ABSTRACT
Nematodes have been described as being the most numerous and most widely distributed group of multicellular organisms in the world (Bogoyavienskii et al., 1974). They are parasites of animals and plants, as well as free-living bacterial feeders, which thrive in marine, freshwater, and terrestrial habitats. Although only some 15,000 species of nematodes have been described, it has been estimated that there are at least 500,000 species (Poinar, 1983). The soil is one of the most important habitats of nematodes. They constitute by far the major component of the fauna in various soils, of which they make up > 90% in numbers and ~ 10% of the total biomass (Kevan, 1965). Soil nematodes can be classified as primary consumers of plant tissues or as decomposers: bacterivorous, fungivorous, predaceous, or omnivorous (Freckman, 1982). The relationship in numbers between species of plant-feeding nematodes and decomposers obviously depends to a large extent on the nature of the vegetation and its condition. For example, a 21% plantparasitic makeup of the nematode population has been recorded in an undisturbed ecosystem, whereas in a disturbed environment, it rose to 35% (Ferris, 1982).
