title: Morphological and Molecular Characterization ofGracilacus wuaen. sp. (Nematoda: Criconematoidea) Associated with Cow Parsnip (Heracleum maximum) in Ontario, Canada.
abstract: Gracilacus wuaen. sp. from soil associated with cow parsnip in Ontario, Canada is described and illustrated. Morphologically, females have a long stylet ranging from 80 to 93 µm long, the lip region not offset from the body contour, without lateral lips but with large and flat submedian lobes, the mouth opening slit-like elongated laterally and surrounded by lateral flaps, the excretory pore is anterior to the knobs of the stylet; males without stylet and the pharynx degenerated. The fourth-stage juveniles lack a stylet, the pharynx degenerated, and can be differentiated into preadult females and males based on the position of the genital primordia. The third-stage juveniles are similar to females but smaller. Phylogenetic studies using the rDNA small subunit 18S, large subunit 28S D2/D3, and internal transcribed spacer (ITS) sequences collectively provide evidence of a grouping with otherGracilacusand some species ofParatylenchuswith stylet length of females longer than 41 µm deposited in GenBank.
authors.affiliation: Ottawa Research and Development Center, Agriculture and Agri-Food Canada, Ottawa, ON K1A 0C6, Canada.
authors.forename: Qing
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Nematode Assay Section, Agronomic Division, North Carolina Department of Agriculture & Consumer Services, Raleigh, NC 27607-6465.
authors.forename: Weimin
authors.initials: W
authors.lastname: Ye
authors.affiliation: Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583-0722.
authors.forename: Tom
authors.initials: T
authors.lastname: Powers
keywords: Gracilacus; Paratylenchus; molecular; morphology; morphometric; new species; taxonomy