Morpho-functional characteristics of the scolex of Wardium chaunense (Cestoda: Aploparaksidae) penetrated into host intestine.

The scoleces of Wardium chaunense penetrated into the intestinal wall of a snipe (Gallinago gallinago) were examined by light and transmission electron microscopy for the first time. Naturally, the scolex is characterised by a shorter length in comparison with when it is removed from the host. Ultrastructural characteristics of the main parts of the scolex, such as suckers, rostellum and rostellar sac are reported. Partial degradation of the radial muscles of the suckers is clearly recognised; this can be the result of a deep penetration of the scolex into the mucosa and subsequent loss of attachment function by suckers. The muscular walls of the rostellum and rostellar sac have a structure of the same type: an outer longitudinal layer of muscles is separated from the inner circular one with a thin basal matrix, which, also, surrounds each muscular fibre of the circular layer. Circular fibres consist of mutually perpendicular myofibrils, connected with the basal matrix by hemidesmosomes. Microtriches, covering the tegument, vary in shape in different regions of the scolex. They are absent on the apical part of the rostellum, and are slightly curved and can be considered as belonging to the fixative type on the suckers. Special sensory endings with a dense central body and without cilia are situated at the distal cytoplasm of the tegument of the suckers. Two glands, having the same syncytial structure, are disposed inside the rostellum and rostellar sac. Erythroid granules produced by the glands are released during an apocrine process into the host-parasite contact zone. Secretions of the cestode tegument in the form of vesicles and bubbles of granular material were also observed. It is suggested that the scolex attachment method of W. chaunense has the tendency of 'anchoring', which is an irreversible attachment used by some cestode parasites of the snipe.