Bursaphelenchus fagi sp. n. (Nematoda: Parasitaphelenchidae), an insect-pathogenic nematode in the Malpighian tubules of the bark beetle, Taphrorychus bicolor (Herbst.) (Coleoptera: Curculionidae, Scolytinae), in European beech, Fagus silvatica L.

Abstract

Bursaphelenchus fagisp. n. is described from the bark of European beech,Fagus silvatica. All propagative stages of the nematode are numerous in larval galleries of the beech bark beetle,Taphrorychus bicolor, while dauer juveniles aggregate in Malpighian tubules of adult beetles. The new species is characterised by the body length of 871 (763-1110) μm in female and 852 (718-992) μm in male, very slender body (a = 56.8 (50.4-67.1) and 64.5 (56.5-73.8) in female and male, respectively), and spicules 15.2 (14.0-17.0) μm long. The extended anterior vulval lip in female, lateral fields with four incisures, and number (7) and arrangement of male caudal papillae may indicate thatB. fagisp. n. is closely related to thexylophilusgroup. It differs from this group by the relatively small, claw-like spicules with narrow capitulum, indistinct condylus in almost continuous line with dorsal lamina, and lack of distinct cucullus at the spicule tip. The close relation ofB. fagisp. n. with thexylophilusgroup has been confirmed by DNA sequencing and phylogenetic analysis of the 28S rDNA region.Bursaphelenchus fagisp. n. most closely resemblesB. tokyoensisandB. idius, but can be separated by differences in the arrangement of the male caudal papillae, a unique feature for each species. The taxonomic separation of the new species is also confirmed by the unique molecular profile of the ITS region (ITS-RFLP). The mass presence of dauer juveniles ofB. fagisp. n. in Malpighian tubules of adultT. bicolorleads to degradation of the tubule cellular epithelium and local expansion of its basement membrane. These changes clearly indicate direct pathogenicity of the nematode to its vector insect. In laboratory rearing,B. fagisp. n. can grow and reproduce onBotryotinia fuckelianacultures.