M.B. Lancaster’s research while affiliated with Surrey Place Centre and other places

The systematics of the Ostertagiinae is unsettled with no agreement on how many genera and species are present in cattle and sheep. Ten species of Ostertagiinae are commonly parasitic in cattle and sheep. The males can be identified on the basis of differences in morphology of spicules and genital cones but the females of most species cannot be identified. The species-level systematics have been complicated by the proposal that the ten species are polymorphs of only five species. The systematics at genus level has been complicated by the use of numerous genera for the ten species, at present most commonly Ostertagia, Teladorsagia and Marshallagia. This report (1) describes the current knowledge of the systematics and (2) provides diagnoses of the genera recommended for the ten species. The morphology of the ten species was studied to determine whether characteristics could be found to identify females or to further differentiate the males. Characters studied included the system of longitudinal and surface cuticular ridges (synlophe), the internal morphology of the esophagus and the orientation of rays of the copulatory bursa. The study of species morphology resulted in additional support for the polymorphism proposal. All minor species were found to be identical to their major species in characteristics of the synlophe, esophagus and rays of the copulatory bursa.