A detailed account is given about the mode of attachment and histopathological effects of Macrogyrodactylus clarii Gussev, 1961, a viviparous monogenean from the gills of the catfish Clarias gariepinus. Most parasites attach their haptors to the proximal region of the gill filament (primary gill lamellae), while few specimens were seen attached to the distal region. Attachment of the haptor was achieved mainly by the blade of the hamuli, but no evidence was found indicating the participation of marginal hooklets in the attachment. The hamuli of M. clarii penetrate into the interlamellar epithelium of the gill tissue. Some evidences were found to indicate that M. clarii may also utilize suction force during haptoral attachment. The pathological effects of M. clarii are manifested by breakdown of the coating epithelium, necrosis of the epithelial cells, vacuolations inside and outside the host cells, fusion of the gill lamellae, rupture of blood capillaries, infiltration of erythrocytes and degeneration and fibrosis of the interlamellar epithelium. The host response includes the appearance of lymphocytes, mucoid secretions and hyperplasia of the tissue at the site of attachment.
The aim of present study was to determine in vitro susceptibility of the yellow mealworm larvae (Tenebrio molitor, Coleoptera: Tenebrionidae) on some environmental isolates of Bacillus thuringiensis and define the degree of change in the midgut epithelial cells of T. molitor larvae. A study of ultrastructural changes in the midgut of the yellow mealworm larvae treated with B. thuringiensis spores and crystals mixture was carried out. Under laboratory conditions four B. thuringiensis environmental isolates were tested for their insecticidal activity against T. molitor larvae. The tested insects pests showed little susceptibility to bacterial suspensions of spores and crystals (13.3%). Despite the relative pathogenicity the microscopic observation of structure of epithelium cells of T. molitor showed changes in the midgut of the treated larvae.