30 Parasitic Nematodes

Abstract

I. THE NEMATODE WORLD
Of every five animals on the planet, four are nematodes (Platt 1994). The vast majority are free-living microbivores, but many species have adopted a parasitic lifestyle. Most plants and animals have at least one parasitic nematode species uniquely adapted to exploit the concentration of food and resources that the host species represents. The reasons for the success of the Nematoda as parasites probably include the presence of an environmentally protective cuticle, facultative diapause (like the dauer stage of Caenorhabditis elegans), biochemical adaptations to existence in extreme conditions, and the use of a variety of reproductive strategies. Some parasitic nematodes are the subject of extensive research efforts, often aimed at understanding their lifestyle and ecology so as to control or manage them better.

The choice of the free-living rhabditid C. elegans as a model for metazoan development has been fortunate for the study of other nematodes, particularly parasites. Although only distantly related to most parasitic species, C. elegans displays the morphological conservatism of the phylum and shares structures found to be important to parasitic species. It also has a characteristic nematode biochemistry and has proved to be sensitive to all the major nematicidal drugs. In this chapter, we first provide an overview of the diversity and importance of parasitic nematodes and subsequently describe three systems where research on C. elegans is having a significant impact on parasitology.

Historically, the study of nematodes has fragmented into three major branches (plant nematology, animal parasitology, and free-living nematology) that have...