Aporcelinus elongicaudatus, Varela-Benavides & Peña-Santiago, 2018

Varela-Benavides, Ingrid & Peña-Santiago, Reyes, 2018, A new species of the genus Aporcelinus Andrássy, 2009 (Nematoda, Dorylaimida, Aporcelaimidae) from Costa Rica, Zootaxa 4450 (4), pp. 489-494 : 490-491

Aporcelinus elongicaudatus sp. n.

( Figs 1 & 2 )

Material examined: Four females from two locations, in good state of preservation.

Morphometrics: See Table 1.

Description. Female: Stout to moderately slender (a = 16–21) nematodes of small to medium size, 0.92–1.05 mm long. Upon fixation, habitus curved ventrad, C-shaped. Cuticle two-layered, 1.5–2.5 µm thick at anterior region, 2.0–2.5 µm at mid-body and 2.5–3.0 µm on tail; outer layer thin, smooth and with nearly constant thickness throughout the body; inner layer thicker and more refractive than the outer one, especially perceptible at caudal region. Lateral chord 5.0–7.5 µm broad, occupying less than one-sixth (11–15%) of mid-body diameter. Body pores, if present, obscure. Lip region angular, offset by weak but distinct constriction, 2.8–3.0 times as broad as high and one-fourth to one-third (25–32%) of body diameter at neck base; lips moderately separate, with protruding papillae. Amphid fovea funnel-like, its opening 7.0–7.5 µm broad or up to one-half (45–49%) of lip region diameter. Cheilostom a truncate cone, slightly longer than broad, with no differentiation. Odontostyle strong, barely longer (1.0–1.2 times) than lip region diameter, 6.5 times longer than broad and 1.53–1.91% of total body length; aperture 7.0–8.0 µm or ca. one-half (45–50%) of the odontostyle length. Guiding ring simple but distinct, located at 8.0–9.5 µm or 0.5–0.6 lip region diameters from the anterior end. Odontophore rod-like, 1.8–2.0 times the odontostyle length. Pharynx consisting of a slender but muscular anterior section gradually enlarging, and a posterior expansion 4.9–6.6 times as long as wide, 2.5–3.0 times the corresponding body diameter, and occupying ca. one-half (45–55%) of the total neck length; pharyngeal gland nuclei and orifices obscure in the specimens examined. Nerve ring located at 106–108 µm or 35–38% of total neck length from the anterior end. Pharyngointestinal junction bearing a small but appreciable dorsal lobe; cardia conical, 13.0 x 11.5 µm. A dorsal cell mass is present a short distance behind the pharyngo-intestinal junction. Genital system didelphic-amphidelphic, with both branches equally developed and very variably sized, 95–135 µm long or 10–13% of body length: ovaries also very variable in length (65–91 µm), nearly always reaching and surpassing the oviduct-uterus junction; oviduct 42–52 µm long or 0.9–1.0 times the body diameter, and consisting of a slender part composed of prismatic cells and a poorly developed pars dilatata; a narrowing surrounded by a shallow sphincter separates the oviduct and uterus; uterus 33–41 µm long or 0.70–0.85 times the corresponding body diameter in the specimens examined, but probably longer as it appears visibly convoluted, its distal part somewhat dilated and containing sperm cells in at least one specimen; uterine egg 79– 82 x 36–43 µm, with thick and irregular shell; vagina extending inwards 20–23 µm or 30–45% of body diameter: pars proximalis 12.5–15.5 x 11.0–13.5 µm and with slightly sigmoid walls surrounded by weak musculature, pars refringens consisting of two trapezoidal to drop-shaped pieces 3.5–5.5 x 2.5–3.0 µm and a combined width of 6.0–7.0 µm, and pars distalis 3.5–5.0 µm long and rather refractive; vulva a transverse slit. Prerectum 1.5–2.0, rectum 1.4–1.5 times the anal body diameter in length. Tail conical elongated, consisting of two portions, the anterior more convex and tapering more visibly, and the posterior, longer than the anterior, tapering more gradually to a finely rounded tip, and visibly bent dorsad, showing a distinct dorsal concavity; inner cuticle layer not reaching the tail tip and not merging; hyaline portion 21 µm long, occupying 30% of tail length; caudal pores two close pairs, situated a short distance (8.5, 12.5 µm from anus), one lateral, another slightly subdorsal.

Male: Certainly existing as one female contains sperm cells, but not collected.

Diagnosis. Aporcelinus elongicaudatus sp. n. is characterized by its 0.92–1.05 mm long body, lip region offset by weak constriction and 15 µm broad, odontostyle 15–18 µm or 1.0–1.2 times the lip region diameter, neck 270– 300 µm long, pharyngeal expansion 130–150 µm long or 45–55% of total neck length, uterus 33–41 µm long or 0.70–0.85 times the corresponding body diameter (but probably longer), vulva transverse (V = 49–51), and tail conical elongated and dorsad bent (45–71 µm, c = 14–22, c’ = 2.0–3.2).

Relationships. The new species is easily recognizable and distinguishable from its congeners by the conical elongate caudal region (c = 14–22, c’ = 2.0–3.2 vs c -ratio only exceptionally under 25, and c’ only exceptionally over 2.0), bent dorsad. With its small general size (body less than 1.20 mm long) and nearly equatorial vulva, it resembles A. granuliferus ( Cobb 1893) Andrássy 2009 , A. seychellensis ( Andrássy 2009) Andrássy 2011 , and A. yucatanensis ( Chitwood 1938) Peña-Santiago & Abolafia 2016 . Leaving aside the morphology of tail, the new species differs from A. granuliferus (see recent data by Peña-Santiago & Abolafia 2016; Nguyen et al. 2017) in having (vs lacking) a distinct hyaline portion at tail tip. From A. seychellensis in its comparatively shorter odontostyle (1.0–1.2 vs 1.3–1.6 times the lip region diameter) and uterus length (33–41 vs 105–159 µm). And from A. yucatanensis in its less offset lip region (weak vs deep constriction) and more posterior vulva (V = 49–51 vs V = 45–48).

Type locality and habitat. Costa Rica, Alajuela province, Valverde Vega, Bajos del Toro (10°12'56.8''N latitude, 84°18'47.2''W longitude, altitude 1653 m.a.s.l), collected from soil of a pre-montane tropical forest. This locality is part of the Parque Nacional del Agua influence area.

Other locality and habitat. Costa Rica, Alajuela province, San Carlos, Venecia (10°20'05.6''N latitude; 84°18'49.1''W longitude, altitude 794 m. a.s.l). This locality is also part of Parque Nacional del Agua influence area.

Type material. Female holotype and two female paratypes deposited with Laboratorio de Nematología, Instituto Tecnológico de Costa Rica. One female paratype with nematode collection of Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Spain.

Etymology. The specific epithet refers to the typically elongate caudal region of this species.

Remarks. In spite of the low number of specimens examined, the characterization of the new species does not represent any difficulty, and, most importantly, the separation from its congeners is especially easy on the basis of the peculiar morphology of its caudal region.

Figures

FIGURE 1. Aporcelinus elongicaudatus sp. n. from Costa Rica (Female). A: Entire. B, C: Anterior region in lateral, median view. D: Neck. E: Anterior region in lateral, surface view. F: Genital system. G, I: Caudal region. H: Vagina. J: Pharyngointestinal junction. (Scale bars: A = 200 µm; B, C = 10 µm; D, F = 50 µm; E, H = 5 µm; G, I, J = 20 µm.)

FIGURE 2. Aporcelinus elongicaudatus sp. n. from Costa Rica (Female, LM). A: Entire. B, C: Anterior region in lateral, median view. D: Neck. E: Anterior region in lateral, surface view. F: Genital system. G: Caudal region. H: Uterine egg. I: Posterior body region. J: Vagina. (Scale bars: A = 200 µm; B, C = 10 µm; D, F = 50 µm; E, J = 5 µm; G–I = 20 µm.)