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[[Image:Soybean cyst nematode EM.jpg|thumb|right|150px|Soybean Cyst Nematode and Egg, Scanning Electron Micrograph - Wikimedia Commons]]

[[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]]

[[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

== The Nematodes ==

== The Nematodes ==

=== Recognition Features ===

=== Recognition Features ===

*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).

*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.

*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.

*A muscular pharynx is needed to pump food into the intestine

*The shape of the pharynx is characteristic in some groups.

*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).

*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 sexes are separate:

**the female tail generally ends in a blunt point

**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 they differ in shape and size between species, they are very useful for identification.

**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).

*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:

*Other modifications of the cuticle on both male and female nematodes useful for identification include:

**'''alae''' (wing-like protrusions)

**'''alae''' (wing-like protrusions)

**'''vesicles''' (swellings around the whole circumference of the body).

**'''vesicles''' (swellings around the whole circumference of the body)

*The heads of some nematodes have structures such as:

*The heads of some nematodes have structures such as:

**leaf-like lips around the mouth (the '''leaf-crown''')

**leaf-like lips around the mouth (the '''leaf-crown''')

**a '''buccal cavity'''

**a '''buccal cavity'''

**'''teeth''' or '''cutting plates'''.

**'''teeth''' or '''cutting plates'''

=== Feeding Habits ===

=== Feeding Habits ===

*Many intestinal nematodes are closely applied to the mucosal surface.

*Many intestinal nematodes are closely applied to the mucosal surface

*Some swallow ingesta and/or host secretions.

*Some swallow ingesta and/or host secretions.

*Others suck a plug of mucosa into the buccal cavity (plug feeders), leaving a circular ulcer.

*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.

*Yet others bury their heads deep into the mucosa and suck blood

egg → L1 → L2 → L3 → L4 → adult

egg → L1 → L2 → L3 → L4 → adult

*With a moult in between each larval stage.

*With a moult in between each larval stage

*But there are many variations on this theme!

*But there are many variations on this theme

=== Nematode Eggs ===

=== Nematode Eggs ===

These vary greatly in appearance and are very useful for diagnosis as they can often be detected and counted in faecal samples.

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.

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

*[[Metastrongyloidae]]

*[[Metastrongyloidae]]

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"'''.

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"'''

'''NON-BURSATE'''

'''NON-BURSATE'''

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).

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)