This study measured trap induction and trapping on agar disks as affected by juvenile stages (J1, J2, J3, and J4) of the nematode Caenorhabditis elegans and by species of nematode-trapping fungi. Eight species of nematode-trapping fungi belonging to the family Orbiliaceae and producing four kinds of traps were studied: adhesive network-forming Arthrobotrys oligospora, A. vermicola, and A. eudermata, constricting ring-forming Drechslerella brochopaga, and Dr. stenobrocha, adhesive column-forming Dactylellina cionopaga, and adhesive knob-forming Da. ellipsospora, and Da. drechsleri. The number of traps induced generally increased with increasing juvenile stages of C. elegans. The ability to capture the juveniles tended to be similar among isolates that produced the same kind of trap but differed among species that produced different kinds of traps. Trapping by Dr. stenobrocha and Da. cionopaga was correlated with trap number and with juvenile stage. A. oligospora and A. vermicola respectively captured more than 92 and 88% of the J1, J3, and J4 but captured a lower percentage of J2. The knob-producing isolates captured more younger than elder juveniles. Partial correlation analyses demonstrated that the trap induction of the most fungal species positively correlated with the juvenile size and motility, which was juvenile stage dependent. Overall, trap induction and trapping correlated with C. elegans juvenile stage (size and motility) in six species of trapping fungi.

Lectin binding sites on the surface of Meloidogyne incognita Races 1, 2, 3, and 4; M. javanica; M. arenaria Races 1 and 2; and M. hapla Races A and B were determined with lectins conjugated to fluorescein isothiocyanate or colloidal gold. The amphidial exudate, which was demonstrated histochemically to contain carbohydrate, was the principal binding site. Some lectins also bound to the external cuticular surface. Species and race specific binding patterns were observed for both amphidial and cuticular binding sites.

The occurrence and distribution of several lectin binding sites on the outer surfaces of eggs, preparasitic second-stage juveniles (J2), parasitic second-stage juveniles (PJ2), females, and males of two tylenchid nematodes, Anguina tritici and Meloidogyne incognita race 3, were compared. In both species, a greater variety of lectins bound to the eggs than to other life stages; lectin binding to eggs was also more intense than it was to other life stages. Species-specific differences also occurred. More lectins bound to the amphids or amphidial secretions of M. incognita J2 than to the amphids or amphidial secretions of A. tritici J2. Lectins also bound to the amphids or amphidial secretions of adult male and female A. tritici, but binding to the cuticle occurred only at the head and tail and was not consistent in all specimens. Canavalia ensiformis and Ulex europaeus lectins bound specifically to the outer cuticle of M. incognita. Several other lectins bound nonspecifically. Oxidation of the cuticle with periodate under mild conditions, as well as pretreatment of the nematodes with lipase, markedly increased the binding of lectins to the cuticle of A. tritici J2 but not, in most cases, to M. incognita J2 or eggs of either species.

The conidia of the endoparasitic fungus Meria coniospora (Deuteromycetes) had different patterns of adhesion to the cuticles of the several nematode species tested; adhesion in some species was only to the head and tail regions, on others over the entire cuticle, whereas on others there was a complete lack of adhesion. After adhesion, the fungus usually infected the nematode. However, adhesion to third-stage larvae of five animal parasitic nematodes, all of which carry the cast cuticle from the previous molt, did not result in infection. M. coniospora infected animal parasitic nematodes when this protective sheath was removed. Seven preparations of sialic acid (N-acetylneuraminic acid) gave three types of response in adhesion-infection of nematodes:(i) a significant reduction in conidial adhesions;(ii) no interference with adhesion, but a 10-day delay in infection; and (iii) a delay in infection by 2 to 3 days. The current results support previous findings indicating involvement of sialic acids localized on nematode cuticles in recognition of prey by M. coniospora.

Complementary experiments were performed to indicate the presence or absence of sialic acids in axenically cultured Panagrellus redivivus and Caenorhabditis elegans. Competitive displacement experiments with radiolabeled Limax flavus agglutinin demonstrated the presence of sialic acid in nematodes grown in medium which contained liver extract as a growth factor but the absence of sialic acid when heme was substituted for liver extract. This finding suggested that sialic acid present in the liver medium was responsible for conflicting results of other studies. Transmission electron microscopy of thin sections from nematodes labeled with an LFA-ferritin conjugate revealed no label to the surface area of the cephalic chemosensilla. Fluorometric analysis with a modification of the thiobarbituric acid assay was negative for sialic acid. Analyses by gas chromatography-mass spectrometry, sensitive to the high picomole range, were also negative for sialic acid. Taken together the results provide evidence for the absence of sialic acid in P. redivivus and C. elegans using the most sensitive and diagnostic technique currently available.

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.

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.