The ultrastructure of the tegument of Moniliformis dubius (Acanthocephala).

The ultrastructure of the body wall of Moniliformis dubius has been studied in the light and electron microscope. It consists of an apparently syncytial tegument, overlaid by a tenuous cuticle in the form of a finely fibrous extracellular fringe and is backed by a basement membrane and fibrous connective tissue. The tegument contains a framework of fibres, which, distally, is connected to a dense fibrous meshwork separated from the cuticle by two membranes. Within the syncytial tegument are found the usual cytoplasmic organelles: mitochondria (often degenerate in structure), Golgi clusters, small amounts of other smooth membranes, and numerous dense particles (glycogen and perhaps ribosomes). Many mitochondria contain dense particles. Evidence of vacuole formation at the surface of the tegument suggests that pinocytosis plays a part in assimilation.