Stereoscan studies of two species of the genus Oesophagostomum [Nematoda, Chabertiidae]

The fine surface topography of Oesophagostomum columbianum and O. aspersum, the predominant nematode species of goats in India, has been studied by means of SEM. In O. columbianum the anterior end is bent like a hook; the cephalic vesicle is marked behind by a groove; the lateral alae are present throughout the anterior extremity thereby providing a dorsal curvature to the body; the external corona radiata is seen to consist of 20 elements; and the spicules are long and seen as twisted upon each other. In O. aspersion the external corona radiata comprises 12 elements; the vulva and the anus lie behind a constriction at the posterior extremity and quite close to one another. Characters, such as the amphids, cephalic papillae, prebursal papillae, etc., are elucidated for both species.