Aporcelinus paramamillatus, Nguyen, Thi Anh Duong, Abolafia, Joaquín, Bonkowski, Michael & Santiago, Reyes Peña-, 2016

Nguyen, Thi Anh Duong, Abolafia, Joaquín, Bonkowski, Michael & Santiago, Reyes Peña-, 2016, Two new species of the genus Aporcelinus Andrássy, 2009 (Nematoda, Dorylaimida, Aporcelaimidae) from Vietnam, Zootaxa 4103 (6), pp. 550-560 : 551-554

Aporcelinus paramamillatus sp. n.

( Figs 1–2 )

Material examined. Six females from one location, in good condition. Morphometrics. See Table 1 .

Description. Female: Moderately slender (a = 21–26) nematodes of medium size, 1.71–2.14 mm long. Habitus visibly curved ventrad upon fixation, C-shaped. Cuticle two-layered, 4 µm thick at anterior region and mid-body and 4–7 µm on tail; inner layer thicker and more refractive than the outer layer. Lateral chords 10–14 µm broad or 12–19% of mid-body diameter. Body pores often obscure, but two cervical dorsal and two ventral are sometimes distinct at the level of the odontophore. Lip region somewhat angular, offset by weak constriction, 2.6–2.8 times as wide as high and 26–31% of body diameter at neck base; lips moderately separated, with protruding labial and cephalic papillae. Amphid fovea cup-shaped, its opening 10–12 µm broad or about one-half of lip region diameter. Cheilostom nearly as long as wide, with no specialization. Odontostyle strong, slightly (1.1–1.2 times) longer than lip region diameter, 5.2–6.5 times as long as wide and 1.1–1.5% of total body length; aperture 12 µm or 46–50% of its total length. Guiding ring simple but distinct and somewhat plicate, located at 12–13 µm or 0.5 times the lip region diameter from the anterior end. Odontophore rod-like, 1.7–2.0 times the odontostyle in length. Pharynx consisting of a slender but muscular anterior section enlarging very gradually into the posterior expansion that is 6.4–8.3 times as long as wide, 2.7–3.4 times the corresponding body diameter long, and occupies 47–56% of total neck length; gland nuclei located as follows (n = 1): DO = 58, DN = 62, S1N1 = 75, S1N2 = 79, S2N = 92. Nerve ring at 163–212 µm or 31–35% of total neck length from the anterior end. Pharyngointestinal junction bearing a distinctly developed dorsal lobe; cardia conical, 12– 18 x 8–15 µm. Genital system didelphic-amphidelphic, with both branches almost equally and moderately developed, 157–224 µm long or 9–12% of total body length: ovaries 57–177 µm long, surpassing the oviduct-uterus junction; oviduct 65–106 µm long or 0.9–1.4 times the body diameter, and consisting of a slender portion and a moderately developed pars dilatata; a narrowing separates oviduct and uterus; uterus 71–94 µm long or 1.0–1.6 times the corresponding body diameter long, tripartite, consisting of a short and wider proximal region, a narrower intermediate section with no lumen, and a nearly spherical distal part; uterine egg 90 x 55 µm, with irregular shell; vagina extending inwards 26–32 µm or 32–43% of body diameter, with pars proximalis 16– 22 x 18–22 µm and somewhat sigmoid walls surrounded by weak musculature, pars refringens consisting of two drop-shaped pieces 6– 7 x 4–6 µm and a combined width of 9–12 µm, and pars distalis 3–5 µm long and visibly refractive; vulva a transverse slit. Prerectum 1.8–2.2, rectum 1.0–1.2 times the anal body diameter long. Tail conical with finely rounded tip, dorsally and ventrally convex, ending in a short peg-like terminus, occasionally slightly re-curved dorsad; hyaline portion very short; caudal pores two pairs at the anterior part of tail, one subdorsal, the other sublateral.

Male: Unknown.

Diagnosis. The new species is characterized by its 1.71–2.14 mm long body, lip region offset by weak constriction and 21–22 µm broad, odontostyle 22–24 µm at its ventral side or 1.1–1.2 times the lip region diameter, neck 451–503 µm long, pharyngeal expansion 183–251 µm long or 46–56% of total neck length, uterus tripartite and 71–94 µm long or 1.0–1.6 times the corresponding body diameter long, V = 53–54, tail conical (27–34 µm, c = 50–77, c’ = 0.6–0.9) ending in a peg-like terminal portion and not visibly re-curved dorsad, and male absent.

Relationships. This species is very similar to A. mamillatus ( Williams, 1959) Álvarez-Ortega & Peña- Santiago, 2011 in its general morphology and many morphometrics, but it can be distinguished by several significant differences: broader lip region (21–22 vs 19–20 µm), smaller odontostyle (22–24 vs 25–29 µm, 1.1–1.2 vs 1.3–1.5 times the lip region diameter, n=9) with shorter aperture (46–50 vs 57–61% of its total length), more posterior S2N (92 vs 83–86) and more posterior vulva (V = 53–54 vs V = 49–52).

Type locality and habitat. Northern Vietnam, Cat Ba National Park, Hai Phong Province (GPS coordinates: 20º 47'45'' N and 107º 00'40''E, elevation 170 m), in soil of a secondary forest with Cinnamomum sp. as the dominant plant species. One female was collected near the same location in the rhizosphere of Zea mays L. growing in an area of intensive agricultural crops alongside the National Park.

Type material. Female holotype and four females paratypes deposited in the nematode collection of the University of Jaén, Spain. One female paratype in the nematode collection of the Institute of Ecology and Biological Resources ( IEBR), Hanoi, Vietnam.

Etymology. The specific epithet means ‘near mamillatus ’ as the new species resembles A. mamillatus in many aspects.

Figures

FIGURE 1. Aporcelinus paramamillatus sp. n. (Female). A: Lip region in surface, lateral view. B: Anterior region in median, lateral view. C: Neck region. D: Anterior genital branch. E: Entire. F, G: Posterior body region.

FIGURE 2. Aporcelinus paramamillatus sp. n. (Female, LM). A: Entire. B, C: Anterior region in lateral, median view. D: Pharyngeal expansion. E: Pharyngo-intestinal junction. F: Anterior genital branch. G: Anterior region in lateral, surface view. H: Vagina. I: Uterine eggs. J: Posterior body region. K, L: Caudal region. (Scale bars: A = 200 µm; B, C, G, H, K, L = 10 µm; D, F, I = 50 µm; E, J = 20 µm.)

Tables

TABLE 1. Morphometrics of Aporcelinus paramamilatus sp. n. Measurements in Μm (except L, in mm), and in the form: mean ± standard deviation (range).

Locality		Cat Ba National Park (Hai Phong Province)
Habitat		Cinnamomum sp.	Maize
Character	n	Holotype (♀) Paratypes (4♀♀)	♀
L		1.71 1.98 ± 0.20 (1.71–2.14)	1.86
a		25 23.4 ± 1.7 (21.1–25.1)	26
b		3.8 4.1 ± 0.3 (3.8–4.5)	4.1
c		55 64.7 ± 13.2 (50.2–76.8)	77
c'		0.8 0.7 ± 0.1 (0.6–0.9)	0.6
V		54 53.4 ± 0.5 (52.9–53.9)	54
Lip region diam.		21 22 ± 0.5 (21–22)	21
Odontostyle length at ventral side		24 23.5 ± 1.0 (22–24)	24
Odontophore length		45 48.5 ± 1.9 (45–49)	45
Neck length		451 474.0 ± 21.3 (451–503)	457
Pharyngeal expansion length		183 239.0 ± 13.3 (219–251)	234
Diam. at neck base		67 74 ± 4.6 (70–81)	69
at midbody		69 84.5 ± 7.5 (75–92)	71
at anus		39 42.5 ± 3.9 (39–47)	37
Prerectum length		73 82.5 ± 3.3 (77–84)	80
Rectum length		41 48 ± 3.0 (44–51)	44
Tail length		31 31.5 ± 3.6 (27–34)	24