Nematodes are microscopic worms that live in the soil. Many nematodes are harmless to plants, but there are many others that are pathogenic. Nematodes are characterized by a smooth narrow cylindrical unsegmented body tapered at both ends. The microscopic free-living forms are found in all parts of the world, where they play an important role in the destruction and recycling of organic matter.  
The word Nematoda comes from the Greek words nematos, meaning thread, and eidos, meaning form. Nematodes are the most numerous multicellular animals on earth. There are nearly 20,000 described species classified in the phylum Nemata. They are so abundant, that 8 out of 10 animals are nematodes.
Parasitic Nematodes Home Page - UNL
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