ULTRASTRUCTURE AND DEVELOPMENT OF THE BODY CUBICLE OF OESOPHAGOSTOMUM-DENTATUM (STRONGYLIDA, NEMATODA)

The ultrastructure, development, and morphogenesis of the body cuticle of adult and juvenile Oesophagostomum dentatum (Strongylida, Nematoda ) were investigated by light microscopy, scanning electron microscopy, and transmission electron microscopy. The cuticle of the first 3 juve nile stages consists of a trilaminate epicuticle, an amorphous layer, and a radially striated layer. In the last juvenile stage and the adul t worm, the radially striated layer is replaced by a fibrous layer wit h 3 sublayers of giant fibers and a basal amorphous layer. The new for ming cuticle of the 3rd juvenile stage exhibits the epicuticle and amo rphous material and, at a later time, the epicuticle and the radially striated layer; finally, amorphous material appears between these laye rs. Our finding of a structural change in the cuticular morphology bet ween the 3rd and 4th juvenile stage harmonizes with earlier reports ab out the Strongylida. Such a change occurs at different ontogenetic sta ges or seems to be missing in other nematodes. Morphogenetic events su ch as the formation of the radial striation layer from amorphous precu rsor material agrees with previous observations on strongylids.