Ablechroiulus spelaeus, Abolafia, Joaquín & Peña-Santiago, Reyes, 2011

Abolafia, Joaquín & Peña-Santiago, Reyes, 2011, Ablechroiulus spelaeus sp. n. and A. dudichi Andrássy, 1970 from Andalucía Oriental, Spain, with a discussion of the taxonomy of the genus Ablechroiulus Andrássy, 1966 (Nematoda, Rhabditida, Rhabditidae), Zootaxa 2922, pp. 1-14 : 2-7

publication ID	https://doi.org/ 10.5281/zenodo.205409
DOI	https://doi.org/10.5281/zenodo.5680885
persistent identifier	https://treatment.plazi.org/id/03AAC439-FFA9-FF8F-E5EE-6858FCF50F96
treatment provided by	Plazi
scientific name	Ablechroiulus spelaeus
status	sp. nov.

Treatment

Ablechroiulus spelaeus sp. n.

( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A–C, 3, 6H)

Measurements. See Table 1 View TABLE 1 .

form: mean ± standard deviation (range).

Description. Adult: Moderately slender nematodes of medium size, 0.81–1.48 mm long. Habitus slightly curved ventrad after fixation. Cuticle 1.8–2.5 µm thick, nearly smooth or with very fine transverse striations under LM, but which are more distinct on inner layer; annules 1.2–2.5 µm wide under SEM. Lateral field usually barely discernible under LM, 14 µm wide or about one-fourth of mid-body diameter. Lip region continuous with adjacent body or very slightly offset by a shallow depression, about three times as wide as high and one-third to two-fifths of body diameter at neck base (pharynx–cardia junction); lips separate, rounded, bearing small thin cirri-like setae, arranged in two groups of three each at the base of each lip. Stoma rhabditoid, 3.4–5.2 times longer than wide, 1.8– 2.7 times the lip region width, and 11–14% of neck length; cheilostom short, lacking refringent cheilorhabdia; gymnostom longer than cheilostom and with curved walls; stegostom more or less cylindrical, occupying about 60% of stoma length, often collapsed due to fixation; metastegostom bearing glottoid apparatus provided with three minute denticles in each lobe. Pharyngeal corpus 73–92 µm long, comprising 50-55% of pharynx length, with cylindrical procorpus and metacorpus, both well developed; isthmus 40–48 µm long, comparatively wide but distinctly narrower than corpus; basal bulb ovoid, 32–38 µm long, with valves located at its middle and a well developed haustrulum at posterior region. Cardia hemispherical, surrounded by intestinal tissue. Intestine lacking special differentiations, but showing thinner walls at cardiac region. Nerve ring at 104–124 µm, or 57–64% of neck length, from anterior end, surrounding the isthmus. Excretory pore located at 120–164 µm, or 68–80% of neck length, from anterior end, at level of posterior portion of isthmus. Deirid not well observed in the specimens examined.

Female: Reproductive system didelphic-amphidelphic, with both branches well and equally developed. Ovaries 131–350 µm long, the anterior one at right side of intestine and the posterior one at left side, each with a flexure, the reflexed distal part 63-96% of its total length. Oviducts 48–92 µm long or 1.3–1.7 times the corresponding body diameter: the proximal section wider than the distal one, both constituting an axial spermatheca, the latter bearing a more or less developed sac, or adaxial spermatheca; spermatocytes and spermatid cells are present. A distinct sphincter, consisting of several cells, separates oviduct and uterus. Uterus a simple, tube–like structure, 37–81 µm long or 1.0–1.7 times the corresponding body diameter, the thickness of its wall tapering near the vagina. Uterine eggs 50– 66 x 32–36 µm (n=3); if they are present, appearing singly at anterior uterus and close to vagina. Vagina extending inwards 10–18 µm or about one-third of body diameter, with thin walls. Vulva a transverse slit; its lips slightly elevated. Rectum curved, 0.7–1.3 anal body diameter long. Rectal glands small. Tail consisting of two parts: the anterior portion rounded, 10–16 µm long, and the posterior part filiform, 36–44 µm long, 2.4–4.4 times as long as the anterior portion and occupying 71–82% of total tail length, 1.9-2.7 times anal body diameter. Phasmid located at level of junction between the two parts of the tail, at 10–18 µm from anus.

Male: Reproductive system monorchic. Testis reflexed ventrad, at right side of intestine. Tail in two sections: anterior one conical and 23, 24 Μm long, and posterior part filiform, 29, 34 µm long, or 1.3, 1.4 times as long as anterior portion and occupying 56, 59% of total tail length. Bursa leptoderan, open anteriorly; nine pairs of genital papillae (1+2/1+2+3), three precloacal, the fourth and the seventh ones not reaching the margin of bursa and open on the dorsal side of the velum. Phasmids not clearly observed. Spicules fused, 1.5 times the cloacal body diameter in length, nearly straight, curved ventrad only at the posterior end; manubrium rounded and offset by a constriction (calamus), and lamina practically straight and with a terminal protuberance. Gubernaculum 50-54% of spicule length, slightly curved ventrad, and distally thinner.

Diagnosis. Ablechroiulus spelaeus sp. n. is characterized by having body length 0.81–1.48 mm in females and 0.74–1.20 mm in males, lip region nearly continuous and 9–13 μm wide, stoma 23–29 µm long or 1.8–2.7 times the lip region width, neck 166–265 μm long, metacorpus well differentiated, oviduct with a small sac, V = 55–59, female tail (51–60 µm, c = 14–25, c' = 1.9–2.7) with two marked sections, male tail (52, 58 µm, c = 14.3, 20.7, c' = 2.0) with filiform posterior part, bursa leptoderan and with nine pairs of papillae (1+2/1+2+3), spicules 40, 44 µm long having a terminal protuberance, and gubernaculum 20, 24 µm long.

Relationships. In having the female tail with two marked sections - the anterior one short and rounded and the posterior one very slender to filiform - this new Ablechroiulus species is very close to a group of three species, namely A. anchisporus Andrássy, 1966 , A. castaneanus Abolafia & Peña-Santiago, 2009 and A. ciliatus ( Fuchs, 1931) Andrássy, 1966 . A. spelaeus n. sp. differs from A. anchisporus , known to occur only in Ghana, in its relatively larger size (vs L = 0.79–1.04 in females, n = 6), more slender body (vs a = 18–24), relatively wider stoma (vs 4–5 μm), more posterior vulva (vs V = 51–55), and shorter tail (vs c = 6.2–11.0 in females and c = 11.8–13.7 in males) with a distinctly shorter posterior filiform section (vs 81–85% of total tail length), and bursal papillae GP4 separated from GP5 and GP6 (vs bursal papillae GP4, GP5 and GP6 close together); from A. castaneanus in its larger body size (vs L = 0.69–0.80 in females and L = 0.58–0.76 in males, stoma 18–20 µm long, n = 5), lip region continuous (vs offset by constriction), metacorpus well developed (vs scarcely differentiated), longer spicules (vs 21–25 µm long) and gubernaculum (vs 10–15 μm long); from A. ciliatus in its larger body size especially in males (vs L = 0.88–0.93), lip region continuous (vs offset by constriction), female tail more slender (vs c' = 1.0), and spicules with rounded manubrium and lamina with a terminal protuberance (vs manubrium and lamina tip lobed).

Type locality and habitat. The new species was found in a natural cave named Cueva del Jabalí, in Santiago- Pontones, Sierras de Cazorla, Segura y las Villas Natural Park, province of Jaén, where it was associated with bat excrement.

Type material. Female holotype, four female and two male paratypes deposited with the nematode collection of Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Spain. One female paratype deposited at USDANC, Beltsville, MD, USA. [One female paratype was used for SEM study].

Etymology. The specific epithet is a Latin term meaning ‘from caves’ and refers to the place where the species was collected.

Remarks. In spite of the fact that differences between the new species and its closest relatives are morphometric (mainly body length, stoma length and width, vulva position, female tail length) and based on the study in general of only a few specimens, there are significant gaps in the ranges of several measurements and ratios to support the separation of the proposed new taxon from them.

This is the second record of Ablechroiulus representatives in caves, after the finding of A. ciliatus in Ukraine ( Holovachov, 2004).

The new species is the fourth one belonging to the genus Ablechroiulus collected in a natural, protected area in the southeastern Iberian Peninsula (see Abolafia & Peña–Santiago, 2009).

Ablechroiulus dudichi Andrássy, 1970 ( Figs. 2 View FIGURE 2 D, 4)

= Rhabditis dudichi ( Andrássy, 1970) Sudhaus, 1976

= Rhabditis (Choriorhabditis) dudichi ( Andrássy, 1970) Sudhaus & Kühne, 1990

Measurements. See Table 1 View TABLE 1 .

Description. Female: Moderately slender nematodes of small size, 0.66 mm long. Habitus after fixation nearly straight. Cuticle smooth under LM, 1.0 µm thick. Lip region continuous with the adjacent body, 2.5 times as wide as high and about one-third (33%) of body diameter at neck base; lips rounded, apparently separate and bearing tufts of two thin and long cirri-like setae when observed under LM. Stoma rhabditoid, nearly eight times as long as wide, 2.6 times as long as lip region diameter and 3.5% of body length: cheilostom wide, lacking refractive rhabdia; gymnostom as wide as long, and slightly longer than cheilostom; stegostom cylindrical, narrow; metastegostom bearing glottoid apparatus with minute teeth in subventral lobes and larger tooth in the dorsal one. Pharyngeal corpus 66 µm long, consisting of cylindrical procorpus and swollen metacorpus, the former about 2.5 times longer than the latter; isthmus 34 µm long, tapering gradually from metacorpus to its junction with basal bulb; basal bulb ovoid, 27 µm long, with three valves in its anterior half. Cardia very small and surrounded by intestinal tissue. Nerve ring at 103 µm, or 67% of neck length, from anterior end, located around the anterior half of isthmus. Excretory pore at 124 µm, or 81% of neck length, from anterior end, situated at level of the posterior part of the isthmus. Deirid at 132 µm, or 86% of neck length, from anterior end, at level of basal bulb. Reproductive system didelphic– amphidelphic, numerous coelomocytes appearing around it: ovaries 112–120 µm long, each with a flexure, the reflexed portion slightly longer than the outstretched one; oviducts 32–44 µm long or 1.2–1.7 times longer than the corresponding body diameter, with the proximal section swollen with sperm cells; a marked constriction separates spermatheca and uterus; uterus tubular, 1.1–1.2 times the body diameter long; vagina 10 µm long, extending inwards one–third of body diameter, with thin walls; vulval lips visibly protruding. Tail long and filiform. Phasmid at 11% of tail length.

Male: Not found.

Locality and habitat. Navarra, in soil of an oak forest with Quercus robur L., Crataegus monogyna Jacq. , and Rubus sp.

Remarks. The above description is based on a single female found at the sampling locality. Its morphometric features perfectly agree with those of the type population, but the lip region is wider (9 vs 7 µm in the Vietnamese type population) and, in consequence, the stoma relatively shorter (2.6 vs 3.3–3.4 times the lip region width in the type material, although in the original illustration ( Andrássy, 1970: Fig. 4 View FIGURE 4 A) it is only about 2.7). This specimen is tentatively considered to be conspecific with the Vietnamese ones.