Xiphinema japonicum n. sp. (Nematoda: Longidorinae) from the Rhizosphere of Japanese Podocarpus macrophyllus (Thunb.) a Cryptic Species Related to Xiphinema bakeri Williams 1961

摘要

Xiphinema japonicum n. sp., isolated in Ningbo, China, from the rhizosphere of Podocarpus macrophyllus (Thunb.) imported from Japan is described. The new species belongs to Xiphinema non-americanum group 7 and is characterized by medium body length (3.0–3.7 mm), total stylet length 190–201 μm, vulva located anteriorly (V = 30.5%–35.3%), two equally developed female genital branches without uterine differentiation (no Z or pseudo-Z organ and/or spines in the uteri), short tail, convex-conoid with subdigitate peg in terminus, and absence of males. The species has four juvenile developmental stages (J1 was not found). The polytomous identification codes of the new species are (codes in parentheses are exceptions) A4-B4-C4-D5(4)-E2(3)-F3(4)-G2(3)-H2-I3-J4-K?-L1. Morphologically, the new species is mainly characterized by combination of the codes C4 and E2(3), making the species unique and different from other species in the genus. It is most similar to the North American species Xiphinema bakeri, herein considered as its cryptic species by the nature of high morphological similarity, but with significant differences in DNA sequences in nearly full length 18S, ITS1, 28S D2/D3, and cytochrome c oxidase subunit 1 sequences. The second morphologically close species is Xiphinema setariae from which the new species could be separated based on morphological and molecular characters. Morphological comparisons with phylogenetically related species are also discussed.