Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 2009
Publication Date: March 20, 2010
Citation: Hoberg, E.P., Abrams, A., Pilitt, P.A. 2009. Synlophe structure for species of Longistrongylus (Nematode Trichostrongyloidea), abomasal parasites among ungulates from sub-Saharan Africa, with comparisons to the global ostertagiine fauna. Journal of Parasitology. 95:1468-1478.
Interpretive Summary: Medium stomach worms in ungulates remain economically and ecologically significant pathogens in free-ranging and domestic hosts throughout the world. Dissemination of these parasites coinciding with transport and introduction of various host species across many regions of the world including North America establishes a need for accurate identification of exotic nematodes. Species of Longistrongylus are characteristic medium stomach worms (Ostertagiinae) which reside in the abomasum and infect ungulate hosts endemic to sub-Saharan Africa. Although the 8 species of this genus are reasonably well characterized, there remains limited information about the structure of the synlophe, or system of longitudinal cuticular ridges, typical of these nematodes. The synlophe has been used extensively to distinguish among genera and species, and to provide the basis for unequivocal identification of female nematodes which often have few definitive diagnostic attributes. Species of Longistrongylus each appear to have a characteristic “tapering pattern” laterally in the cervical zone (the region of the nematode body anterior to the esophageal-intestinal junction) which is largely consistent among multiple male and female specimens. 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 male and female specimens. Accurate identification is an cornerstone for understanding patterns of biodiversity and the overall distributions of pathogens that pose threats to an array of food-animals.
The synlophe, or system of longitudinal cuticular ridges characteristic of some trichostrongylid nematodes, is examined in detail for 6 of 8 species in the genus Longistrongylus (Ostertagiinae) that occur in ungulates across sub-Saharan Africa. The synlope 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 of Longistrongylus each appear to have a characteristic tapering pattern laterally in the cervical zone (anterior to the esophageal-intestinal junction) which is largely consistent among multiple male and female specimens. 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 which in part diagnose the genus Longistrongylus.