Aporcelaimellus rarus, Álvarez-Ortega, Sergio, Abolafia, Joaquín & Peña-Santiago, Reyes, 2013

Álvarez-Ortega, Sergio, Abolafia, Joaquín & Peña-Santiago, Reyes, 2013, Studies on the genus Aporcelaimellus Heyns, 1965 (Nematoda, Dorylaimida, Aporcelaimidae). Four atypical species with simple uterus from Southern Iberian Peninsula, Zootaxa 3630 (3), pp. 401-423 : 414-416

Aporcelaimellus rarus sp. n.

( Figs 6 & 7 )

Material examined. Four females, in variable state of preservation.

Measurements. See Table 3 .

Description. Female: Slender to very slender nematodes of medium size, 1.96–2.34 mm long. Body cylindrical, tapering towards both extremities, but more so towards the posterior end. Habitus curved ventrad after fixation, especially in posterior body region, C-shaped. Cuticle three-layered, 1.5–2.0 μm at anterior region, 3–4 μm in mid-body and 4.5–7.5 μm on tail; outer layer thin and bearing fine but distinct transverse striation, intermediate layer also thin, and inner layer thicker and with radial striation. Cervical lacunae apparently absent. Two dorsal body pores are usually present at level of odontophore, other body pores inconspicuous. Lateral chord 6–13 μm wide or 11–17% of mid-body diameter. Lip region offset by constriction, 2.9–3.1 times as wide as high and about one-fourth (22–29%) of body diameter at neck base. Amphid fovea funnel-shaped, its aperture 7–8 μm or one-half to three-fifths (52–57%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.8–5.0 times as long as wide, as long as lip region diameter, and 0.64–0.74% of body length; aperture 9–11 μm long or occupying two-thirds to three-fourths (68–75%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.7–2.2 times the odontostyle. Anterior region of pharynx enlarging gradually; basal expansion 7.0–9.3 times as long as wide, 3.8–4.5 times as long as body diameter, and occupying 48–52% of total neck length; pharyngeal gland nuclei obscure in the specimens examined. Nerve ring located at 115–165 μm from anterior end or 28–32% of total neck length. Cardia conical, 19 (n=1) x 12–16 μm (n=2); a ring-like structure is present surrounding its junction to pharyngeal base. A dorsal cellular mass is readily perceptible in the best specimens a short distance behind the cardia. Genital system didelphic-amphidelphic, with both branches equally and moderately developed, the anterior 175–215 μm or 9–10% of body length [253 μm or 13% (n=1) of body length with an uterine egg inside], and the posterior 159–224 μm or 8–10% of body length [252 μm or 13% (n=1) of body length with a uterine egg inside]: ovaries reaching but often not surpassing the sphincter level, the anterior 101–189 μm and the posterior 98–195 μm long, with oocytes arranged first in two or more rows, then in a single row; oviduct 74–134 μm long or 1.4–1.7 times the corresponding body diameter, consisting of slender part with prismatic cells and a moderately developed pars dilatata with small but visible lumen; oviduct and uterus separated by a very distinct sphincter; uterus a simple tube 63–74 μm long or 0.8–1.5 times the corresponding body diameter [95, 96 μm (n=1) long or 1.4, 1.5 (n=1) times the corresponding body diameter with an egg inside]; uterine egg ovoid, 87 x 48 μm (n=1), 1.8 (n=1) times as long as wide; vagina extending inwards 21–26 μm or one-third to one-half (34–44%) of body diameter, with pars proximalis 14– 16 x 11–17 μm and somewhat sigmoid walls surrounded by weak musculature, pars refringens with two triangular pieces measuring 6– 8 x 2.5–4.0 μm and with a combined width of 7–9 µm, and pars distalis short, 1–2 μm; and vulva a transverse slit. Prerectum 1.7–4.1, rectum 0.9–1.3 times the anal body diameter. Tail short, conical with rounded terminus and with a more or less marked (but readily perceptible) dorsal concavity in its posterior half; inner core very short, occupying up to one-half of tail length; inner cuticle layer not reaching the tail tip, hence a short but distinguishable terminal hyaline portion is always present; caudal pores two pairs, one subdorsal in the anterior portion of tail, another sublateral at the middle of the tail.

Male: Not found.

Diagnosis. This species is characterized by its body 1.96–2.34 mm long, lip region offset by constriction and 14–16 μm broad, odontostyle 15–16 μm long with aperture occupying 68–75% its length, neck 411–518 μm long, pharyngeal expansion 196–270 μm long or 48–52% of total neck length, a dorsal cellular mass at a short distance behind the cardia, uterus 63–96 μm long or 0.8–1.5 times the corresponding body diameter, V = 51–56, female tail short and conical (28–40 μm, c = 50–74, c’ = 0.7–0.9) with rounded terminus and bearing a dorsal concavity at its posterior half, and males unknown.

Relationships. In having medium size, comparatively narrow lip region, and relatively short odontostyle the new species is morphologically close to several species, including A. amylovorus , A. clamus , A. hyalinus sp. n., A. punctatus , A. salicinus , A. samarcandicus and A. waenga , but it can be distinguished from them in the morphology of caudal region equally tapering at both sides and with a weak but perceptible dorsal concavity, and from all of them except A. hyalinus and A. salicinus in having discontinuous inner cuticle layer at terminal portion of tail. Besides, it differs from A. amylovorus in its larger size (vs body length 1.63–1.79 mm), and shorter odontostyle (vs 17–19 μm long) with larger aperture (vs 58–63% of total odontostyle length), and comparatively shorter tail (vs c’ = 1.1–1.3). From A. clamus in its narrower lip region (vs 17.0–17.5 μm), shorter (vs 19.0–19.5 μm) and more slender odontostyle (4.8–5.0 vs 4.5–4.6 times as long as wide), shorter neck (vs 530–573 μm), and male absent (vs present). From A. hyalinus in its shorter caudal region (vs c = 66–82, c’ = 1.0–1.4, n=47), and male absent (vs present although rare). From A. punctatus in its narrower lip region (vs about 21 μm), shorter odontostyle (vs about 18 μm), shorter female genital branches (vs occupying 24–26% of body length) and shorter tail (vs c’ ratio ca 0.9). From A. salicinus in its narrower lip region (vs 16–18 µm), smaller odontostyle (vs 18–20 µm) with larger aperture (vs 50–53% its length), and male absent (vs present although rare). From A. samarcandicus in its larger (vs 1.47–1.70 mm long) and more slender (a = 30–42 vs a = 25–29) body, narrower lip region (vs 17–19 μm), shorter odontostyle (vs 18–19 μm), shorter neck (b = 4.5–5.0 vs 3.3–3.7), prerectum lacking a blind sac (vs often bearing), and tail longer (vs 20–26 μm). And from A. waenga in its smaller odontostyle (vs 16–19 μm long) with larger aperture (vs 57–68% its length), and shorter neck (b = 4.5–5.0 vs 3.4–4.3).

Finally, the new species also resembles A. deserticola sp. n. and A. obtusicaudatus . It can be separated from A. deserticola in its smaller (vs 18–21 μm long) and more robust (4.8–5.0 vs 5.0–5.8 times as long as wide) odontostyle with larger aperture (vs 55–61% its length), comparatively longer odontophore (1.7–2.2 vs 1.4–1.6 times the odontostyle), shorter neck (b = 4.5–5.0 vs 3.8–4.5), and comparatively shorter tail (vs c’ = 0.9–1.4) bearing (vs lacking) a dorsal concavity. And from A. obtusicaudatus in its narrower lip region (vs 16–23 μm), shorter odontostyle (vs 19–29 μm), female tail conical (vs rounded to conical with broad terminus) with inner cuticle layer showing a marked discontinuity (vs continuous), and male absent (vs present).

Type locality and habitat. Spain, western Andalucía, Cádiz province, Sierra del Pinar, associated with Abies pinsapo .

Other locality and habitat. Spain, eastern Andalucía, Granada province, Sierras de la Sagra, Jurena y Guillimona Natural Park, Sierra Jurena, road from Huéscar to Puebla de Don Fadrique, associated with holm oak trees, pine trees, Retama sphaerocarpa , juniper ( Juniperus sp.) and thyme; and from Jaén province, Sierras de Cazorla, Segura y Las Villas Natural Park, Sierra de Segura, associated to pine trees, juniper ( J. oxycedrus ), thyme and oak ( Quercus coccifera ).

Type material. Female holotype and female paratype, deposited in the nematode collection of the University of Jaén, Spain.

Etymology. The specific epithet is a Latin term meaning ‘rare’ or ‘scarce’, and refers to the few specimens collected of the new taxon.

Figures

FIGURE 6. Aporcelaimellus rarus sp. n. (female). A: Anterior region in median view. B: Same in lateral, surface view. C: Pharyngeal expansion. D: Anterior genital branch. E: Entire body. F: Posterior body region. G: Vagina.

FIGURE 7. Aporcelaimellus rarus sp. n. (LM, female). A: Neck region. B: Anterior region in median, lateral view. C: Anterior genital branch. D: Posterior body region. E: Vagina. F – H: Caudal region. (Scale bars: A = 100 µm, B, F – H = 10 µm; C, D = 50 µm).

Tables

TABLE 3. Morphometric data of Aporcelaimellus rarus sp. n. Measurements in μm (except L, in mm), and in the form: mean ± standard deviation (range).

Population	Sierra de Pinar	Sierra de Jurena	Sierra de Segura	Total range
	Holotype Paratype
Character	n Ƥ Ƥ	Ƥ	Ƥ	4ƤƤ
L	1.99 2.04	2.34	1.96	1.96–2.34
a	35 42	30	30	30–42
b	4.5 5.0	4.5	?	4.5–5.0
c	69 74	68	50	50–74
c'	0.9 0.9	0.7	0.9	0.7–0.9
V	55 53	51	56	51–56
Lip region diam.	14 14	16	14	14–16
Odontostyle length	15 15	16	15	15–16
Odontophore length	25 24	33	30	24–33
Guiding ring from ant. end	7 7	9	9	7–9
Neck length	446 411	518	?	411–518
Pharyngeal expansion length	234 196	270	?	196–270
Diam. at neck base	52 48	71	60	48–71
at mid-body	57 48	78	66	48–78
at anus	31 30	46	44	30–46
Prerectum length	111 123	140	73	73–140
Rectum length	41 38	43	47	38–47
Tail length	29 28	34	40	28–40