Aporcelinus paraseychellensis, 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 : 555-559

Aporcelinus paraseychellensis sp. n.

( Figs 3 ‒5)

Syn. Aporcelinus seychellensis apud Vinciguerra et al. (2014) , nec Andrássy (2009)

Material examined. Three females and one male from two locations, in acceptable condition. Morphometrics. See Table 2 .

Locality Cat Ba National Park Huu Lien Natural Reserve

(Hai Phong Province) (Lang Son Province)

Habitat Cinnamomum sp Machilus sp. and Dimocarpus

Holotype Paratypes sp.

Description. Adult: Stout (a = 16–20) nematodes of medium size, 1.20–1.46 mm long. Habitus variably curved ventrad upon fixation, C-shaped in female, G-shaped in male. Cuticle two-layered, 3–4 µm thick at anterior region, 3.5–5.0 µm in mid-body and 4.0–6.5 µm on tail; inner layer thicker and more refractive than the outer layer. Lateral chord 9 µm broad or 10–13% of mid-body diameter. Body pores often obscure, but two cervical pores are visible on both dorsal and ventral sides at level of odontostyle plus odontophore. Lip region angular, offset by constriction; lips high, separated, with protruding labial and cephalic papillae. Amphid fovea cup-shaped, its opening 9–11 µm broad or 53–63% of lip region diameter. Cheilostom nearly as long as wide, with no specialization. Odontostyle strong, 1.1–1.4 times longer than lip region diameter, 6.2–7.7 times as long as wide and 1.4–1.9% of total body length; aperture 10–11 µm or 46–48% of its total length. Guiding ring simple but distinct, somewhat plicate, located at 9–10 µm or 0.5–0.6 times the lip region diameter from the anterior end. Odontophore rod-like, 1.5–1.8 times the odontostyle length. Pharynx consisting of a slender but muscular anterior section enlarging very gradually in the posterior expansion, which is 5.4–6.8 times as long as wide, 2.8–3.3 times the corresponding body diameter and occupies 49–51% of total neck length; gland nuclei located as follows (n = 1): DO = 58, DN = 62, S1N1 = 75, S1N2 = 82, S2N = 90. Nerve ring at 113 µm or 31% of total neck length from the anterior end. Pharyngo-intestinal junction bearing a distinctly developed dorsal lobe; cardia conical, 10– 14 x 11–12 µm. A dorsal cell mass is present at level of the pharyngo-intestinal junction.

Female: Genital system didelphic-amphidelphic, with both branches equally and moderately developed, 176–308 µm long or 17–21% of total body length: ovaries very variably sized, 79–236 µm long; oviduct 55–94 µm long or 0.8–1.1 times the body diameter and consisting of a slender portion made of prismatic cells and a moderately developed pars dilatata with perceptible lumen; a narrowing separates oviduct and uterus, but a distinct sphincter is lacking; uterus 176–241 µm long or 2.4–2.7 times the corresponding body diameter, tripartite, consisting of a short and wider proximal region, a longer and much narrower intermediate section with no lumen, and a nearly spherical distal part; vagina extending inwards 33–36 µm or 40–47% of body diameter, with pars proximalis 22– 25 x 15–20 µm and somewhat sigmoid walls surrounded by weak musculature, pars refringens consisting of two drop-shaped or trapezoidal pieces 7– 8 x 4–5 µm and a combined width of 9–10 µm, and pars distalis 5–7 µm long and visibly refractive; vulva a transverse slit. Prerectum 1.5–2.0, rectum 1.2–1.3 times the anal body diameter in length. Tail conical with acute tip, ventrally nearly straight or slightly convex, and dorsally first convex and then concave, the tail being slightly re-curved dorsad; cuticle extending until the tail tip, so that a hyaline portion is not observed; caudal pores two pairs, at the middle of tail, one subdorsal, the other lateral.

Male: Prerectum 2.3, cloaca 1.7 times the body diameter at the cloacal aperture. Genital system diorchic, with opposite testes. In addition to the adcloacal pair, located at 9 µm from the cloacal aperture, there is a series of 12 low, regularly spaced (10–16 µm apart) ventromedian supplements, the most posterior three located within the range of spicules. Spicules dorylaimid, 4.6 times longer than wide and 1.8 times longer than body diameter at the cloacal aperture: dorsal side regularly convex and ventral side with barely perceptible hump and hollow; curvature 136º; head 8 x 7 µm, with the dorsal side somewhat longer than the ventral one and weakly curved; median piece occupying less than one-third (29%) of maximum spicule width, reaching the posterior end of the spicule and with a visibly furcate tip; posterior end of spicules 6 µm wide. Lateral guiding pieces 17 µm long or 6.1 times as long as wide, slightly sigmoid and tapering posteriorly. Tail straight ventrally, dorsally first convex and then very weakly concave.

Diagnosis. The new species is characterized by its 1.20–1.46 mm long body, lip region offset by constriction and 16–18 µm broad, odontostyle 20 µm at its ventral side or 1.1–1.4 times the lip region diameter, neck 354–368 µm long, pharyngeal expansion 175–186 µm long or 49–51% of total neck length, a dorsal cell mass present at the pharyngo-intestinal junction, uterus tripartite and 176–241 µm, or 2.4–2.7 times the corresponding body diameter, long, V = 52–54, tail conical with acute tip and slightly recurved dorsad (33–42 µm, c = 33–45, c’ = 0.9–1.2), spicules 62 µm long, and 12 regularly spaced ventromedian supplements, three of them within the range of spicules.

Relationships. The new species is very similar to A. seychellensis Andrássy, 2011 in its general morphology and morphometrics, but differs from the type population of that species in its larger general size (body length 1.20–1.46 (n = 4) vs 0.92–1.07 mm (n=4); neck length 354–368 vs 272–330 µm), much larger genital branches (17–21% vs 7–13% of total body length each), more posterior vulva (V = 52–54 vs V = 45–52), shorter female tail (32–36 vs 36–40 µm, c = 33–45 vs c = 25–29) and male present (vs absent). Especially relevant in the type population are the very short female genital branches, probably because the uterus is short and simple.

Vinciguerra et al. (2014) studied two A. seychellensis populations from Ecuador that differ from the type populations in their larger general size [body 1.08–1.55 (n=26) vs 0.92–1.07 (n = 4) mm long] and comparatively shorter female tail (c = 29–42 vs c = 25–29). Besides, the female genital branches are larger (12–22 vs 7–13% of total body length), but lower values in the Ecuador material may be due to the convoluted, tripartite uterus. Leaving aside the fewer ventromedian supplements (7–9 vs 12; two vs three situated within the range of spicules) in males from Ecuador, there is no significant difference between this material and the Vietnamese specimens herein studied. Taking into consideration that only one male of the new species has been collected, the differences in number and arrangement of ventromedian supplements are provisionally regarded as intraspecific variability and, consequently, we consider the specimens from Ecuador and Vietnam to be conspecific.

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), collected from soil in a tropical forest with Cinnamomum sp. as dominant plant species.

Other locality and habitat. Northern Vietnam, Huu Lien Natural Reserve, Lang Son Province, (GPS coordinates: 21º 42'51'' N and 106º 21'48''E, elevation 502 m), in soil of the forest where the dominant plant species were Machilus sp. and Dimocarpus sp.

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

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

Figures

FIGURE 3. Aporcelinus paraseychellensis sp. n. A: Lip region in surface, lateral view. B: Anterior region in median, lateral view. C: Neck region. D: Female, anterior genital branch. E: Female, posterior body region. F: Female, entire. G: Male, entire. H: Male, posterior body region. I: Spicule. J: Lateral guiding piece.

Tables

TABLE 2. Morphometrics of Aporcelinus paraseychellensis sp. n. Measurements in Μm (except L, in mm).

Character	n ♀	♀	♂	♀
L	1.46	1.31	1.40	1.19
a b	17 4.1	18 3.7	20 3.8	16 3.3
c	45	38	33	34
c' V/T	0.9 54	1.0 52	1.2 53	0.9 53
Lip region diam.	17	18	16	17
Odontostyle length at ventral side	20	20	20	20
Odontophore length Neck length	36 354	37 354	– 368	35 363
Pharyngeal expansion length	175	175	186	184
Diam. at neck base	77	66	65	56
at midbody at anus	88 35	74 34	69 35	73 37
Prerectum length	72	59	80	54
Rectum length Tail length	46 33	42 34	60 42	43 35
Spicule length	–	–	62	–
Ventromedian supplements	–	–	12	–