First SEM observations on adult Habronema microstoma (Spirurida: Habronematidae), a parasite of the horse.

Habronema microstoma (Spirurida: Habronematidae) is found in the stomach of equines and uses the stable fly as its intermediate host. This nematode causes pathogenic effects in the stomach wall, skin and eye of the host. The present study reports the morphological features of adult worms, using scanning electron microscopy (SEM). The worms had two bilobed lateral lips surrounding the mouth. The buccal vestibule was markedly thickened, and two tridentate teeth were observed. Around the mouth, four sub-median cephalic papillae and two amphids were seen. A pair of lateral cervical papillae was present. There was only one lateral ala in both sexes. In the female, the vulva was opened in the middle of the body. In the male, there were wide caudal alae, and the spicules were unequal. At the posterior end of the male, four pairs of stalked pre-cloacal papillae, a single lateral pre-cloacal papilla, two pairs of post-cloacal papillae and a cluster of small papillae were present.