Fine structure of body surface of Thelazia skrjabini (Nematoda: Spirurida, Thelaziidae).

Thelazia skrjabini (Spirurida, Thelaziidae) is a parasite of cattle that causes ocular infections. Scanning electron microscopy was used to study the surface ultrastructure of adult worms of this nematode. At the anterior end of both sexes, the buccal opening was orbicular. Around the mouth, two circles of cephalic papillae were seen: the inner circle with six papillae and the outer circle with four submedian papillae. At both lateral sides of the head, two amphids were observed. A pair of lateral cervical papillae was present. In the female, the vulva was located at the anterior part of the body and the tail carried an anal pore and two phasmids near the tip. In the male, the tail was blunt without caudal alae and curved ventrally. There were 31 to 38 unpaired preanal papillae, two paired postanal papillae, and two phasmids at the posterior end. The cuticle had fine, scarcely visible transversally striations. At the anterior end of the two cases, one abnormal mass was seen.