Four of every five multicellular animals on theplanet are nematodes. They occupy any niche that provides an available sourceof organic carbon in marine, freshwater and terrestrial environments; they arethe planet’s most abundant metazoa. Nematodes are an evolutionarily successfulgroup of organisms.
In soil, some nematodes feed on higher plants, some onfungi or bacteria; others are carnivores or omnivores. They range inreproductive potential from explosive opportunists to conservative survivalists.The phylum Nematoda comprises the classes Secernentea and Adenophorea. TheSecernentea are almost exclusively terrestrial, only rarely being freshwater ormarine, whereas the Adenophorea occupy niches in all three habitats. Almost 20,000nematode species have been described and millions of nematodes can occupy 1 m2of soil.
There can be 50 different species in a handful of soil and a 100-mlcore of soil yields sufficient individuals for reliable analysis. Routine analysesof nematode fauna provide a basis for environmental management, remediation andconservation decisions. Mostimportantly, nematodes have variable responses to stress factors; some speciesare extremely sensitive to pollutants and others extremely tolerant. It is difficult, and perhaps unimportant, tocalculate how many species are present when determining the biodiversity of anarea. Recent research indicates that simple analyses of in situ nematodefaunae at family level provide a wealth of information on the nature ofdecomposition pathways and soil nutrient status. The analyses also indicateeffects of agricultural practices and contaminants on the functioning of thesoil food web.
As a useful index ofbioindicators in ecotoxicological diagnosis, the prospect of soil nematodeapplication was of potential. Evidencecontinues to grow to show that their community structures can help to track globalwarming and, from a retrospective point of view, their global distributions mayeven reflect the processes of continental drift and their biochemistry, thehistory of the Earth’s chemosphere.