Abstract
In the present study, the fine surface structures of Cystocaulus ocreatus and its worm as well as brood nodules obtained from the lung of Akkaraman sheep are demonstrated by scanning electron and light microscopy. The mouth of the parasite obtained from the worm nodules is located at the anterior tip and encircled by a collar of tissue. The mouth opening appears as three slits conjoined in the shape of a capital case letter Y, creating three lips. The mouth is surrounded by six papillae just behind the collar. The anterior end was similar in both sexes and covered by numerous wrinkles. Female parasite has a bell-shaped pro-vagina. The posterior end of the female parasite was sharply pointed. The male parasite has a bursa. In the worm nodule, curled parasites were enclosed by a capsula and no eggs and larvae of the parasite were observed. In the brood nodule, heavily affected alveoli and bronchioles contained excessive amounts of larvae and eggs.