Synlophe structure for species of Longistrongylus (Nematoda: Trichostrongyloidea), abomasal parasites among ungulates from sub-Saharan Africa, with comparisons to the global ostertagiine fauna.

The synlophe, or system of longitudinal cuticular ridges characteristic of some trichostrongyloid nematodes, is examined in detail for 6 of 8 species in Longistrongylus (Ostertagiinae) that occur in ungulates across sub-Saharan Africa. Among the species of Longistrongylus examined, 5 are characterized by a tapering pattern laterally in the cervical zone (anterior to the esophageal-intestinal junction), which is largely consistent among multiple male and female specimens; in contrast, for Longistrongylus meyeri the lateral pattern is parallel. The synlophe is bilaterally symmetrical, with ridges extending from the base of the cephalic expansion to near the caudal extremity in males and females. Ridges are acutely pointed, with perpendicular orientation and absence of gradient as viewed in transverse section. Species-specific patterns in conjunction with the numbers of ridges may serve to augment an array of diagnostic characters for species of Longistrongylus and contribute to increasingly accurate identification of female specimens. Among 5 of 6 species examined in the current study, the numbers of ridges in males was equal to or exceeded that observed in females, a pattern seen only in Africanastrongylus among the 15 genera of the Ostertagiinae. The differential numbers of ridges in males and females may represent another character among the suite of attributes that in part diagnose the genus Longistrongylus .