Caudal Polymorphism and Cephalic Morphology among First-Stage Larvae of Parelaphostrongylus odocoilei (Protostrongylidae: Elaphostrongylinae) in Dall’s Sheep from the Mackenzie Mountains, Canada

• Main Authors: Hoberg, Eric P., Jenkins, Emily J., Rosenthal, Benjamin, Wong, Mayee, Erbe, Eric F., Kutz, Susan J., Polley, Lydden
• Format: Text
• Language: unknown
• Published: DigitalCommons@University of Nebraska - Lincoln 2005
• Subjects: Parasitology; Terrestrial and Aquatic Ecology; Canada; Mackenzie mountains
• Online Access: https://digitalcommons.unl.edu/parasitologyfacpubs/664; https://digitalcommons.unl.edu/context/parasitologyfacpubs/article/1674/viewcontent/Hoberg_2005_JP_Caudal_Polymorphism_and_Cephalic_Morphology_among_First_Stage_Larvae_of_Parelaphostrongylus_odocoilei.pdf

We demonstrate polymorphism in the structure of the tail among first-stage larvae of Parelaphostrongylus odocoilei (Protostrongylidae). Two distinct larvae, both with a characteristic dorsal spine, include (1) a morphotype with a kinked conical tail marked by three distinct transverse folds or joints and a symmetrical terminal tail spike and (2) a morphotype with a digitate terminal region lacking folds or joints and with an asymmetrical, subterminal tail spike. These divergent larval forms had been postulated as perhaps representing distinct species of elaphostrongyline nematodes. Application of a multilocus approach using ITS-2 sequences from the nuclear genome and COX-II sequences from the mitochondrial genome confirmed the identity of these larvae as P. odocoilei. Additionally, based on scanning electron microscopy (low-temperature field emission), the cephalic region of these larvae consisted of a cuticular triradiate stoma surrounded by six single circumoral papillae of the inner circle, ten papillae of the outer circle (four paired and two single), and two lateral amphids. Ours is the first demonstration of structural polymorphism among larval conspecifics in the Metastrongyloidea and Strongylida. The basis for this polymorphism remains undetermined, but such phenomena, if discovered to be more widespread, may contribute to continued confusion in discriminating among first-stage larvae for species, genera, and subfamilies within Protostrongylidae.