Scanning electron microscopic observations on adult Spirocerca lupi (Nematoda: Spirurida, Thelaziidae).

Scanning electron microscopy was used to study the surface ultrastructure of adult worms of Spirocerca lupi. At the anterior end of both sexes, the mouth is hexagonal, without definite lips. Around the mouth, two pairs of submedian cephalic papillae and two lateral amphids are present. There is a pair of lateral cervical papillae. At the anterior end of the body, on the ventral side, an excretory pore is seen. In the female, the vulva is located anteriorly and the tail is blunt, with a pair of subterminal phasmids. The male tail is spiral, with four pairs of preanal papillae, a single large median preanal papilla on the anterior lip of the cloacal aperture, two pairs of postanal papillae, four pairs of tiny papillae near the tip of the tail and two subterminal phasmids. The cuticle shows an abnormal tumour-like mass in two cases.