The Structure of the Helminth Cuticle

Abstract

Publisher Summary This chapter discusses the structure of helminth cuticle. The following groups and species are considered: Turbellaria (Kronborgia amphipodicola), Monogenea (various species), Digenea (Fasciola hepatica and various other species), Cestodaria (Gyrocotyle urna), Cestoda (various species), Nematoda (various species), and Acanthocephala (Polymorphus minutus). In the Digenea, the change from miracidium to sporocyst also involves shedding of the ciliated epidermal cells and the formation of a syncytial epidermis from cells, which lie below the muscles. Cestodaria are either monogeneans or occupy a phylogenetic position between the monogeneans and the cestodes. The development of the epidermis of adult cestodes still needs much work to clarify the situation, especially from the embryological point of view. The epidermis of adult cestodes has been confirmed as an outer cytoplasmic syncytial epidermis, which is covered with microvilli bearing electron-dense spine-like tips, and in cytoplasmic continuity with nucleated cell-like bodies in the parenchyma. The cuticle of many different stages and species of nematode is examined with the electron microscope, and a certain type of cuticle structure appears to be common to most larval nematodes and also to some adults. Several examples of moulting in nematodes have been described, and it would appear that moulting differs in different types of nematode and sometimes in different stages of the life cycle. The body wall of some larval stages of two acanthocephalans has been described by means of electron microscopy and shown to be rather similar to that of the adult.