The relative roles of the intestines and external surfaces in the nutrition of monogeneans, digeneans and nematodes.

Abstract

Several major groups of parasitic helminths (Monogenea, Digenea and Nematoda) possess two surfaces that are potentially absorptive in nature. These are an external surface, a tegument in the platyhelminths and cuticle in the nematodes, and the intestine. This paper discusses the relative contributions of these absorptive surfaces in the nutrition of these parasitic helminths. There are many factors that determine the availability of, and a parasite's ability to absorb nutrients via either of these surfaces, and this review discusses individually some of the more important morphological, physiological and environmental factors affecting the potential nutritional roles of these surfaces. It is clear from such a summary of previous studies that the intestines and teguments (cuticles) of helminth parasites can each serve an important nutritional role. However, insufficient data make it impossible at this time to determine the relative nutritional roles of these surfaces in any single parasitic helminth.