Nematodes are the most numerous animals on
earth. There are nearly 20,000 described species that are Nematodas. They occur in all environments, in fresh and sea water, on land, in polar regions and deserts. They can be found in hot springs, high up mountains and in the deepest oceans regions.
In terms of the skeletal system, Nematoda are usaully called Roundworms and they get their name from their round cross section. They have long thread-like bodies and usually very small to a microscope, some parasitic members however may be a metre long. They have a simple tube-like gut with a mouth and anus. They have a perfectly cylindrical, elongated and unsegmented body structure. Most roundworms are parasitic and some of the most common species of worms in dogs and humans tend to belong to this category. Nematodes are thin, typically less than 2.5 millimetres (0.10 in) long. The smallest nematodes are microscopic, while free-living species can be as long as 5 centimetres (2.0 in). The body has ridges, rings, warts, bristles or other distinctive structures along itself.
The head of a nematode is distinct. The rest of the body is bilaterally symmetrical, the head is radially symmetrical, with sensory bristles and, solid 'head-shields' radiating outwards around the mouth. The mouth has three or six lips, which often bear a series of teeth on their inner edges. An adhesive 'caudal gland' is usually found at the tip of the tail.
Hookworms
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Caenorhabditis Elegans
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Wuchereria
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