Studies on North American Helminths of the Genus Capillaria Zeder, 1800 (Nematoda): II. Additional Capillarids from Mammals with Keys to the North American Mammalian Species

Abstract

As previously remarked by the writer in Part I of this study the worms of the genus Capillaria Zeder, 1800, do not show a marked degree of host specificity. Further evidence in favor of this view is afforded by the fact that C. americana n. sp., described in this paper, has been found in four different species of rodents. C. muris-sylvatici (Diesing, 1851) evidently also occurs in a variety of rodent hosts. Elton, Ford, and Baker (1931) in a study of the parasites of various rodent populations in England failed to find this worm in Microtus although these workers found it in other rodents. Conversely, the writer has found it only in material from Microtus in North America although large collections of parasites from a considerable number of different native rodents have been available for study. It seems probable that food habits are the chief factor determining the acquisition of infections with this species by rodents. Description or discussion of five species of Capillaria from North American mammals follows: Capillaria muris-sylvatici (Diesing, 1851) (Plate II, Figs. 10-13) Worms of this species were recovered from the small intestine of the vole, Microtus p. pennsylvanicus, examined at Madison, Wisconsin. No previous record from this host nor from any North American host has been found in a search of the literature. Since the worms show some features not recorded by other workers, a description of this material seems warranted. Description: Lateral bacillary lines visible. Mouth simple. Cuticle striated transversely. Female: 13.4 to 15.1 mm long; maximum width in posterior region 70 to 75 t. Termination of esophagus 3 mm from anterior end. Vulva just posterior to termination of esophagus, 3 to 3.2 mm from anterior end, with cuticular vulvar flap projecting from region of anterior labium. A discoid cuticular projection is located anterior to vulvar flap at level of esophageal termination. Vulva divides body 1: 3.5 to 1: 3.7. Ova 47 to 60 . long by 24 to 26 . wide; inner shell bends to form collar at each end; outer shell smooth. Anus slightly subterminal. Male: 9.1 to 10.8 mm long; maximum width 45 to 47 j. Termination of esophagus 2.7 to 2.9 mm from anterior end. Lateral caudal alae present, about 70 . long. Spicule 204 to 225 & long by 11 to 13 . wide. Spicule sheath without spines or transverse striations. Everted spicule sheath divided into four portions: Distal portion delicate, membranous, usually wrinkled; subdistal portion bulblike, muscular; proximal portion bulblike with rugose markings on lateral aspect; proximal and subdistal portions joined by short wrinkled tubular projection of proximal bulb. Cuticular bursa supported by pair of bifid papillae. Cloaca subterminal. Termination of esophagus divides body about 1:2.7.