Xiphinema

Sakai, Hiromichi, Takeda, Ai & Mizukubo, Takayuki, 2011, First report of Xiphinema brevicolle Lordello et Costa, 1961 (Nematoda, Longidoridae) in Japan, ZooKeys 135, pp. 21-40 : 25

Xiphinema sp. Figs 1B, 1D, 1F, 1H34B5B6B

Measurements.

See Tables 2, 3.

Remarks.

These specimens morphometrically resemble Xiphinema paramonovi Romanenko, 1981, except for the clearly different tail length (Table 2). The morphometrics of the specimens partly overlap those of Xiphinema brevicolle . General morphology and DNA information addressed below suggest that these specimens belong to some species related to Xiphinema brevicolle , though a specific species accommodating them was not found. We finally regarded these specimens as an unidentified Xiphinema americanum -group species. Further information is required to identify the specimens as a new species or determine if they represent intra-specific variation of species previously described. No male was detected.

Molecular study.

DNA sequences of 886 bp except for primer regions were obtained for the mitochondrial COI region. The five Xiphinema brevicolle specimens observed had identical sequences, whereas a single nucleotide in the sequence differed among the four specimens of Xiphinema sp. though this variation resulted in no difference between the translated amino acid sequences within the specimens. Sequence identity between these two species was 84.0-84.1%, whereas the sequences of Xiphinema brevicolle and Xiphinema sp. were 80.7 and 80.4-80.5% identical to that of Xiphinema americanum ( He et al. 2005a) respectively, with no gap found among them (Fig. 7). Putative amino acid sequences were available without any stop codon when translations were made from the second base of the obtained sequences. DNA sequences of 1,566 bp except for primer regions were obtained for the 18S rDNA region from one specimen for each species. The difference between sequences of the two species studied here was only a single nucleotide, resulting in 99.9% identity without any gap. DNA sequences of 788-791 bp except primer regions were obtained for the D2/D3 region from four specimens for each species. A single nucleotide variation of sequence among four specimens of Xiphinema brevicolle was observed, whereas no variation of sequence was observed among four specimens of Xiphinema sp. Sequence identity between these two species was 98.1-98.2%, with gaps found.

ML trees inferred for the 18S rDNA and D2/D3 regions placed our specimens in similar clades, which include Xiphinema brevicolle and its junior synonyms by Luc et al. (1998) such as Xiphinema diffusum Lamberti et Bleve-Zacheo, 1979, Xiphinema incognitum Lamberti and Bleve-Zacheo, 1979, Xiphinema taylori Lamberti et al., 1992, as well as other different species like Xiphinema inaequale (Khan et Ahmad, 1975) and Xiphinema lamberti Bajaj et Jairajpuri, 1977 (Figs 8, 9). On the other hand, the ML tree inferred for the COI region didn’t show strong support for such a clade because of a low bootstrap value though several subclades were strongly supported by high bootstrap values (Fig. 10).