Trichinella spiralis: Fine structure of body wall with special reference to formation and moulting of cuticle

Abstract

The body wall of the immediate postembryonic juvenile, the preinfective juvenile, the infective juvenile, the moulting juvenile in the host's intestine and the adult of Trichinella spiralis was examined with the electron microscope. The structure and probable mode of development (secretion from the hypodermis) are described. The basic structure of the “mature” cuticle is an outer three-layered membrane, two cortex layers, a medial layer which in the adult is striated, and two fibril layers. The cuticle is attached to an outer corrugated hypodermal membrane by means of desmosomes on the crests of the corrugations. It is thought that the secretion of the cuticle occurs in the trough regions. The hypodermis has the appearance of a highly active layer with an abundance of ribosomes and mitochondria. The hypodermis is cellular and is not a syncytium. Bacillary cells have been demonstrated for the first time in the lateral hypodermal cords of adult T. spiralis. The body wall muscle is similar in structure to that of other nematodes but an increase in the number of muscle cells per intercordal sector from the first-stage juvenile to the adult is recorded and some doubt is therefore cast on the concept of cell constancy in nematodes.