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Unprotected "Nematodes"
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#REDIRECT[[:Category:Nematodes]]
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|linkpage =Parasites
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|linktext =PARASITES
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== Introduction ==
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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.
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== The Nematodes ==
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=== Recognition Features ===
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*A unique feature of the nematodes is that the fluid in the body cavity is maintained under high pressue (this is why nematodes often burst after collection).
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*They therefore have a tough elastic cuticle which often forms elaborate structures useful for identification.
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*A muscular pharynx is needed to pump food into the intestine.
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*The shape of the pharynx is characteristic in some groups.
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*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).
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*The sexes are separate:
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**the female tail generally ends in a blunt point
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**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 they differ in shape and size between species, they are very useful for identification.
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*The '''bursate nematodes''' are characterised by a large expansion of the cuticle of the male tail to form a clasping organ (the bursa).
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*Other modifications of the cuticle on both male and female nematodes useful for identification include:
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**'''alae''' (wing-like protrusions)
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**'''vesicles''' (swellings around the whole circumference of the body).
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*The heads of some nematodes have structures such as:
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**leaf-like lips around the mouth (the '''leaf-crown''')
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**a '''buccal cavity'''
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**'''teeth''' or '''cutting plates'''.
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=== Feeding Habits ===
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*Many intestinal nematodes are closely applied to the mucosal surface.
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*Some swallow ingesta and/or host secretions.
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*Others suck a plug of mucosa into the buccal cavity (plug feeders), leaving a circular ulcer.
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*Yet others bury their heads deep into the mucosa and suck blood.
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=== General Life-Cycle ===
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*The basic life-cycle is very simple:
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egg → L1 → L2 → L3 → L4 → adult
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*With a moult in between each larval stage.
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*But there are many variations on this theme!
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=== Nematode Eggs ===
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These vary greatly in appearance and are very useful for diagnosis as they can often be detected and counted in faecal samples.
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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.
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== Nematode Superfamilies ==
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'''BURSATE'''
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*[[Trichostrongyloidea]]
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*[[Strongyloidea]]
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*[[Ancylostomatoidea]] (Hook worms)
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*[[Metastrongyloidae]]
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'''NON-BURSATE'''
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*[[Ascaridoidea]]
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*[[Oxyuroidea]]
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*[[Rhabditoidea]]
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*[[Trichinelloidea]]
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*[[Spiruroidea]]
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*[[Filarioidea]]
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Occlusion of pancreatic ducts sometimes happens [[Pancreas Parasitic - Pathology]]
 

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