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==Overview==

==Overview==

The structure of a nematode is intimately related to its function and its life cycle. Although there are common traits throughout the phylum there is also great diversity allowing each species to occupy a niche in which it may thrive.

The structure of a nematode is intimately related to its function and its life cycle. Although there are common traits throughout the phylum there is also great diversity allowing each species to occupy a niche in which it may thrive.

Morphological differences in the cuticle are regularly used to identify different species of nematodes, though the functions of these are not all completely understood.

Morphological differences in the cuticle are regularly used to identify different species of nematodes, though the functions of these are not all completely understood.

*'''Annulations''' - Transverse lines in cuticle, possibly used as anchoring points in locomotion

*'''Annulations''' - Transverse lines in cuticle, possibly used as anchoring points in locomotion

*'''Longitudinal Ridges''' - also known as 'synlophe', seen in some [[Trichostrongylidae]] species such as ''[[Nematodirus]]''.

*'''Longitudinal Ridges''' - also known as 'synlophe', seen in some Trichostrongylidea species such as ''[[Nematodirus]]''.

*'''Alae''' or '''wings''' - Projections of the outer cuticle layer. Can appear either just at the anterior or posterior or along the entire length of the worm. In bursate males posterior alae for part of the copulatory bursa.

*'''Alae''' or '''wings''' - Projections of the outer cuticle layer. Can appear either just at the anterior or posterior or along the entire length of the worm. In [[Bursate Nematodes|bursate]] males posterior alae for part of the copulatory bursa.

*'''Spines''' - Protrusions of the cuticle on the surface of the nematode. Function unknown, could be in self defense or attachment to host.

*'''Spines''' - Protrusions of the cuticle on the surface of the nematode. Function unknown, could be in self defense or attachment to host.

*'''Inflations''' - Vesicle like swellings of the cuticle function unknown. Found in ''[[Oesophagostomum]]'' species.

*'''Inflations''' - Vesicle like swellings of the cuticle function unknown. Found in ''[[Oesophagostomum]]'' species.

Males are either monorchic (most secernentea)  or diorchic (most Adenophera), with regards to the number of testis present. The testis are tubular structures lined with epithelium and glandular tissue, sperm are produced at the end and mature as they migrate towards the shared opening of the cloaca. Many males have paired chitinous protrusion from the cloaca known as '''spicules''', these are used for attaching to a female during copulation. The spicules are easily seen under a microscope due to their chitinous structure and their position and shape may be used as an identifying feature. Sperm are ejaculated from the cloaca around the spicule, rather than through it. The sperm produced by nematodes is amoeboid and is very motile, employing the same locomotion mechanism as seen in amoeboid species.  

Males are either monorchic (most secernentea)  or diorchic (most Adenophera), with regards to the number of testis present. The testis are tubular structures lined with epithelium and glandular tissue, sperm are produced at the end and mature as they migrate towards the shared opening of the cloaca. Many males have paired chitinous protrusion from the cloaca known as '''spicules''', these are used for attaching to a female during copulation. The spicules are easily seen under a microscope due to their chitinous structure and their position and shape may be used as an identifying feature. Sperm are ejaculated from the cloaca around the spicule, rather than through it. The sperm produced by nematodes is amoeboid and is very motile, employing the same locomotion mechanism as seen in amoeboid species.  

One of the most distinctive features of some male nematodes is the presence of a copulatory bursa, seen in nematodes of the order Strongylida. Nematodes with a copulatory bursa are known as '''Bursate''', whilst those without are '''non-bursate'''. This bursa is at the posterior end of the nematode and is formed from alae with laeral rays that are used for grasping onto the body of the female during copulation.

One of the most distinctive features of some male nematodes is the presence of a copulatory bursa, seen in nematodes of the order Strongylida. Nematodes with a copulatory bursa are known as [[Bursate Nematodes|'''Bursate''']], whilst those without are [[:Category:Non-Bursate Nematodes|'''non-bursate''']]. This bursa is at the posterior end of the nematode and is formed from alae with laeral rays that are used for grasping onto the body of the female during copulation.

====Females====

====Females====

[[Image:Female nematode xsection.jpg|thumb|right|200px|Cross section of a female nematode showing the position of the uterus - I. Livingsotne - BIODIDAC]]

[[Image:Female nematode xsection.jpg|thumb|right|200px|Cross section of a female nematode showing the position of the uterus - I. Livingsotne - BIODIDAC]]

Female nematodes usually have a single genital pore through which sperm may enter the uterus and oviduct, this pore is also referred to as a vulva and may be covered by a vulval flap. The uterus may take many forms form being short and straight, long with a single bend or a coiled form. Eggs produced in the ovaries populate the oviducts and uterus and may be released as embryonated or non embroynated eggs once fertilisation has occured. A small muscular organ exists at the vulval opening of some species known as the '''ovijector''', this organ aids in the expulsion of eggs from the vulva. Unlike in male nematodes the end of the female is usually blunt ended with the anus being positioned proximally on the body wall.

Female nematodes usually have a single genital pore through which sperm may enter the uterus and oviduct, this pore is also referred to as a vulva and may be covered by a vulval flap. The uterus may take many forms form being short and straight, long with a single bend or a coiled form. Eggs produced in the ovaries populate the oviducts and uterus and may be released as embryonated or non embroynated eggs once fertilisation has occured. A small muscular organ exists at the vulval opening of some species known as the '''ovijector''', this organ aids in the expulsion of eggs from the vulva. Unlike in male nematodes the end of the female is usually blunt ended with the anus being positioned proximally on the body wall.

*http://entomology.ucdavis.edu/courses/ent156/securedocs/lectures/ENT156T3.pdf

*http://entomology.ucdavis.edu/courses/ent156/securedocs/lectures/ENT156T3.pdf

[[Category:Nematodes|A]]

[[Category:Nematodes|A]]

[[Category:To_Do_-_Parasites]]

[[Category:To_Do_-_Parasites]]

 

[[Category:Expert_Review]]

[[Category:Expert_Review]]