinous, are easily seen under the microscope. As these differ in shape and size between species, they are very useful in identification
The bursate nematodes are characterised by a large expansion of the cuticle of the male tail to form a clasping organ (the bursa)
Other modifications of the cuticle on both male and female nematodes useful for identification include:
- alae (wing-like protrusions)
- vesicles (swellings around the whole circumference of the body)
The heads of some nematodes have structures such as:
- leaf-like lips around the mouth (the leaf-crown)
- a buccal cavity
- teeth or cutting plates

Many intestinal nematodes are closely applied to the mucosal surface
Some swallow ingesta and/or host secretions.
Others suck a plug of mucosa into the buccal cavity (plug feeders), leaving a circular ulcer
Yet others bury their heads deep into the mucosa and suck blood