A study of the fine structure of Caenorhabditis briggsae revealed several features not previously described in free-living nematodes. These were: chambered walls of the stoma, zonula adherens in the esophagus, daedaloid folds in the inner surface of the uterus and openings in the terminal web of the intestinal epithelium. Other structures observed in these studies were similar to those described from other free-living nematodes.

The specific gravity of old Caenorhabditis briggsae was shown to be greater than that of young nematodes. The possible explanations for this age-associated change are discussed.

The fine structure of the esophagus of Pratylenchus penetrans is described. The gland lobe is syncytial and contains two types of nuclei: three large nuclei with little chromatin, and more numerous smaller nuclei with large amounts of chromatin. Some of the smaller nuclei are associated only with glandular tissue, whereas others are part of nerve ceils within the esophagus. Clusters of free ribosomes, rough endoplasmic reticulum, and numerous mitochondria occur in the lobe region where the secretory granules are formed. No Golgi bodies were observed. On the basis of these observations, possible differences in the mechanism of secretory granule formation between plant-parasitic nematodes are discussed. Several other minor differences between the fine structure of other plant-parasitic nematodes previously examined and that of P. penetrans are also noted.

Negative charges on the outer cuticular surface of Meloidogyne javanica females were visualized with electron microscope labelling techniques. Evidence is presented that the electronegative charge is not borne on neuraminic acid. Ruthenium red staining indicated acid mucopolysaccharides on the outer surface. A surface coat, or glycocalyx, external to the outer cuticle membrane was demonstrated.

Stage-specific differences in wheat germ agglutinin (WGA) binding saccharides were demonstrated between the surfaces of the eggs, L1 larvae, young aduhs, and old adults of Caenorhabditis elegans. The WGA binding was to n-acetylglucosamine groups but not to terminally linked n-acetylneuraminic acids. An age-related decrease in WGA binding occurred in adults, supporting previous findings of a decrease in net negative cuticle surface charge during aging.

The location of carbohydrate moieties on the outer cuticle of Xiphinema index was examined by electron microcopy using several different reagents: a) The periodic acid-thiosemicarbazide-silver proteinate reaction was used as a general stain for carbohydrates. In sectioned material it stained the canal system and deeper layers of the cuticle as well as the outer surface, b) Cationized ferritin at pH 2.5, which identifies carboxyl and sulfate groups, was used to identify sialic acid residues and also labelled parts of the canal system, c) Ferritin-goat anti rabbit IgG coupled to a DNP ligand was used to label either sialyl or galactosyl/N-acetyl-D-galactosaminyl residues, d) Ferritin hydrazide, a new reagent, was used for the ultrastructural localization of glyco-conjugates. Reagents c)(with appropriate antisera) and d) were applied only to the outer surfaces of the cuticle; they showed that sialic acid residues were concentrated mainly on the outer body wall of the head, the lips, oral opening, amphid apertures, and outer surface of protruded odontostyles. Ferritin distribution was not altered by pretreatment with neurantinidase. Galactose oxidase treatments revealed galactose/N-acetyl-D-galactosamine residues along the entire body wall. These results confirmed earlier findings obtained by fluorescence microscopy.

Utilizing a Concanavalin A (Con A)-hemocyanin conjugate, the majority of cuticular Con A binding sites were shown to be localized on the head region of Caenorhabclitis elegans and Meloidogyne incognita. Secretions which apparently emanated from the amphids and inner labial papillae did not label.

Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus.