Abstract
Surface ultrastructure of strigeid trematode, Cardiocephalis longicollis (Rudolphi, 1819) from herring gulls, Larus argentatus (Pontoppidan, 1763) was investigated with highlighting on its pathogenic effect on intestine of gulls. Scanning electron microscopy showed that the digitiform processes of the holdfast organ, which appeared solid at light level, were pedunculated and formed hollow structure-like suckers and surrounded with longitudinal ridges and ornamented with fine tubercles. Outer surface of the processes was provided with minute needle-like spines. These modifications might explain the tight attachment and penetration of the flukes to the intestinal mucosa of infested gulls. Surface ultrastructure of hind body was smooth with exception of some interrupted longitudinal ridges, minute pores and elongated slits. Hind body was terminated posteriorly with an adhesive disc of the copulatory bursa, which was provided with minute papillae of sensory function around the genital opening. Intestinal histopathology showed that the aggressive invasion of C longicollis to the intestine resulted in formation of numerous fibrotic nodules on the surface of the intestine accompanied with hemorrhagic spots and a severe destruction to the intestinal mucosa which might impair feeding, digestion and absorption processes.