A redescription of Cylicocyclus triramosus (Nematoda: Strongyloidea): a parasite of the zebra, Equus burchelli antiquorum.

Cylicocyclus triramosus, a rare species of Cyathostominae from the southern African Burchell's zebra (Equus burchelli antiquorum) is redescribed, and a neotype is proposed. The external leaf-crown of the species consists of 30 elements and the internal leaf-crown numerous small and clear elements. The buccal capsule is cylindrical, oval in cross section, and approximately 3 times as wide as deep. The thin walls of the buccal capsule taper anteriorly from a large ringlike, hoop-shaped thickening around the posterior margin. The dorsal gutter is nipple-shaped. The mouth collar is notched dorsally and ventrally. The dorsal ray of the copulatory bursa is slightly elongate and distinctly set off from the lateral lobes. The branches of the dorsal ray have auxiliary branches. Appendages of the genital cone consist of 2 separated, large, semilunar plates with finger-shaped processes on the margins. The vulva-to-anus distance is greater than the tail length. The species is most similar to Cylicocyclus radiatus. Cylicocyclus triramosus differs from all similar species in the presence of dorsal and ventral notches in its mouth collar. In addition, C. triramosus also has a distinctive form of male genital cone appendage. Cylicocyclus radiatus differs further from C. triramosus in lacking a dorsal gutter and having a more elongate dorsal ray and a female tail nearly equal in length to the vulva-to-anus distance.