Deladenus nitobei n. sp. (Tylenchomorpha: Allantonematidae) isolated from Sirex nitobei (Hymenoptera: Siricidae) from Aomori, Japan, a new member of the siricidicola superspecies

Abstract

Deladenus nitobein. sp., a parasite of a woodwasp species,Sirex nitobei, is described based on its typological characters and molecular profiles of part of the small subunit D2-D3 expansion segments of the large subunit and internal transcribed spacer region of the ribosomal RNA gene, as well as part of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene. Adult host woodwasps emerging from dead Japanese red pine logs,Pinus densiflora, collected at Aomori, Japan, were dissected and examined for nematode association. The new species was isolated from the body cavity and reproductive system ofS. nitobeias large parasitic females and small parasitic juveniles. The nematodes were cultured successfully on 1.0% malt extract agar medium, inoculated withSirex-associated fungus,Amylostereumareolatum. The mycophagous adult nematodes were characterised by the relative position of the excretory pore, located at 25 (19-28) and 25 (18-30)μm anterior to the hemizonid in the male and female, respectively, and a broad female tail with a rounded distal end. Typologically, the new species forms a cryptic species complex withD. siricidicolaandD. canii. In addition, the new species andD. siricidicolashare the same host wasp, tree and fungal species in Japan. However, the cryptic species can be separated from each other based on the described morphological and molecular sequence differences in the mtCOI gene.

Characterisation of the dimorphic Deladenus beddingi n. sp. and its associated woodwasp and fungus

“…Mycophagous males of D. beddingi n. sp. also differ from D. nitobei in the values of the ratios a (55 (41-61) vs 64.3 (55.8-74.1)) and b (15.4 (11.2-17.4) vs 21.5 (19.5-24.3)) (Kanzaki et al, 2016) (see Table 5). The length of the spicules of the mycophagous males is also shorter than that observed in D. proximus (21.5 (18-25) vs 25 (24-38) μm) ( Table 5; Bedding, 1974) and D. nitobei (40 (38-44) μm) (Kanzaki et al, 2016).…”

“…also differ from D. nitobei in the values of the ratios a (55 (41-61) vs 64.3 (55.8-74.1)) and b (15.4 (11.2-17.4) vs 21.5 (19.5-24.3)) (Kanzaki et al, 2016) (see Table 5). The length of the spicules of the mycophagous males is also shorter than that observed in D. proximus (21.5 (18-25) vs 25 (24-38) μm) ( Table 5; Bedding, 1974) and D. nitobei (40 (38-44) μm) (Kanzaki et al, 2016). The hemizonid and excretory pore of the males of the new species are located more posteriorly than in D. nitobei (108 (84-134) vs 94 (85-99) μm, and 77 (57-103) vs 69 (65-76) μm, respectively) (Kanzaki et al, 2016).…”

“…Deladenus beddingi n. sp. morphologically resembles D. siricidicola, D. proximus and Deladenus nitobei Kanzaki, Tanaka, Fitza, Kosaka, Slippers, Kimura, Tsuchiya & Tabata, 2016(Kanzaki et al, 2016, but can be distinguished from these species by several morphometric traits, including the value of ratios a, b, c of the mycophagous females and males, ratio b of the infective females, and the morphology of the tail of the mycophagous females, which is narrow and gradually tapering. Having the excretory pore more than 20 μm anterior to the hemizonid was recognised by Chitambar (1991) as a key trait of many dimorphic Deladenus spp.…”

“…There are 26 nominal species in the neotylenchid genus Deladenus Thorne, 1941, including the superspecies D. siricidicola Bedding, 1968 andD. wilsoni Bedding, 1968 that contain four and two species, respectively (Chitambar, 1991;Kanzaki et al, 2016). Ten species of Deladenus are known from North America ( Supplementary Table S1), with nine considered native and one thought to have been introduced from Eurasia (Yu et al, 2009).…”

Some additional bionomic characters of Deladenus nitobei

“…was originally described as an internal parasite of a woodwasp species, Sirex nitobei Matsumura, which emerged from dead logs of Japanese red pine, Pinus densiflora Sieb. & Zucc., collected from Takko, Aomori, Japan (Kanzaki et al, 2016). During the collection of material for the species description, the emergence date and sex of the wasps were recorded, and the dissected wasp bodies were fixed in 100% ethanol and vouchered at the Forest Pathology Laboratory of Forestry and Forest Products Research Institute, Tsukuba, Japan.…”