Scanning electron microscopy of Clinostomum metacercaria from Oreochromis niloticus from Assiut, Egypt

Abstract

The topography of the tegument of Clinostomum metacercaria showed variable features according to the different sites of the surface. At the ventral side, the rims of the oral and ventral suckers had minor differences, while their floor showed great variation in topography: the floor of the oral sucker had longitudinal wrinkles with nodule-like structures and their upper margins had minute sensory papillae, while the ventral sucker had a rugose surface possessing some smooth dome-like papillae. The area between the two suckers had a corrugated surface. The post-acetabular region was highly folded with sponge-like margins, while the inner area was smooth. The rest of the body surface had two forms of polygonal units of villi each surrounding one or two sensory papillae. The dorsal side had plenty of pores and apertures: several crescent slits each had nail-like covers distributed marginally at the anterior region; a narrow aperture with a dentate margin was seen at both postero-lateral sides; behind each lay a large aperture with single operculum; and finally there was the excretory pore at the end of the body. Micropores were distributed in many sites of the dorsal side. The surface was like cobblestones at the anterior region of the body, but flattened, smooth, and polygonal-like on most of the median area, and papillated around the excretory pore. The possible function of each structure was discussed.

KEY WORDS: Scanning, topography, Clinostomum, oreochromis, metacercaria.

Egyptian Journal of Botany Vol.5 2003: 70-77