Differentiation of Coronocyclus sagittatus and Coronocyclus coronatus (Nematoda : Cyathostominea) of horses

An increased interest worldwide in small strongyles of horses has prompted a revision of the systematics in order to support research on improving ant iparasitic chemotherapy. biocontrol. and other management practices. A 1997 international workshop developed a revised list of recommended names for 5 1 recognized species of Cyathostominea and indicated problems in the differ entation of some species, including Coronocyclus coronatus (Looss, 1900) an d C, sagittatus (Kotlan, 1920). These morphologically similar species are m embers of Coronocyclus Hartwich. 1986, a genus with prominent and sclcrotiz ed external leaf crown supports that are separated from the buccal capsule. The two species can be distinguished from one another by differences in th e shape of the buccal capsule, in the shape of the buccal capsule wall in o ptical section. in the point of insertion of elements of the internal leaf crown , and in the dorsal ray of the male. Drawings and photomicrographs ar e presented that illustrate the characteristics useful for differentiating C. coronatus and C. sagittatus.