Xiphinema penevi, Lazarova, Stela, Peneva, Vlada & Kumari, Shesh, 2016

Lazarova, Stela, Peneva, Vlada & Kumari, Shesh, 2016, Morphological and molecular characterisation, and phylogenetic position of X. browni sp. n., X. penevi sp. n. and two known species of Xiphinemaamericanum-group (Nematoda, Longidoridae), ZooKeys 574, pp. 1-42 : 12-19

Taxon classification Animalia Dorylaimida Longidoridae

Xiphinema penevi sp. n. Figures 15, 16, 17, 18, 19, 20, 21, 22, 23

Measurements.

See Tables 4, 5, 7.

Description.

Females. Body open spiral to C shaped. Thickness of the cuticle at postlabial region 1 μm, 1-1.5 μm at mid-body and 2-2.5 μm at post-anal region, outer cuticle layer not reaching the tail end. Labial region flat anteriorly, laterally rounded, set off from the rest of the body by constriction, 2.5-4 μm high. Amphideal fovea hardly visible, its opening 4 μm in a paratype specimen (40-47 % of the corresponding body width); Distance between first and second guide ring in specimens with retracted odonostyle, 2.5-5 μm long. Odontophore with well developed flanges, 6-9 μm wide, often a small vestigium located in odonthophore area. Pharyngeal characters presented at Table 4. Dorsal nucleus 2.5-3 μm diam., ventrosublateral nuclei well vis ible, 2-2.5 μm. Prerectum indistinct, rectum 21.6 ± 1.8 (19-24) μm, n=8, c 1.3 of corresponding body width. Reproductive system amphidelphic, symbiotic bacteria present in the ovaries. Uteri short, ovejector not developed, only in one specimen a structure resembling ovejector was observed (Table 5); vagina c. 2/3 of the corresponding body width, pars proximalis vaginae with well developed wall. Tail conoid, dorsally convex, ventrally slightly concave, gradually narrowing to a pointed tip, two distinct pairs of caudal pores.

Male. Not found.

Juveniles. The scatter diagram based on functional and replacement odontostyle, and body length revealed the presence of four juvenile stages (Fig. 23). As in most species of the Xiphinema americanum -group there is a gradually decreasing of c‘ values with successive stages which reflects increasing body width while the tail length is more or less similar in juveniles and adults.

Type locality and plant association.

Ifrane, Morocco, Quercus ilex L. forest.

Type material.

The holotype, 7 paratype females and juveniles from all stages are deposited in the nematode collection of the Institute of Biodiversity and Ecosys tem Research, Sofia, Bulgaria. Other paratypes deposited as follows: 2 females in the USDA Nematode Collection, Beltsville, Maryland, USA; 2 females in the Nematode Collection of the Institute of Plant Protection, Bari, Italy; 1 female in the Wageningen Nematode Collection (WANECO), Wageningen, the Netherlands. Three ribosomal sequences (18S, ITS2 and D2-D3) of Xiphinema penevi sp. n. are deposited in GenBank (for accession numbers see Table 2).

Sequence and phylogenetic analyses.

Sequences for three gene regions were obtained (18S, D2-D3 and ITS2). BLAST at NCBI using any of these sequences as queries revealed highest similarity to Xiphinema pachtaicum (99% for 18S, 6 nt difference), two populations of Xiphinema incertum Lamberti, Choleva & Agostinelli, 1983 from Spain (99% for D2-D3, 1 and 3 nt difference) and Xiphinema pachtaicum (90% for ITS2). In both 18S and D2-D3 phylogeny reconstructions Xiphinema penevi sp. n. was part of well supported clades with other species of Xiphinema pachtaicum -subgroup ( Xiphinema pachtaicum , Xiphinema parapachydermum for 18S and Xiphinema incertum , Xiphinema pachtaicum , Xiphinema parapachydermum , Xiphinema plesiopachtaicum , Xiphinema pachydermum Sturhan, 1983 for D2-D3). In the phylogeny reconstruction based on ITS2 sequences, the species grouped with two other Xiphinema pachtaicum populations.

Diagnosis and relationships.

Xiphinema penevi sp. n. is characterised by specific combination of traits: slender body of medium size (1.54-1.85 mm), lip region rounded laterally, flattened anteriorly, separated from the body by a constriction, odontostyle 72-79 μm long, post-equatorial vulva position (V=56-58%), symbiont bacteria present in ovaria, female tail 26-32 μm long (c=50.8-61.2 and c’=1.7– 1.9), conoid dorsally convex ventrally slightly concave with pointed tip, and specific ribosomal sequences (18S and ITS2). The alpha-numeric codes based on average values (ranges given in parentheses) using the polytomous key by Lamberti et al. (2004) are: A2, B3, C3 (4), D1 (2), E2, F2 (1), G2, H1, I2 (1). Subsequently described species Xiphinema parasimile , Xiphinema parabrevicolle , Xiphinema parapachydermum , Xiphinema paratenuicutis ( Barsi and Lamberti 2004, Gutiérrez-Gutiérrez et al. 2012) Xiphinema plesiopachtaicum , Xiphinema vallense and Xiphinema astaregiense ( Archidona- Yuste et al. 2016) and Xiphinema browni sp. n. have been also compared. Species having most similar morphometrics with Xiphinema penevi sp. n. were: Xiphinema pachtaicum , Xiphinema plesiopachtaicum , Xiphinema browni sp. n., Xiphinema vallense and Xiphinema parasimile . Due to the close relationships based on phylogenetic analyses Xiphinema incertum , Xiphinema pachydermum Sturhan, 1983 and Xiphinema parapachydermum were also compared. Xiphinema penevi sp. n. can be differentiated morphologically from:

Xiphinema pachtaicum by its shorter odontostyle av. 77 (72-79) vs 83 μm in holotype, av. 84 (78-88.5) in the present study, 89 (85-97) in females from Ethiopia, and distance of oral aperture to guide ring (68 (66-71) vs 78 in holotype, 77 (73-80) in the present study; shorter pharyngeal bulb (65-72 vs 75-80 μm) in the present study; different tail shape (conoid with gradually pointed tip vs conoid, subdigitate), outer cuticular layer not reaching vs reaching tail tip. ( Lamberti and Siddiqi 1977, Getaneh et al. 2015);

Xiphinema plesiopachtaicum by the position of the amphideal fovea aperture (posterior vs at constriction level); its somewhat shorter odontostyle (72-79 vs 77-89 μm) and uteri (104 vs 138 μm); different position of the dorsal nucleus (DN in front of or at the level of DO (beginning of cuticular lining of the bulb) vs DN below the level of DO); different tail shape (ventrally slightly concave vs straight), smaller values for c and larger for c’ ratios (c=50.8-61.5 vs c=62.5-88.7; c’=1.7– 1.9 vs c’=1.3– 1.7);

Xiphinema vallense by the position of amphideal fovea (posterior constriction vs on the lips); its shorter body (L=1.69 (1.5-1.85) vs 2.01 (1.83-2.22), different position of dorsal nucleus (DN in front or at the level of DO vs DN below the level of DO); different tail shape (ventrally slightly concave vs straight) smaller values for c and larger values for c’ ratios (c=50.8-61.5 vs c=58.2-86.3; c’=1.7– 1.9 vs c’=1.4– 1.7), longer hyaline part (8-10 μm vs 6.5-8.5 μm);

Xiphinema browni sp. n. by its somewhat shorter body (L=1.69 (1.5-1.85) vs 2.03 (1.8-2.40) mm and longer bulbus (65-72 vs 53-69) μm; lower (2.5-4 vs 4-7 μm) and differently shaped lip region (not expanded vs expanded); different location of the dorsal nucleus (DN=9.9-12.9 % vs DN=12.7-21.1%); different vagina shape (funnel- vs bell-like Figs 16, 18);

Xiphinema parasimile by its somewhat shorter body (L=1.69 (1.5-1.85) vs 1.99 (1.75-2.26) mm in type population and avs. 1.78 -1.82 (1.56-2.04) in females from Bulgaria), different lip region shape (laterally rounded vs not rounded), the different location of dorsal nucleus (DN 9.9-12.9 % vs 13.6-18.6 %), longer bulbus (65-72 vs 55.5-63 μm) (Table 4); different vagina shape (funnel vs bell-like), structure of uteri (ovejector not present vs ovejector and separate uteri present) and length of uterus (36-68 vs 27-46 μm in type population and 27-39 μm in population from Bulgaria (Table 5); shorter tail (av. 29 (26-32) vs 33 (30.3-37.1) in the type population and 30-32 (27-35) in females from Bulgaria, c’ =1.8 (1.6-1.9) vs 2.02 (1.79-2.28) in the type population and 2.0 (1.7-2.3) in females from Bulgaria) ( Barsi and Lamberti 2004, Lazarova et al. 2008);

Xiphinema incertum by its different tail shape (elongate conoid vs bluntly conoid, ventrally slightly concave vs straight) and larger c’ values ( c’ =1.8 (1.6-1.9) vs c’ =1.5 (1.4-1.7) in type material and 1.2 (0.9-1.3) in specimens from Spain, larger a values (a=61 (57-2-65) vs a=57 (56-58) in type population and a=49.7 (44.6-52.5) in the population from Spain and different vagina shape compared with females from Spain, this character not described for the type population ( Lamberti et al. 1983, Gutiérres-Gutiérres et al. 2012);

Xiphinema pachydermum by its shorter body (L=1.69 (1.5-1.85) mm vs 2.24 (2.08-2.44) mm), different location of dorsal nucleus (DN=10-13 % vs DN=15-20%), presence of symbiont bacteria in ovaria vs not present; males occurrence (not present vs abundant);

Xiphinema parapachydermum by its different tail tip (not so acute and not with dorso-ventral depression) and in having symbionts in its ovaries vs absent, males occurrence (not present vs abundant).

Etymology.

The new species is named after Dr Lyubomir Penev, an internationally recognised publisher and authority in entomology and ecology as acknowledgement of his invaluable help and support provided to one of the authors (VP) in her research activities.