Scanning electron microscopic observations on the tegumental surfaces of two rumen flukes (Trematoda: Paramphistomata).

The surface microtopography of Calicophoron papillosum (Stiles & Goldberger) and C. calicophorum (Fischoeder), inhabiting the rumen of sheep, has been studied by SEM. In C. papillosum, conspicuous transverse ridges encircle the mid-body, gradually lessening dorsally towards the posterior end. The general body surface is aspinose and smooth except for minute bead-like tubercles in the circumoral area. Two types of putative sensory structures-domed aciliate papillae and tegumental pits-are present. Their characteristic aggregation in certain regions and their distribution in other parts of the body is described. A unique pattern of ridges, confined only to the base of the genital papilla and the genital atrium, has been observed. In C. calicophorum, tegumental folds encircle the body, these are more numerous near the anterior end and fewer posteriorly. The oral area has numerous concentric folds with domed aciliate papillae; between or on the papillae are tegumental elevated pits from the centre of which a knob-like structure protrudes. These sensory structures occur to a lesser extent in the acetabular area.