Dr. Murai Éva szerk.: Parasitologia Hungarica 22. (Budapest, 1989)

drical base has a striated structure due to the microfilaments running parallelly. Mlcrotriches cut transversally have an oval or round form (Fig. 3). No surface coat (glycocalyx) is visible. Adult form (T. hydatigena) The structure of the covering tissue of the neck region and of mature parts of the strobila will be described. The neck region observed under a scanning electron microscope possesses a thick system of microthriches (Fig. 4). The individual microthriches consist of a thin base and rounded tips resembling a "bud" or a "bulb". In some places transversal connections are observed between the microthriches. By transmission electron microscopy the microthriches show a similar, mushroom-like appearance with a "trunk", the base of the microthriches and a "cap", their apical part (Fig. 5a). In transversal sections rectangular, triangular or Irregular trapezoid forms are observed, depending on the slant of the section (Fig. 51. The outermost surface is covered by a membrane which is not continuous but has small pores which lend it a riddle-like appearance. The outer plasma membrane covers not only the microthriches but also the areas between them. Immediately under it lies the inner membrane which is rough and of higher electron density. This membrane gets thicker in the area of the cap of the microtriches and is clearly seen in longitudinal sections. The substance filling the heart of the microthriches is comparatively light in colour. In transversal sections its structure is rough, and in longitudinal sections it is striated due to numerous substructures running parallelly. The relief of the mature parts of the strobila differs from the one described for the neck part. The brush border consists of densely situated, slanted microthriches oriented towards the back parts of the strobila (Fig. 6). The microthriches resemble arch-like projections with a wider base and gradually thinning at the end, forming claws. By transmission electron microscopy the microthriches are cylindrical, gradually getting finer at their apical end, their form resembling a spine-like or beak-like ending (Fig. 7). In transversal sections microtrlches are of oval or round shape (Fig. 8). The outer plasmal membrane preserves its porous character, and the inner strongly osmiophllic one reaches the spine-like ending of the microthriches (Fig. 8a). Although the spines are the most electron-dense parts of the microthriches, tubular or lamellar substructures can be observed in them. The heart of the microthrix bodies is electron-microscopically lighter but also striated (Fig. 7a). A three-layered membrane was observed between the spine-like cao and body separating the two parts of the microthriches. The microthriches from all parts of the strobila are covered by a thin veil or coat which is a loose, net-like structure: glycocalyx (Figs 8, 8a). The morphological picture of this filamental cover is uniform along the surface of the whole strobila which varies in thickness (from 0. 5 to 1 urn). DISCUSSION The present study reveals some specificities in the structure of the tegumental surface of the larval and adult forms of T

. hydatigena. The changes observed in the density and form of the microthriches and conseouently in the relief of the surface in general reflect a tendency In their development parallel to the ontogenetic development of the helminth.