DIVERSITY:

If all the matter in the universe except nematodes were swept away, our world would still be recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites. (N. A. COBB)

Nematodes are one of the most abundant of all animal (metazoan) groups. There are about 30,000 described species. Approximately 50% are marine and are very abundant in all oceans from intertidal zones to several hundred meters depth. Some have been recovered from samples taken at 30,000 feet. Marine forms are also abundant in Arctic and Antarctic oceans at depths of 500 or more meters. Approximately 15% are parasites of animals, both invertebrate and vertebrate, and include man and domesticated animals. Parasites of plants and free-living nematodes account for 10% and 25% of nematodes, respectively. Nematodes occur in practically all soils and are common in high mountain soils 14,000 feet or more. In some agricultural soils plant-parasitic species are known to occur to depths of at least 17 feet. Some nematodes are found worldwide (also termed cosmopolitan) while the distribution of others is restricted by geographical or environmental conditions. The distribution of many species has been influenced by human activities. Some parasites have very broad host ranges while others have very narrow ones. All nematodes live in an "aquatic" (wet or liquid) environment and are only active when in moist habitats. Even soil dwelling forms are living in the film of moisture that lines soil pores. It is not uncommon for several species of nematodes to be found in the same host or habitat.

References:

  1. Maggenti, A.R. 1981. General Nematology. Springer-Verlag, New York. 372 pages.
  2. Ayoub, S.M. 1980. Plant Nematology An Agricultural Training Aid. NemaAid Publication, Sacramento, CA. 195 pages.

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