Hamulonema gen. nov. for Teladorsagia hamata and Ostertagia kenyensis in the Ostertagiinae Fauna (Nematoda: Trichostrongyloidea) from African Ungulates

Hamulonema gen. nov. is proposed for Teladorsagia hamata and Ostertagia kenyensis in the ostertagiine nematode fauna found in artiodactyl hosts from Africa. Monomorphic species representing this genus are characterized by a bilaterally symmetrical and parallel synlophe in males and females, a 2-2-1 bursal formula, an accessory bursal membrane that is strongly cuticularized and reduced, a strongly reduced dorsal lobe and ray, and robust spicules with a simple, weakly pointed, ventral process, and curved, hooklike dorsal process. Species referred to Hamulonema nov. gen. are immediately distinguished from those of Camelostrongylus, Longistrongylus, Marshallagia, Orloffia, Ostertagia, and Pseudomarshallagia in which the bursal formula is 2-1-2 in males. Hamulonema nov. gen. is distinguished from those genera having a 2-2-1 bursa, including Africanastrongylus, Cervicaprastrongylus, Hyostrongylus, Mazamastrongylus, Sarwaria, Spiculopteragia, and Teladorsagia by the structure of the synlophe, bursa, genital cone, ‘‘0’’ and ‘‘7’’ papillae, dorsal lobe, and spicules in specific instances. In the global fauna, 4 of 14 ostertagiine genera are endemic to Africa. African genera may represent morphologically divergent and discrete or historically isolated lineages reflecting a pattern of geographic and host colonization as a driver for diversification since the Miocene. Abomasal nematodes (Ostertagiinae: Trichostrongyloidea) currently include 13 genera in the global fauna (Hoberg and Abrams, 2007; Hoberg et al., 2008). Morphologically, 2 distinct groups are recognized based on the structure and relative positions of rays that support the copulatory bursa of males (Gibbons and Khalil, 1982a; Durette-Desset, 1983; Jansen, 1989; Hoberg and Lichtenfels, 1994; Durette-Desset et al., 1999). Among ostertagiines, species of 6 genera are characterized by a 2-1-2 bursal formula, i.e., Camelostrongylus Orloff, 1933, Longistrongylus LeRoux, 1931, Marshallagia (Orloff, 1933), Orloffia Dróżdż, 1965, Ostertagia Ransom, 1907, and Pseudomarshallagia (Roetti, 1941). Alternatively, a 2-2-1 pattern is typical among species of 7 genera, i.e., Africanastrongylus Hoberg, Abrams, and Ezenwa, 2008, Cervicaprastrongylus Gibbons and Khalil, 1982, Hyostrongylus Hall, 1921, Mazamastrongylus Cameron, 1935, Sarwaria Dróżdż, 1965, Spiculopteragia (Orloff, 1933), and Teladorsagia Andreeva and Satubaldin, 1954. Among the fauna of medium stomach worms referred to the Ostertagiinae endemic to Africa, 2 species are regarded as having uncertain affinities. The problematic nature of generic-level identity for Teladorsagia hamata (Mönnig, 1932) and Ostertagia kenyensis Gibbons and Khalil, 1982, was highlighted during studies that established Africanastrongylus among artiodactyl hosts (Hoberg et al., 2008). Gibbons and Khalil (1980) recognized the structural similarity of these nematodes, both with a 2-2-1 bursal formula, and distinguished specimens of O. kenyensis from those of T. hamata based in part on the configuration of the dorsal process of the spicules, which were considered to lack a prominent hooklike structure in the former species. Ostertagia kenyensis was originally described based on specimens in Damara Dik Dik (Madaqua kirkii Günther) and Grant’s gazelle (Gazella granti Brooke) from Kenya (Gibbons and Khalil, 1980), but has not been found subsequently (Hoberg et al., 2008). Teladorsagia hamata was based on specimens in springbok (Antidorcas marsupialis Zimmerman) and was later Received 6 July 2007; revised 24 November 2007; accepted 26 November 2007. found in Bontebok (Damaliscus pygargus Pallas) from South Africa (Mönnig, 1932; Hoberg et al., 2008). The latter nematode species, originally described in Ostertagia Ransom, 1907, was later transferred to Spiculopteragia by Travassos (1937), to Apteragia Jansen, 1958 by Jansen (1958), and most recently to Teladorsagia by Durette-Desset (1989). In establishing Africanastrongylus, we identified structural inconsistencies for placement of either T. hamata or O. kenyensis among any known genera of the Ostertagiinae, noted details concerning morphology, and outlined a preliminary proposal to designate a new genus for these species (Hoberg et al., 2008). Meristic data and general comparisons for these species, particularly with respect to comparisons with Africanastrongylus buceros Hoberg, Abrams and Ezenwa, 2008 have been presented previously (Hoberg et al., 2008). In the context of the current study, we now expand on our proposal to resolve generic-level taxonomy for these species and provide comparative morphological criteria for the diagnosis of a new genus in the subfamily. MATERIALS AND METHODS