Portal de Periódicos da CAPES

The Structure and Composition of the Helminth Cuticle

1967; Elsevier BV; Linguagem: Inglês

10.1016/s0065-308x(08)60450-9

2163-6079

D.L. Lee,

Helminth infection and control

This chapter focuses on the structure and composition of the helminth cuticle. Various modern techniques have been applied to the study of the cuticle and have improved the knowledge of the structure and function of the outer covering of the parasitic Platyhelminthes and Acanthocephala. There are three major groups of helminthes: the parasitic Platyhelminthes, the Nematoda, and the Acanthocephala. The "cuticle" of the digenetic trematodes and the cestodes is a syncytial cytoplasmic covering continuous with nucleated portions of the cytoplasm situated in the parenchyma beneath the muscle layers and is to be regarded as an epidermis. The epidermis of cestodes is covered with numerous microvilli, which greatly increase the absorptive surface of the worm. The epidermis of the digenetic trematodes is devoid of microvilli, but contains mitochondria and enzymes and numerous vacuoles and vesicles that appear to be associated with the uptake, excretion, or secretion of materials across the epidermis. The Acanthocephala are closely related to the cestodes because of the lack of a gut and because they possess a proboscis. The presence of pores and canals in the cuticle and striped layer of the body wall of the Acanthocephala indicates that nutrients are absorbed through these openings in the body wall, rather than through the general body surface. The nematode cuticle has a complex and varied structure with three main layers which are usually subdivided into further layers. The cuticle of nematodes seems to be composed of collagen plus small amounts of carbohydrate and lipid, and the outer layer is usually toughened or strengthened in some way. The presence of enzymes and RNA in the cuticle of nematodes shows that it is not an inert secretion but is a metabolically active structure.