Abstract
Gracilacus wuae n. 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 other Gracilacus and some species of Paratylenchus with stylet length of females longer than 41 µm deposited in GenBank.
Highlights
Gracilacus wuae n. sp. from soil associated with cow parsnip in Ontario, Canada is described and illustrated
The genus Gracilacus was established by Raski (1962) to differentiate species of Paratylenchus Micoletzky, 1922, based on primarily stylet length and secondarily on body shape and the position of the excretory pore in females
Geraert (1965) divided Paratylenchus sensu lato that includes Gracilacus into groups based on the stylet length and the V-position and recently Ghaderi et al (2014) expanded it by dividing the genus into groups based on stylet length, lateral fields, and advulval flaps
Summary
Nematode samples: Soil samples associated with wild parsnip were collected in Kanata, west of Ottawa, Ontario, Canada, with latitude 45818943.330N and longitude 75855954.080W. The nematodes were extracted with the Baermann funnel method. Extracted nematodes were processed for both morphological and molecular studies. Morphological study: The method used was as described previously (Yu et al, 2014). The nematodes were all fixed in TAF and mounted in dehydrated glycerin on slides for morphological studies. Specimens were examined using a Leica DM5500 B compound microscope (Wetzlar, Germany) using differential interference contrast and pictures were taken with a Leica. Measurements were made using a Leica micro application system on the images. Scanning electron microscope (SEM) pictures were taken with a FEI Quanta 600 SEM
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