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| | [[Image:Mononchidae eating a Mononchidae.jpg|thumb|right|150px|Mononchidae eating a Mononchidae - 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. | | 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. |
| − | Occlusion of pancreatic ducts sometimes happens [[Pancreas Parasitic - Pathology]] | + | Occlusion of [[Pancreas Parasitic - Pathology|pancreatic ducts]] sometimes happens. |
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| − | === Recognition Features ===
| + | [[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)
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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 these differ in shape and size between species, they are very useful in 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 === | | === General Life-Cycle === |