The fine structure of the body-wall in a free-living nematode, Euchromadora vulgaris

Abstract

ABSTRACT The body-wall of adult Euchromadora vulgaris is composed of the 3 layers common to all nematodes, the cuticle, epidermis, and muscle cells. The cuticle is composed of 4 layers, a thin membrane resolvable only by the electron microscope, and 3 layers which can be observed in the light microscope. Histochemical tests show that the cuticle is predominantly protein and contains collagen. Of the 3 main layers of the cuticle, the outermost is about 0.4 μ thick and it is penetrated at regular intervals by grooves which divide the cuticle into annuli. This layer has several features in common with the external cortical layer of the cuticle in Ascaris lumbricoides; it is hardened by disulphide bonds and possibly quinone tanning, and is resistant to collagenase. The middle layer is about 1 to 1.3 μ thick and is formed from a series of overlapping plates. The rod-like bodies of de Man are located in this layer and are hollow. Internally, the cuticle is bounded by a basal lamella about 02 μ thick. The epidermis is thickened to form 4 chords and is composed of a large number of cells, which contain filamentous mitochondria with many cristae, granules of glycogen, and, in the pharyngeal region, pigment spots. The fibrillar zone of the muscle cell contains myofilaments of two types, large filaments 20 to 25 mμ in diameter, which are surrounded by smaller filaments 5 to 7 mμ in diameter. There are filamentous mitochondria, glycogen and a nucleus in the protoplasmic bulb. Covering the muscle cell is a thin membrane, the sarcolemma, which is infolded at regular intervals between groups of myofilaments. The sarcolemma is fused with the basal cuticular layer at both ends of each muscle cell.