Topography and ultrastructure of the tegument of Aphallus tubarium (Rodolphi, 1819) Poche, 1926 (Digenea: Cryptogonimidae), intestinal parasite of the common Dentex dentex (Linnaeus 1758) from Valinco Gulf.

Abstract

The tegument ultrastructure of the intestinal fluke Aphallus tubarium was studied for the first time with the use of scanning and transmission electron microscopy. New details on morphology were recorded. The ultrastructural study revealed that the tegument of A. tubarium had a syncytial organization with a distal cytoplasm lying over a basal matrix and cytons. The surface of the tegument is covered with pectinate spines arranged quincuncially. As anterior-posterior differences were observed, particular attention was given to spines. Spines decrease in size and density from the anterior part of body to posterior part. Two types of sensory structures were identified, uniciliated and dome-shaped. Type 1 sensory receptors were outgrowths bearing groups of papillae with shorter and rigid apical seta visible on the anterior part of body surface, encircling the worm. Type 2 sensory receptors was dome-shaped papillae devoid of cilia, found mainly around the oral sucker. Diagrams of spines and sensory receptors were made to help in understanding the nature of these structures. Surface morphology may prove to be useful in distinguishing Aphallus spp with other Cryptogonimidae.