| dc.description.abstract | The morphology of elaphostrongyline nematodes parasitizing North American
cervids was studied using light and scanning electron microscopy in order to improve
previous descriptions that were based exclusively on light microscopical studies.
Structures including the spicules, gubernaculum, bursa, cephalic region, sensory
structures, and female tails of Parelaphostrongylus tenuis, P. odocoilei, P. andersoni,
and Elaphostrongylus cervi rangiferi are described. The morphology of E. c. rangiferi
as described in this study is similar to previous light microscopical descriptions. The
spicules of all three Parelaphostrongylus spp. were alike but differed from those of E.
c. rangiferi by having a dorsal branch of the spicule shaft in the distal region that
extends to the tip. A membrane spans the area between the branch and the shaft.
The corpus of the gubernaculum of P. odocoilei is not split distally as has been
described by previous authors, but instead has a longitudinal groove in the distal
region. Ventral protuberances associated with the cloaca are present in
Parelaphostrongylus spp. but absent in E. c. rangiferi. Sensory papillae and pores
associated with the cloaca and the bursal rays are described. In dorsal view, the base
of the dorsal ray has a prominent edge of thickened cuticle in P. odocoilei and P.
andersoni, whereas in E. c. rangiferi and P. tenuis it is smooth. The female tails of
Parelaphostrongylus spp. have a papilla-like projection at their tips.
The phylogeny of the Elaphostrongylinae was reconstructed using cladistic
techniques. Morphological characters described in this study provide strong evidence for the monophyly of Parelaphostrongylus. The genus is made up of two clades, one
containing P. odocoilei and P. andersoni, the other being P. tenuis. The biogeography
of the Cervidae of North America in relation to the phylogeny of the
Elaphostrongylinae is discussed. The genus Parelaphostrongylus probably coevolved
with the genus Odocoileus in the Nearctic, while Elaphostrongylus spp. most likely had
a Palearctic origin. | |
