Ultrastructure and cytochemistry of the tegument of Atriaster heterodus (Platyhelminthes : Monogenea)

The tegument of the polyopisthocotylean monogenean Atriaster heterodus Lebe dev & Parukhin, 1969 was studied using transmission electron microscopy. Th e outer syncytial layer of the tegument is connected to the internal cell b odies by cytoplasmic extensions which interweave between the muscular fibre s. The free surface of the syncytium has projections of the external membra ne which are similar to microvilli. The undulating basal membrane, with num erous narrow elongate projections, is associated with the basal lamina situ ated between the syncytial and muscular layers. The cell bodies and syncyti al layer of the tegument exhibit two types of vesicles, one with fibrous co ntents and one with electron-dense contents; these were analysed using two cytochemical tests, the E-PTA and alcian blue methods, used for the first t ime on monogeneans.