Pratylenchoides ojcowensis, Winiszewska & Dobosz & Malewski & Skwiercz, 2020

Winiszewska, Grażyna, Dobosz, Renata, Malewski, Tadeusz & Skwiercz, Andrzej, 2020, Description of Pratylenchoides ojcowensis sp. nov. (Nematoda: Merlinidae) from Polish Jurassic Highland, Zootaxa 4742 (1), pp. 117-128 : 119-121

Pratylenchoides ojcowensis sp. nov.

( Figures 1–4 )

Measurements. Measurements of holotype female, 4 paratype females and 15 paratype males of P. ojcowensis sp. nov. are given in Table 1 .

Description. Body tapering towards both ends, bent ventrally after killing. Cuticle with well-marked annulation. The width of the annuli at midbody region 1.3–2.1 μm in females and 1.1–1.9 μm in males. Lateral field with 6 lines in the middle part of body, outer bands wider, sometimes partially areolated. Lines usually regular but some- times discontinuous or tangled. Head of both females and males conical, slightly rounded anteriorly, not separated from the body contour. In males the head is slightly higher than in females. The ratio of head width to height is 1.8–2.3 in males and 2.3–2.4 in females. Head in both sexes with 4–5 annuli. Basal plate of cephalic framework well developed, its posterior extension extending almost 3 annuli. Anterior and posterior cephalids distinct, lying 5–7 and 10–13 annuli behind the cephalic framework respectively. Stylet relatively short (20.3–21.3 µm in females, 17.7–20.9 µm in males) with oval knobs directed more or less posteriorly. Stylet base 5.2–5.7 µm wide in females and 4.0–5.0 in males. Dorsal pharyngeal gland orifice located 2.2–3.1 µm from the stylet base. Hemizonid 1–3 annuli wide, located 2–3 annuli anterior to excretory pore. Deirids at level of or slightly posterior to hemizonid. Median bulb oval, larger in females than in males; with the ratio of length to width also larger in females (1.4–1.7 vs 1.8–2.4). Dorsal pharyngeal nucleus located anterior to the cardia and two subventral pharyngeal nuclei located posterior (dCss). Pharyngeal glands overlapping intestine dorsally, by 1.8–2.6 times corresponding body diameter (all observations of pharyngeal glands are given only for females because these structures were not clearly visible in males). Intestinal fasciculi visible in most specimens.

Female. Vulva thick, approximately 12 μm wide, slightly raised. Vagina with straight walls, perpendicular to the body axis, occupying about 50% of the corresponding body diameter. Spermatheca rounded to oval, axial, filled with rounded sperm. Female tail cylindrical with maximum 29 annuli. Tail terminus broadly rounded, annulated, final annuli wider than others. Phasmids located 27–37 µm anterior to the end of the tail.

Male. Tail conical, curved to the dorsal side in about 1/4 of the length, with a terminal finger-shaped part bent ventrally. Spicules slightly curved ventrally, gubernaculum narrow with hook-shaped distal part. Caudal alae 57.5– 69.5 µm long, 7.5–9.7 µm wide with crenate margins. Phasmids located 21–37 µm anterior to the end of the tail.

Type locality and habitat. Polish Jurassic Highland from soil around tangled roots of Elymus sp. and Trifolium sp. in xerothermic grasslands (N 50.22856 E 19.82599) in Ojców National Park, 13.07.2012, leg. Łukasz Flis and Olga Wiśniewska.

Type material. Holotype female, 4 paratype females and 15 paratype males are deposited at the Nematode Col- lection of Museum and Institute of Zoology of the Polish Academy of Science in Warsaw.

Etymology. The species name “ ojcowensis ” refers to the name of National Park where this the new species was found.

Diagnosis. Pratylenchoides ojcowensis sp. nov. is characterized by conical heads with 4–5 annuli continuous with the body contour in both females and males; a relatively short stylet (20.3–21.3 µm females, 17.7–20.9 µm males) with oval stylet knobs directed posteriorly; a dorsal pharyngeal gland nucleus located anterior to the pharyngo-intestinal junction and two subventral pharyngeal nuclei located posterior to the cardia (dCss); a pharyngeal lobe of length about 2 body widths (1.8–2.6); lateral fields with 6 lines in the middle part of the body and sometimes with partially areolated outer bands; the presence of the intestinal fasciculi; round sperm in the spermatheca in females; a female tail with a maximum of 29 annuli and with an annulated tail terminus.

Morphologically, Pratylenchoides ojcowensis sp. nov. is most similar to P. alkani Yüksel 1977 , P. ritteri Sher 1970 , and P. nevadensis Talavera & Tobar 1996 . It is distinguished from these species by the shape of the female head (conoid vs rounded), shorter stylet in females (20.3–21.3 µm vs 22.0–25.0 µm, 21.0–25.0 µm, 22.0–26.0 µm) and differences in 28S rDNA sequences. In addition (as per the original descriptions Yüksel 1977, Sher 1970, Talavera & Tobar 1996) it is distinguished from P. alkani by smaller number of male’s head annuli (4–5 vs 7–9), from P. ritteri it is distinguished by posteriorly directed stylet knobs (vs directed laterally), from P. nevadensis it is distinguished by oval and posteriorly directed stylet knobs (vs rounded and directed laterally). Pratylenchoides ojcowensis sp. nov. can be separated from other species in the ritteri group ( Ryss 2007) by the following. From P. arenarius Brzeski 1998 and P. bacilisimenus Sher 1970 it is distinguished by sperm shape (round vs rod shaped). From P. leiocauda Sher 1970 it is distinguished by having an annulated tail terminus. From P. maqsoodi Maqbool & Shahina 1989 it is distinguished by more head annuli (4–5 vs 2–3). From P. utahensis it is distinguished by having an annulated tail terminus, different shape of the male head (conoid vs rounded-truncate) and differences in 28S rDNA sequences. From P. vassilevi Stoianov & Baicheva 1988 it is distinguished by the shape of the head (conical and continuous with body contour vs broadly rounded and separated from the body contour) and posteriorly directed stylet knobs (vs directed laterally).

The sequencing of the 28S rDNA D2 / D3 segment from sixteen P. ojcowensis sp. nov. specimens yielded 654–742 bp length sequences. Multiple-sequence alignment showed 606 homologous characters in all specimens. Phylogenetic trees generated from partial 28S rDNA sequences with maximum likelihood method using the general time reversible plus gamma substitution model and Pratylenchus thornei ( JX261963 ) as outgroup showed that they form a well-defined separate clade with 99% bootstrap support ( Fig. 5 ).

Figures

FIGURE 1. Pratylenchoides ojcowensis sp. nov. Female: a, Entire body; b, Body anterior region; c, Vulval region; d-f, Pharyn- geal region with nuclei of pharyngeal glands (d—nucleus of dorsal gland; s1, s2—nuclei of subventral glands; C—cardia); g, Spermatheca; h, Lateral field; i, Posterior region. (Scale bars = 10 µm).

FIGURE 2. Pratylenchoides ojcowensis sp. nov. Male: a, Entire body; b, Anterior region; c, Testis with spermatozoids; d, Posterior region with bursa; e, Posterior region with spicules and gubernaculum. (Scale bars = 10 µm).

FIGURE 3. Pratylenchoides ojcowensis sp. nov. Female: a, Entire body; b, Body anterior region; c, Pharynx region with nuclei of pharyngeal glands; d, Spermatheca; e, Lateral field on the vulva level; f–h, tails. (Scale bars: a = 50 µm, b–h = 10 µm).

FIGURE 4. Pratylenchoides ojcowensis sp. nov. Male: a, Entire body; b, Anterior region; c, Posterior region with spicules and gubernaculum; d–f, Lateral field structure: d, on the deirid level, e in the middle part of the body, f, near cloaca. (Scale bars: a = 50 µm, b–f = 10 µm).

FIGURE 5. Maximum Likelihood phylogenetic tree of Pratylenchoides ojcowensis sp. nov. and other Pratylenchoides species based on partial 28S rDNA sequences generated in MEGA7. Pratylenchus thornei served as outgroup species. Bootstrap values are shown on the branches.