The Energetics of Plant Parasitic Nematodes-a Review

Abstract

The mean size of tylenchid species that lack saccate females is significantly less than that of the bacterial-feeding Rhabditida. This suggests that the body size of these plant parasites is limited by a factor other than that imposed on all nematodes by the soil environment. The trophic mode of feeding with a stomatostylet may limit the food intake of some species because a limited maximum number of cells can be attacked each day and each possesses a relatively small volume of extractable contents. The major adaptation overcoming this limitation is the ability of several genera with saccate females to modify and enlarge the plant cells on which they feed. The associated increase in female size results in enhanced fecundity rather than an increase in egg size, which seems unnecessary for either prolonged dormancy or successful invasion of plants after hatching. The modification of plant cells by saccate genera raises feeding rates to an extent that growth of large females does not overprolong the developmental period. Feeding by these saccate females at high density may have a pathogenic effect by reducing the energy available for root growth and maintenance. Further study of the energetics of tylenchids may contribute to our understanding of the pathogenicity of these important plant parasites.