Paracrobeles psammophilus Navarro and Lluch, 1999

Abolafia, Joaquín & Peña-Santiago, Reyes, 2015, Some rare species of cephalobs (Nematoda: Rhabditida: Cephalobidae) from Southern Iberian Peninsula, Journal of Natural History 50, pp. 557-581 : 569-575

Paracrobeles psammophilus Navarro and Lluch, 1999 ( Figures 5 , 6A – F )

Material examined

Two females and two males from one locality.

Morphometrics

See Table 1.

Description

Adult. Stout nematodes, body 0.45 – 0.49 mm long. Habitus somewhat curved ventrad after fixation. Cuticle deeply annulated and tessellated, distinctly divided in blocks. Lateral field with four longitudinal incisures or two wings separated by a broad groove, occupying 15 – 25% of midbody diameter, and nearly reaching the tail tip. Lip region continuous with the adjacent body, bearing three pairs of asymmetrical lips, one dorsal and two ventrolateral, six labial and four cephalic sensillae; primary axils deep, U-shaped, having one elongate triangular process originating from the incomplete first annulus; secondary axils with two guarding processes, each one originating from each lip; lips asymmetrical, each one with three setiform processes along its margin, the lateral ones longer than the median one; oral opening surrounded by three labial probolae, connected at bases by tangential ridges; each labial probola with a very short basal part, and a longer and bifurcated distal part, bearing very long, divergent and straight prongs that lack lateral tines and secondary bifurcations; the base of bifurcation is slightly expanded toward the secondary axil. Amphids clearly visible, large, oval. Stoma cephaloboid: cheilostom consisting of well-developed, oval rhabdia; gymnostom very short; and stegostom with minute rhabdia. Pharynx also cephaloboid: pharyngeal corpus 2.5 – 2.7 times isthmus length, with subcylindrical, posteriorly narrower procorpus, and elongate and dilated metacorpus with expanded lumen and sclerotized walls; pharyngeal corpus – isthmus junction slightly swollen at corpus and narrower at isthmus; isthmus slender, demarcated by a break in muscular tissue; basal bulb ovoid, with valvular apparatus. Cardia conoid, surrounded by intestinal tissue. Nerve ring at 72 – 79% of neck length, at level of isthmus. Excretory pore at 74 – 77% of neck length, at level of isthmus, 23 – 25 annuli from anterior end. Deirids at 88 – 94% of neck length, at level of bulb, 28 – 30 annuli from anterior end. Intestine without distinct specializations.

Female. Reproductive system monodelphic-prodelphic, dextral in relation to intestine. Ovary short, not reaching the distal part of postvulval sac, without flexures. Oviduct short. Spermatheca well developed, about equal to the corresponding body diameter in length. Uterus tubular, 1.8 – 1.9 times the corresponding body diameter long. Postvulval sac well developed, 2.1 – 2.3 times body diameter long, differentiated in two regions, a tubular proximal and another swollen distal. Vagina elongated forming a tube connecting uterus and postvulval sac. Vulval lips protruding. Rectum 0.7 – 1.1 times anal body diameter; three large gland-like cells are distinguishable around the intestine – rectum junction. Tail conical with finely rounded terminus. Phasmids located at 40 – 42% of tail length.

Male. General morphology similar to female. Reproductive system monorchic, dextral in position, with testis reflexed ventrad anteriorly. Spicules paired and symmetrical, very slender and curved ventrad: variably rounded manubrium, conoid calamus, and ventrad curved lamina with acute tip. Gubernaculum well developed, almost straight, about one half of the spicules length, lanceolate at its terminus. Three small gland-like cells are distinguishable around the beginning of the cloaca. Genital papillae as follows: three pairs precloacal, one adcloacal papilla, and five pairs caudal (one ventral, one lateral and three near tail terminus). Tail conical, curved ventrad, with acute tip. Phasmids located at 59% of tail length.

Distribution

Province of Almería, Salinas de Cabo de Gata, Cabo de Gata-Níjar Natural Park, near salt mine, in volcanic sandy soil, associated with Sarcocornia fruticosa (L.) Scott., Urginea maritima (L.) Baker and Lygeum spartum L.

Remarks

The population of P. psammophilus from Cabo de Gata (Almería, Spain) examined here is similar to the original material described by Navarro and Lluch (1999) from El Saler (Valencia, Spain), only differentiated by having shorter neck, and by the ranges of length for spicules and gubernaculum (see Table 3). Compared with the material described by Orselli and Vinciguerra (2002) from Italy, the specimens of the Spanish population examined here, like the type population, have a smaller size (shorter body length, pharyngeal corpus, spicules and gubernaculum) .

Nothacrobeles nanocorpus De Ley, De Ley, Baldwin, Mundo-Ocampo and Nadler, 1999

( Figures 4F – K , 6G – K , 7 )

Material examined

Four females and one male from two localities.

Morphometrics

See Table 1.

Description

Adult. Stout nematodes, body 0.20 – 0.24 mm long. Habitus straight to slightly curved ventrad. Cuticle annulated, annuli about 1.5 μm wide. Lateral field with two main and two outer and narrower wings, or five longitudinal incisures, the outer ones poorly visible under LM; only the central wings are present but fused (lacking the median incisures) behind the phasmids. Lip region continuous with the adjacent body, bearing six lips fused into pairs, and four cephalic and six labial sensillae; lips having smooth margin and divided at level of the labial sensilla; primary axils U-shaped and with two very small triangular guarding processes; secondary axils lacking guarding processes; three very low labial probolae, with neither prongs nor tines, and a basal ridge encircling each entire probola having a rounded concave shape. Amphid openings located to bases of lateral lips. Stoma cephaloboid, 0.6 – 0.9 times the lip region width long, and divided into cheilostom, gymnostom, and stegostom, the latter the longest. Pharynx also cephaloboid: corpus cylindrical, muscular, 0.9 – 1.0 times as long as the isthmus, with metacorpus clearly more muscularized than precorpus; isthmus long, very narrow, muscular; basal bulb pyriform, with striated transverse valves located anteriorly. Excretory pore opening at the level of isthmus posterior part, located at 66 – 75% of neck length, or at 26 – 31 annuli from anterior end. Deirids located at 73 – 88% of neck length, or at 36 annuli from anterior end. Cardia conoid, short. Intestine without differentiations.

Female. Reproductive system monodelphic, prodelphic, dextral in relation to intestine. Ovary reflexed at postvulval part, containing oocytes at different developmental stages. Oviduct short. Spermatheca swollen, short, 0.3 – 0.6 times the corresponding body diameter. Uterus 0.9 – 2.4 times the body width long, differentiated in a distal tubular part with thick walls, and a swollen proximal part with thin walls. Postvulval sac very short, 0.2 – 0.3 times the corresponding body diameter. Vagina extending inwards 25 – 36% of body diameter. Vulva not protruding. Rectum 1.0 – 1.4 anal body widths long. Tail conical, with 9 – 11 ventral annuli and finely rounded tip. Phasmids located at 50 – 59% of tail length.

Male. General morphology similar to female (unfortunately the specimen examined was broken before the measurements were obtained). Reproductive system monorchic, dextral in position, with testis reflexed ventrad anteriorly. Spicules paired and symmetrical, robust and slightly curved ventrad: more or less rounded manubrium, conoid calamus, and ventrad curved lamina with acute tip. Gubernaculum well developed, almost straight, about one half of spicules length. Three small gland-like cells are distinguishable around the cloacal anterior end. Precloacal genital papillae not well observed; postcloacal genital papillae five pairs, one lateral, one ventral, two subventral and one subdorsal. Tail conical, almost straight, visibly narrowing at its tip. Phasmids located at 48% of tail length.

Distribution

Species found in (i) Linares, province of Jaén, in soil from a garden with ornamental plants; and (ii) Salinas de Cabo de Gata, Cabo de Gata-Níjar Natural Park, province of Almería, near a salt mine, in volcanic sandy soil, associated with Sarcocornia fruticosa (L.) Scott., Urginea maritima (L.) Baker and Lygeum spartum L.

Remarks

The Iberian material of this species is very similar to the type material described by De Ley et al. (1999) from California. Nevertheless, some morphometric differences between both populations have been also noted (see Table 4): shorter body length (204 – 243 vs 240 – 295 μm), slightly longer stoma (5 – 6 vs 3 – 5 µm) and corpus – isthmus ratio (0.9 – 1.0 vs 0.5 – 0.9), slightly shorter isthmus (22 – 24 vs 26 – 34 µm long), neck (57 – 64 vs 65 – 77 µm long), spermatheca (4 – 8 vs 9 – 17 µm long) and postvulval sac (3 – 4 vs 8 – 15 µm long).

This is the first record of the male of this species, which is reported for the first time in the Iberian Peninsula and Europe.

Figures

Figure 4. Stegelleta ophioglossa Andrássy, 1967b (female): (A) neck region; (B) anterior region; (C) lateral field; (D) reproductive system; (E) posterior end. Nothacrobeles nanocorpus De Ley, De Ley, Baldwin, Mundo-Ocampo and Nadler, 1999: (F) lip region; (G) neck region; (H) female reproductive system; (I) lateral field; (J) female posterior end; (K) male posterior end.

Figure 5. Paracrobeles psammophilus Navarro and Lluch, 1999: (A) neck region; (B) lip region; (C) entire female; (D) female posterior end; (E) lateral field; (F) female reproductive system; (G) entire male; (H) male posterior end.

Figure 6. Paracrobeles psammophilus Navarro and Lluch, 1999 (LM): (A) neck region; (B) lip region (I = primary axil, II = secondary axil, black arrows point at labial processes, white arrows point at guarding processes); (C) female posterior end; (D) male posterior end; (E) female reproductive system; (F) lateral field. Nothacrobeles nanocorpus De Ley, De Ley, Baldwin, Mundo-Ocampo and Nadler, 1999 (LM): (G) neck region; (H, I) female posterior end; (J) male posterior end; (K) lateral field.

Figure 7. Nothacrobeles nanocorpus De Ley, De Ley, Baldwin, Mundo-Ocampo and Nadler, 1999 (SEM, female): (A, F) neck region (arrow points at excretory pore); (B, C) lip region at primary and secondary axils, respectively; (D) lateral field and vulva in lateral view; (E) vulva in ventral view; (G, H) posterior end in ventral and lateral views, respectively (arrow points at phasmid in H).