Feeding and Digestion

Abstract

Nematodes have established themselves in nearly all possible ecological niches. Those adapted to the soil as an environment feed on many sources. Root parasitic nematodes exploit the root as their only source of nutrients and may spend their whole life cycle outside it, feeding from the surface or deeper tissues, others have evolved the capacity to invade the root and feed from cortical or stelar cells. All of them are obligate biotrophic parasites as they derive their nutrients from living cells, which they modify by pharyngeal gland secretions prior to food ingestion. In many cases food cells are transformed into highly specialised feeding structures to support nematode development and reproduction. The aim of this chapter is to summarise current knowledge of the feeding behaviour of root parasitic nematodes, first with emphasis on nematode vectors of plant viruses within the orders Triplonchida and Dorylaimida, which feed as migratory ectoparasites and second on selected examples within the Tylenchida, which have developed a highly diversified range of root parasitic strategies that culminates in sedentary endoparasitism, among which cyst and root-knot nematodes are the most economically important representatives. As cell and root tissue responses are closely related to feeding behaviour, this aspect will also be considered, however without presenting the molecular interactions in great detail. In this field of research enormous progress has been achieved in recent years and for all those interested, the book of Fenoll, Grundler and Ohl (1997) is strongly recommended. In addition, an excellent review on current approaches and progress in identifying parasitism genes in cyst and root-knot nematodes has just been published (Davis et al., 2000).