Difference between revisions of "Nematodes"

From WikiVet English
Jump to navigation Jump to search
m (Unprotected "Nematodes")
 
(23 intermediate revisions by 5 users not shown)
Line 1: Line 1:
{{toplink
+
#REDIRECT[[:Category:Nematodes]]
|backcolour =
 
|linkpage =Parasites
 
|linktext =PARASITES
 
|pagetype=Bugs
 
}}
 
<br>
 
 
 
== Introduction ==
 
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 pressue (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 they differ in shape and size between species, they are very useful for 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!
 
 
 
 
 
 
 
'''Superfamilies:'''
 
 
 
 
 
'''BURSATE'''
 
 
 
*[[Trichostrongyloidea]]
 
 
 
*[[Strongyloidea]]
 
 
 
*[[Ancylostomatoidea]] (Hook worms)
 
 
 
*[[Metastrongyloidae]]
 
 
 
'''NON-BURSATE'''
 
 
 
*[[Ascaridoidea]]
 
 
 
*[[Oxyuroidea]]
 
 
 
*[[Rhabditoidea]]
 
 
 
*[[Trichinelloidea]]
 
 
 
*[[Spiruroidea]]
 
 
 
*[[Filarioidea]]
 
 
 
 
 
Occlusion of pancreatic ducts sometimes happens [[Pancreas Parasitic - Pathology]]
 

Latest revision as of 21:17, 13 July 2010

Redirect to: