ULTRASTRUCTURE OF THE PHARYNGEAL CUTICLE AND LECTIN LABELING WITH WHEAT-GERM AGGLUTININ-GOLD CONJUGATE INDICATING CHITIN IN THE PHARYNGEAL CUTICLE OF OESOPHAGOSTOMUM-DENTATUM (STRONGYLIDA, NEMATODA)

The ultrastructure of the pharynx of the first juvenile stage and of a dult Oesophagostomum dentatum (Nematoda, Strongylida) is investigated by TEM. Additional light microscopical and SEM data are presented for the anterior alimentary canal of all life-history stages and for adult O. quadrispinulatum. Ultrathin sections of adult and the first juveni le stage O. dentatum are labelled with the lectin wheat germ agglutini n coupled to colloidal gold. The pharyngeal cuticle consists of a tril aminate epicuticle and an amorphous basal layer, which also exhibits i ndividual fibres in adult worms. The pharyngeal cells of the first juv enile stage an already arranged as in the adult worm. In comparison wi th data for additional nematodes taken from the literature, a trilamin ate epicuticle and an amorphous basal layer are postulated for the pha rynx in the ground pattern of the Nematoda. Lectin-gold labelling reve als a strong binding to the pharyngeal cuticle of O. dentatum. Competi tive inhibition experiments with N-acetyl-D-glucosamine and triacetylc hitotriose, as well as treatment with chitinase, neuraminidase and sul phuric acid, indicate that the pharyngeal cuticle contains chitin. Thi s finding is supported by staining of the pharyngeal cuticle by the fl uorescent brightener calcofluor white in cryosections of O. dentatum. The occurrence of chitin is interpreted as an original character of th e Nematoda. (C) 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.