Description, relationships, and host symptoms of Ditylenchus dryadis n.sp. (Nematoda: Tylenchidae) from the Canadian High Arctic, a transitional species of gall-forming parasite attacking Dryas integrifolia M. Vahl

Morphology and symptoms of Ditylenchus dryadis n.sp., a bisexual leaf galling parasite that is similar taxonomically to D. dipsaci and pathogenically to the Anguininae, are described and illustrated. The main differentiating characters for the female are its large, distended postuterine sac, which occupies 75% of the vulva–anus distance and the quadricolumellate crustaformaria; and, for both sexes, six to eight incisures, presence of a conspicuous deirid, a basal esophageal bulb of three cells that does not overlap the intestine, and an acute tail terminus. Disease symptoms are galls of various configurations on the leaves only of Dryas integrifolia M. Vahl, ecologically the most important of the vascular plants from the type locality and a new host record for plant parasitic nematodes. Galls examined on dried leaves were typically red, had diameters of up to 5 mm, and contained from 2 to 60 nematodes with numerous eggs.