Comparative morphology of Ostertagia mossi and Ostertagia dikmansi (trichostrongylidae) from Odocoileus virginianus and comments on other Ostertagia spp. from the Cervidae

Abstract

The synlophes of Ostertagia mossi Dikmans, 1931 and O. dikmansi Becklund &Walker, 1968 were found to be identical supporting recognition of these as the major and minor morphotypes, respectively, of a putative species pair within the Ostertagiinae. The cervical synlophe included three narrowly spaced, continuous, parallel ridges laterally and three parallel but more widely spaced ridges in the dorsal and ventral fields (Type II and Type A patterns, respectively). The disposition of the synlophe in conjunction with a long oesophageo-intestinal valve, and attributes of the genital cone and spicules are characteristics shared among other Ostertagia spp. from cervids in the Holarctic region that allow recognition of a species group morphologically distinct from the Ostertagiinae of domestic ruminants. The morphological similarity of O. mossi/O, dikmansi, O. leptospicularis Assadov, 1953/O. kolchida Popova, 1937 and O. gruehneri Skrjabin, 1929/O. arctica Mitzkewitsch, 1929 is substantial, but these species can be differentiated by small but constant differences in the synlophe and genital complex of males; females cannot be easily distinguished. The morphological similarity of this cryptic complex of species and their relatively restricted distribution among cervids suggests a coevolutionary history for hosts and parasites in the Holarctic region.

Gastrointestinal Strongyles in Wild Ruminants

“…The proposal for polymorphism has been corroborated based on morphological, biochemical, and molecular grounds (for review see Lichtenfels et al 1997). Consistent with the hypothesis for polymorphism in males, the number of valid genera probably will not exceed nine (see Dr6zdz 1995), but definitive resolution is dependent on phylogenetic studies of this group now in progress (Hoberg et al 1993a;Hoberg and Lichtenfels 1994).…”

“…Morphologically, O. gruehneri is most similar to o. leptospicularis and o. mossi, from which it can be distinguished based on the structure of the genital cone and spicules (Lichtenfels et al 1990;Hoberg et al 1993b;. Disease associated with infections of this species has not been observed.…”

“…Only recently has this species been reported in North America, with records being from cattle or caribou maintained in a captive herd (Rickard and Zimmerman 1986;Fruetel and Lankester 1989;Mulrooney et al 1991). Records from wild cervids in North America are limited to mule deer and elk, but the parasite is considered to have an historically broader geographic distribution, particularly in the western United States (Hoberg et al 1993b;Van Baren et al 1996). The significance of o. leptospicularis is in its reported pathogenicity in cervids.…”

Evaluation of Some Vulval Appendages in Nematode Taxonomy

“…Vulval flaps also are found among other species and genera of the Ostertagiinae, including other species of Ostertagia Ransom, 1907 (Fig. 6) and species of Spiculoptertagia (Orloff, 1933), Mazamastrongylus Cameron, 1935, and Teladorsagia Andreeva and Satubaldin, 1954(Hoberg et al, 1993b. Among Haemonchinae, the putative sister-group of Ostertagiinae Durette-Desset et al, 1999), a considerable amount of body wall occurs in the flaps characteristic of Haemonchus contortus (Rudolphi, 1802), H. placei (Place, 1893), and H. similis Travassos, 1914 (e.g., Das and Whitlock, 1960;Gibbons, 1979;Lichtenfels et al, 1994).…”

“…Sections through the vulval region of these nematodes reveal 3 distinct types of structures (Hoberg et al, 1993b). The first includes consistent, symmetrical, lateral cuticular ''fans'' internally supported by hypertrophied struts, and arising from specific regions within the lateral field.…”