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== Introduction ==
[[Image:Soybean cyst nematode EM.jpg|thumb|right|150px|Soybean Cyst Nematode and Egg, Scanning Electron Micrograph - Wikimedia Commons]]
[[Image:Mononchidae eating a Mononchidae.jpg|thumb|right|150px|Mononchidae eating a Mononchidae - Wikimedia Commons]]
Nematodes are one of the most prolific life-forms on this planet. Most are free-living, with species adapted to every imaginable habitat. Some are parasitic on plants, and others on animals. The animal parasitic nematodes form a large and diverse array of organisms.
== The Nematodes ==
=== Recognition Features ===
*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'''
=== Feeding Habits ===
*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
=== General Life-Cycle ===
*The basic life-cycle is very simple:
**egg → L1 → L2 → L3 → L4 → adult
*With a moult in between each larval stage
*But there are many variations on this theme
=== Nematode Eggs ===
*These vary greatly in appearance and are very useful for diagnosis as they can often be detected and counted in faecal samples
*NOTE: we use the typical '''strongyle''' egg to provide us with a yard-stick for comparing sizes. A "large egg", for example, means larger than a strongyle egg. A typical strongyle egg is approximately '''80µm''' long
== Nematode Superfamilies ==
<big>
[[:Category:Bursate Nematodes|'''BURSATE''']]
*[[Trichostrongyloidea]]
*[[Strongyloidea]]
*[[Ancylostomatoidea]] (Hook worms)
*[[Metastrongyloidae]]</big>
NOTE: the Trichostrongyloidea, Strongyloidea and hookworms are very closely related, and are often collectively known as '''"the strongyles"'''. Typically, they produce almost identical eggs, called '''"typical strongyle eggs"'''.
<big>[[:Category:Non-Bursate Nematodes|'''NON-BURSATE''']]
*[[Ascaridoidea]]
*[[Oxyuroidea]]
*[[Rhabditoidea]]
*[[Trichinelloidea]]
*[[Spiruroidea]]
*[[Filarioidea]]</big>
From the veterinary view-point, the nematodes are most conveniently grouped into '''superfamilies''' because their members often have similar life-cycles and epidemiological features. Superfamily names end in -oidea (the anglicised form is -oid, as in trichostrongyloid).
== Nematodes of Different Species ==
[[:Category:Cattle Nematodes|Cattle Nematodes]]
[[:Category:Sheep Nematodes|Sheep Nematodes]]
[[:Category:Goat Nematodes|Goat Nematodes]]
[[Horses]]
[[Pigs]]
[[Poultry]]
[[Small Animals]]
[[Endoparasites - Donkey|Donkey]]
Occlusion of pancreatic ducts sometimes happens [[Pancreas Parasitic - Pathology]]
[[Category:Helminths]]
[[Category:Helminths]]