Taxonomy, hosts, and geographic distribution of the Setaria (Nematoda: Filarioidea) in the United States and Canada.

Three species of Setaria Viborg, 1795, nematodes of the peritoneal cavity, were found among 439 specimens collected from 12 species of ungulates in the United States and Canada. Setaria equina (Abildgaard, 1789) was found among specimens from horses (Equus caballus), mules (E. asinus X E. caballus), a burro (E. asinus), and a cow (Bos taurus); Setaria labiatopapillosa (Perroncito, 1882) from cattle (Bos taurus), antelope (Antilocapra americana), bison (Bison bison), moose (Alces alces), a deer (Odocoileus hemionus), a bighorn sheep (Ovis canadensis), a caribou (Rangifer caribou), and a horse; and Setaria yehi Desset, 1966, from deer (Odocoileus hemionus and 0. virginianus), caribou (Rangifer caribou and R. arcticus), and bison. Nomenclatural problems involving S. labiatopapillosa and S. yehi are discussed and definitive conclusions are given. Information is given for all three species on geographic distribution, morphology, and intraspecific variation. A key with comparative illustrations is furnished for the easy identification of the worms. Although the literature on Setaria Viborg, 1795, is voluminous, very little concise information has been published on the species of North America, their hosts, and geographic distribution. A considerable amount of the world's literature is nomenclatural or descriptive, but largely with poor illustrations that are either inaccurate or too inadequate for practical use. Because the first few species proposed were not adequately described and their type specimens are unavailable, there exists considerable confusion relating to the application of their names. Recently, two authors (Yeh, 1959; Desset, 1966) summarized the literature and attempted to resolve the confusion about the world's species. While they solve some problems, they also create others. The present report gives new information on North American species, with comparative illustrations and a key for their easy determination. The specimens studied were obtained from the collection at our laboratory or kindly loaned to us by J. R. Adams, University of British Columbia; H. J. Griffiths, University of Minnesota; and K. A. Neiland, Alaskan Department of Fish and Game. It is unknown how the specimens were killed and preserved, but all those from the collection were stored in a solution of 92 parts 70% ethyl alcohol, 3 parts formalin, and 5 parts glycerine. All specimens were cleared in phenol alcohol or lacto-phenol Received for publication 22 October 1968. for study, with the exception of a few which were stained for us by a colleague, F. Stringfellow. All illustrations were made with the aid of a camera lucida. General morphology of the species studied Mouth cavity shallow with sclerotized walls. Mouth aperture surrounded on surface of head by sclerotized peribuccal crown bearing a dorsal and a ventral elevation. Body laterally flattened posterior to peribuccal crown, giving anterior end "shoulders" distinctly visible from dorsal or ventral aspects. Amphid laterally located to peribuccal crown at convex curvature of each shoulder. Two papillae situated submedially in each quadrant. Four papillae, each having a short, slender spine, located nearer peribuccal crown than other four. Conformation of peribuccal crown and shape of mouth from en face aspect vary between species (Figs. 1-15). Cervical papillae present, usually n t situated directly opposite one another. Muscle cells numerous, polymyarian, with fibers parallel and perpendicular to hypodermis, coelomyarian (Figs. 30-33). Female and male, around 90 and 45 mm long, respectively. Similar in shape, usually found with tails coiled. Distally, female curved dorsad, male curved ventrad. Gravid female contains microfilariae, released through muscular ovejector leading to vulval opening in cervical region (Fig. 30). Female tail with terminal knob that may or may not have protuberances. Caudal appendages paired on both sexes, phasmids situated just anterior to them. Spicules dissimilar, left spicule approximately three times length of right spicule. Right spicule short, stout, and complex distally. Left spicule long, slender, and complex with loops near middle or distal fourth where shaft turns ventromedially, ending in a sheath. Terminally, male body smooth and round. Caudal papillae