Pseudacrobeles (Bunobus) pseudolatus ( Hernández, 1990 ) De Ley, Siddiqi & Boström, 1993

Abolafia, Joaquín & Peña-Santiago, Reyes, 2013, Iberian species of the subgenus Bunobus De Ley, Siddiqi & Boström, 1993 (Nematoda, Rhabditida, Cephalobidae), with description of Pseudacrobeles (Bunobus) rotundilabiatus sp. n. and comments on the subgenus, Zootaxa 3640 (2), pp. 200-212 : 201-204

Pseudacrobeles (Bunobus) pseudolatus ( Hernández, 1990) De Ley, Siddiqi & Boström, 1993

( Figs 1–2 )

Material examined. Three female and one male paratypes, in variable states of preservation.

Morphometrics. See Tables 1 & 2.

Description

Population from Beunza, province of Navarra (3, 1):

Adult: Stout nematodes of very small size, 0.38–0.42 mm long. Body cylindrical, tapering towards both extremities but more so towards the posterior end since the caudal region is conical. Habitus after fixation hardly curved ventrad, C-shaped in females, J- or G-shaped in male. Cuticle annulated, with annuli 1.2 Μm wide at midbody. Lateral field marked by three longitudinal incisures, occupying about one-fifth of body diameter at mid-body and extending to phasmid level. Lip region nearly continuous with the adjacent body and displaying bilateral symmetry: subdorsal and subventral lips rounded and low, lateral lips visibly reduced, cephalic and labial probolae absent, and 6+4 papillae. Amphid aperture small, slit-like, located at base of lateral lips. Oral opening almost triangular with small liplet-like structures extending to lips. Stoma cephaloboid, 2.0 times the lip region width in length: cheilorhabdions bar-shaped in optical section, and gymnostom clearly narrower than cheilostom and as wide as stegostom. Pharyngeal corpus cylindrical, 2.2–2.9 times as long as isthmus; isthmus distinctly demarcated from corpus, reflexed after fixation; and basal bulb pyriform, 1.5 times longer than wide, with well developed valves. Cardia conoid, surrounded by intestinal tissue. Nerve ring embracing the posterior part of corpus, close to isthmus, at 62–72% of the total neck length. Excretory pore at 58–69% (n = 2) of total neck length or 52–57 annuli from the anterior end (R ep), at level of posterior part of corpus. Deirid located in lateral field at level of posterior part of corpus, at 81% (n = 1) of the neck length or 58 annuli from the anterior end (R dei). Intestine with a cardiac part (that is, an anterior section bearing significantly wider lumen) one-half the corresponding body diameter long.

Female: Reproductive system cephaloboid, monodelphic-prodelphic: ovary directed posteriorly, with or without post-vulval double flexure, germinal part not expanded, with oocytes arranged in a single row, and distal part without oocytes; oviduct one-third the corresponding body diameter long; spermatheca well developed, equal in length to body diameter; uterus tubular, nearly two times the corresponding body diameter long, its distal part having slender walls that become thicker proximally; postvulval sac 0.4–0.7 times the corresponding body diameter long; and vagina extending inwards to one-third of body diameter. Rectum 1.4–1.6 anal body widths long, with three rectal muscle cells, two subventral and one dorsal. Tail conical elongated, with 28–32 annuli on its ventral side, ending in an acute mucro, occasionally reduced. Phasmids at 40–42% of tail length.

Male: Genital system monorchic, dextral: testis reflexed ventrally in anterior portion. Spicules curved ventrad: manubrium rounded, calamus narrow, and lamina with a thickened proximal part and a longitudinal incisure. Gubernaculum curved ventrad. Tail conical, slightly curved ventrad, having a terminal, acute mucro. Genital papillae eight pairs, three pairs pre-cloacal and five pairs post-cloacal or caudal: two anterior to phasmid (one lateral and another subventral), one posterior to phasmid (lateral), and three near tail tip (one subdorsal and two subventral); one single mid-ventral papilla located in front of the pre-cloacal lip.

Diagnosis. This species is characterized by a body length of 400–424 Μm long in females and 380 Μm in male, lateral field with three incisures fading out near the phasmid, lip region continuous with the adjacent body, subdorsal and subventral lips rounded, lateral lips rounded but more reduced, stoma 12–14 Μm long, pharyngeal corpus 2.2–2.9 times longer than isthmus, excretory pore and nerve ring at posterior part of pharyngeal corpus, V = 61–62, spermatheca 22–23 Μm long, postvulval sac 0.4–0.7 times the body diameter in length, female tail conical elongated (43 µm, c = 9.3–9.9, c' = 3.3–4.3) ending in an acute mucro, male tail conical (26 µm, c = 14.6, c' = 2.0), spicules 15 µm long, and gubernaculum 9 µm long.

Locality and habitat. Beunza, Atez Valley (province of Navarra), in soil of a forest whose dominant plant tree is Quercus pyrenaica Willd.

Figures

FIGURE 1. Pseudacrobeles (Bunobus) pseudolatus (Hernández, 1990) De Ley, Siddiqi & Boström, 1993 (paratype). A: Neck. B: Anterior end. C, D: Lip region (at lateral view and at frontal view, respectively). E: Entire female. F: Vulva. G: Female genital system. H: Entire male. I, J: Female posterior end. K: Male posterior end.

FIGURE 2. Pseudacrobeles (Bunobus) pseudolatus (Hernández, 1990) De Ley, Siddiqi & Boström, 1993 (paratype, LM). A: Neck. B, C: Anterior end (at superficial view and at stoma level, respectively). D: Vagina. E: Female posterior end (arrow points the phasmid). F: Male posterior end (arrows point some genital papillae).