Interbreeding in the Subfamily Ostertagiinae (Nematoda: Trichostrongylidae) of Ruminants

Abstract

The interbreeding of 6 species of ostertagiines was studied in a sheep model. Virgin young females of selected nonpolymorphic strains of Ostertagia ostertagi, Ostertagia leptospicularis, and Teladorsagia circumcincta were mated with various male ostertagiines. Interbreeding was successful between O. ostertagi and Ostertagia lyrata, O. leptospicularis and Ostertagia kolchida, and T. circumcincta and Teladorsagia trifurcata, respectively. Their offspring were fertile and resembled one parent or the other without intermediate forms: each pair is a polymorphic species. Infertile hybrids, intermediate in form, were obtained from interbreeding between O. ostertagi and O. leptospicularis and they remain valid species.