Myolaimus ibericus Abolafia & Peña-Santiago, 2016, sp. n.
Creators: name: Abolafia, Joaquín
name: Peña-Santiago, Reyes
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda
Chromadorea
Rhabditida
Myolaimidae
Myolaimus
Myolaimus ibericus

description: Myolaimus ibericus sp. n.
(Figs 1–6)
Material examined. Eighteen females and eleven males, mostly in good state of preservation.
Type locality and habitat. Spain, Jaén province, Jaén town, Puente de la Sierra (GPS coordinates: 37°42'36.5"N and 3°45'33.2"W, elevation 439 m), from domestic compost (pH = 7.11) in an orchard.
Type material. Sixteen females (holotype and paratypes) and nine males (paratypes) deposited with the Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Spain; and one female and one male (paratypes) deposited in the nematode collection of the Swedish Museum of Natural History, Stockholm (Sweden). Two specimens used for SEM study.
Morphometrics. See Table 1.
Description. Adult: Moderately slender to slender nematodes of small size, 0.56–0.78 mm long in females and 0.53–0.73 mm in males. Habitus often curved ventrad after killing and fixation. Cuticle finely annulated, usually appearing swollen and baggy, with detached median layer (cuticular sheath), especially upon fixation. Lateral field inconspicuous, observed as a longitudinal sigmoid wing under light microscope, occupying 14–28% of body width. Lip region with six low lips bearing ten (six labial plus four cephalic) setiform papillae, the cephalic papillae (two subdorsal and two subventral) longer than the labial ones. Amphidial apertures elliptical, occupying ca one-fourth of the corresponding body diameter, and located at one lip region diameter from the anterior end. Oral opening triradiate, with smooth margin. Stoma ca. three times as long as wide, twice as long as the lip region width, asymmetrical in lateral view and symmetrical in dorso-ventral view; it consists of two parts, the anterior one (cheilo-gymnostom) slightly longer than broad and with wide lumen, whereas the posterior one (stegostom) is distinctly narrower; cheilostom as long as wide, with concave refractive rhabdia, these thickened at their posterior end; gymnostom very short, with hemispheroid refractive rhabdia; stegostom tube-like, with non-refractive rhabdia, and surrounded by the pharyngeal collar; prostegostom anisomorphic in lateral view, joining gymnostom to produce dorsally a big tooth-like process and subventrally two (right and left) small tooth-like processes; mesostegostom with smooth walls; metastegostom with one dorsal and two subventral (right and left) valves (glottoid-like apparatus); telostegostom containing the dorsal gland opening and differentiated from the pharynx by a small fold of the lumen. Pharynx tripartite, panagrolaimoid, its walls joining the telostegostom and protruding to its lumen; pharyngeal corpus subcylindrical, 1.7–2.6 times the isthmus length, with weakly swollen metacorpus; isthmus robust, cylindrical; basal bulb pyriform, with distinct valvular apparatus at its middle. Cardia short, enveloped by intestinal tissue. Nerve ring surrounding the anterior part of isthmus, situated at 55–78% of the total neck length from the anterior end. Excretory pore near the metacorpus-isthmus junction, at 49–67% of the total neck length from the anterior end, with detached cuticle. Hemizonid not observed. Deirids located laterally close the excretory pore, at 55–61% of the total neck length from the anterior end, pore-like in females but seta-like in males.
Female: Reproductive system monodelphic, prodelphic, panagrolaimoid. Ovary antidromously reflexed, with oocytes arranged in two rows in its distal half but in a single row in its proximal part. Oviduct and uterus not clearly offset from each other, but the latter with thinner walls at its posterior half, often containing sperm and, more occasionally, only one egg with finely thorny shell. Post-uterine sac 1.7–2.7 times the corresponding body diameter long, frequently with sperm inside. Vagina equatorial or slightly posterior, perpendicular to body surface, and occupying one-third of the body dimeter. Vulva slightly protruding, with large, open, tube-like cuticular extension (vulval sac) variable in size, often bearing a copulatory plug. Intestine-rectum junction constricted by a sphincter. Rectum 1.8–2.7 times the anal body diameter long. Tail uniformly elongate-conical with acute tip. Phasmids inconspicuous, pore-like, located at 11–17% of tail length. Body often enveloped by the baggy cuticle at anus level.
Locality Puente de la Sierra
Province Jaén
Habitat Compost
Male: Testis reflexed (distal arm) for ca 40% of its length: spermatogonia, spermatocytes and spermatids arranged in two rows. Seminal vesicle swollen, with fine transverse septa. Vas deferens a thin tube lacking any differentiation. Spicules and gubernaculum absent. Cloaca tubular, 2.0–3.7 times the anal body diameter long, its opening having the anterior cloacal lip flap-like almost as wide as the corresponding body diameter in ventral view, acute laterally. Tail very short, conoid, slightly curved ventrad with rounded tip in lateral view, while constricted at phasmid level and with swollen end in ventral view. Male posterior end with a poorly developed bursa-like structure, anteriorly open and constricted at cloaca level, with seven pairs of genital papillae (4+1+2): three distinct pre-cloacal pairs (GP1 and GP2 inwardly directed and GP3 outwardly directed), one distinct ad-cloacal pair (GP4) inwardly directed, one distinct and slightly post-cloacal pair (GP5) outwardly directed, and two very small pairs (GP6 and GP7) at tail terminus and outwardly directed. In addition, there is a single mid-ventral papilla in front of the cloacal lip. Phasmids very small, situated behind GP5.
Remarks. This is the first record of the genus in the Iberian Peninsula (see Abolafia & Peña-Santiago 2001, Abolafia et al. 2011), as well as of the family Myolaimidae and the suborder Myolaimina.
Diagnosis. The new species is characterized by its 560–783 µm long body in females and 526–731 µm in males, cuticle often appearing swollen and baggy, lateral field with one longitudinal wing, lip region with six amalgamated lips having ten (6 + 4) setiform papillae, stoma consisting of a wider anterior chamber (cheilogymnostom) and a tubular posterior part (stegostom) separated by a well developed dorsal tooth and two small, lateral (one right and another left) teeth, glottoid apparatus-like structure appearing at metastom, pharyngeal corpus 1.7–2.6 times the isthmus length, excretory pore and deirids located at metacorpus level, deirids pore-like in females and seta-like in males, female reproductive system monodelphic-prodelphic with antidromous ovary, postuterine sac 1.7–2.7 times the corresponding body diameter long, V = 50–56, female rectum 1.3–2.0 times the anal body diameter long, female tail elongate-conical (54–70 µm, c = 9.9–13.1, c’ = 4.4–5.8) often enveloped by the baggy cuticle, male tail conoid (8–10 µm, c = 3.7–4.8, c’ = 58.4–73.1) and ventrally constricted at its middle, bursal structure with seven (4+1+2) pairs of genital papillae.
Relationships. Myolaimus ibericus sp. n. resembles M. amicitiae Andrássy, 1959, M. byersi Giblin-Davis, Kanzaki, De Ley, Williams, Schierenberg, Ragsdale, Zeng & Center, 2010, M. cotopaxus Bärmann, Fürst von Lieven & Sudhaus, 2009, M. heterurus Cobb, 1920, M. hortulanus Bärmann, Fürst von Lieven & Sudhaus, 2009 and M. xylophilus Bärmann, Fürst von Lieven & Sudhaus, 2009, all of them with similar body size and female tail length. It can be distinguished from M. amicitiae by its longer body (593–783 vs 467 µm in females and 526–731 vs 412 µm in males), stoma posterior part (behind the dorsal tooth) much narrower than the anterior part (vs both anterior and posterior parts of stoma with similar width), males with bursa-like structure with parallel (vs convergent) walls to body axis anteriorly. It differs from M. byersi in its stoma bearing the dorsal tooth projected anteriorly (vs laterally to ventrally), egg with wrinkled (vs spiny) shell, longer post-uterine sac (about twice as long as vs as long as the corresponding body diameter), and longer male tail (twice cloacal body width vs as long as wide in ventral view). From M. cotopaxus, it differs by having longer post-uterine sac (about twice as long as the corresponding body diameter vs as long as the corresponding body diameter), and male tail constricted (vs slightly constricted) when observed in ventral view. From M. heterurus, it differs in its stoma being equally broad in lateral and dorso-ventral views (vs narrower in lateral view) and lacking folds at metastegostom level (vs bearing a big fold, probably an artifact according to Bärmann et al. 2009), male tail (ventral view) constricted (vs not constricted) at its mid-length and with broadly (vs narrowly) rounded terminus, GP1–5 equally separate (vs GP3 and GP4 almost overlapping in lateral view), and GP6 and 7 poorly developed (vs well developed). It differs from M. hortulanus by its longer post-uterine sac (twice as long as vs as long as the corresponding body diameter), longer male tail (twice as long as wide vs as long as wide) and constricted (vs not constricted) at its middle when observed in ventral view, anterior cloacal lip flap-like and as wide as (vs one-half of) the anal body diameter in ventral view. From M. xylophilus, it differs in its slightly longer body (560‒783 vs 435‒537 µm in females and 526–731 vs 441– 572 µm in males), more anterior vulva position (V = 50-56 vs V = 59-64), male tail weakly (vs deeply) constricted when observed in ventral view and with small (vs well developed) papillae at its terminus), and longer male tail (c’ = 1.1‒1.4 vs 0.8‒0.9). From all these species, M. ibericus sp. n. also differs in the morphology of the stoma that bears a glottoid-like apparatus, which however has been observed in M. byersi by Giblin-Davis et al. (2010, Fig. 12) and is poorly developed in M. heterurus (cf. Cobb, 1920).
Etymology. The specific epithet is a Latin term referring to inhabitants of the Iberian Peninsula, where the new species was found.
Species n L a b c c̍ V Stoma Pharynx Excretory Post- Tail Country Reference
pory (%) uterine
sac/body
width
. amicitiae 1♀ 467 21.0 3.4 8.8 5.0 1 57? 13?**?? 53** Hungary 3, 5, 6
1Ƌ 412 20.7 3.6 44.0? —? 114**?? 9**
10ƋƋ 394—623 18.0—25.0 1 2.8—4.0 26.0—57.0 1 1.1—1.4 — 7—9 135—156 53—60 — 11—15
. dendrodipnis 8♀♀ 340—760 1 16.0—35.0 3.5—4.4 9.4—22.0 2.6* 55—60????? Germany 14
5ƋƋ 370—450 1 24.0—35.0 1 3.5—4.0 45.0—69.0 1 1.3* —?????
. goodeyorum? ♀♀ 850—970 1 21.0—24.0 1 4.7—4.8 9.7—10.6 5.0* 50—54 10* 161* 56*? 2.0—3.0 80* United 10
M. heterurus Kingdom?ƋƋ 700—750 1 23.0—25.0 1 4.4 50.0 1 0.9* —??? —?
M. heterurus 1Ƌ? 700 24.2 4.4 70.0** 1.1* —? 160?? 10** Dem. Rep. 16
Congo
M. heterurus? ♀♀ 850—1100 1 22.7—30.9 4.0—5.7 9.0—15.2 3.9* 50‒55 18* 159*? 1.7*? 54* Germany 18
?ƋƋ 550—770 1 22.6—30.83.7—4.6 43.5—71.00.8* —??? — 5*
. hermaphrodita 10♀♀ 451—540 15.0—27.0 1 3.5—4.0 14.0—20.0 1 2.1—3.4 59— 63 7—9 128—140 55—62 0.9* 25—35 Germany 7
1Ƌ???? 0.6*???? — 14*
. heterurus 1♀ 590 1 25.6** 4.3** 11.8** 4.7** 48 7** 130**?? 50** Texas, 8
USA 1Ƌ 580 1 25.2** 4.4** 36.3* 4.3** — 7** 126**? — 16**
. hortulanus 10♀♀ 528—810 14.0—22.0 1 3.8—5.3 10.0—17.0 1 2.7—4.8 50— 66 8—10 141—176 47—55 1.1* 43—72 Netherland 7
s 10ƋƋ 565—710 22.0—54.0 1 3.5—4.6 51.0— 0.3—1.1 — 8—10 131—163 51— 60 — 6—11 107.0 1
. ibericus sp. n. 18♀♀ 560—783 28.0—36.4 3.7—4.7 9.9—13.1 4.4—5.8 50— 56 11—16 131—173 49—67 1.7—2.7 54—70 Spain 19 10ƋƋ 526—731 29.2—40.6 3.7—4.8 58.4—73.1 1.1—1.4 — 10—17 124—150 56— 63 — 8—10
......continued on the next page Species n L a b c c̍ V Stoma Pharynx Excretory Post- Tail Country Reference
pory (%) uterine sac/body width
indicus 16♀♀ 460—610 1 18.0—23.0 1 3.8—4.5 7.1—9.7 5.3* 50—53 7* 116* 52* 0.7* 57* India 1
123**
10♀♀ 479—727 17.1—27.2 4.0—5.0 7.0—10.0 5.0—7.5 48— 58 8—10 113—152 55*? 0.5—0.9 60—85 India 17 9ƋƋ 360—478 20.0—26.13.4—3.9 46.8—79.61.0—2.0 — 6—7 99 —128? — 5—9
maupasi? ♀♀ 480—680 1 20.4—27.7 3.7—4.2 7.8—10.0 7.2* 52—56????? Germany 12
?ƋƋ 400—450 1 25.3—28.63.3—3.7 64.2? —??? —? 10♀♀ 490—600 1 23.1—29.13.9—4.1 8.4—9.3? 53—57????? Italy 13 10ƋƋ 450—590 1 26.0—37.63.4—4.3 58.0—90.41.0* —??? —?
rahmi? ♀♀ 1215—1310 16.0—18.0 1 4.9—5.0 65.0—67.0 1? 64—70????? Brazil 15
Cephalobus
bursifer
?ƋƋ????? —??? —?
stammeri 10♀♀ 1125—1529 23.7—28.3 5.1—6.2 7.5—14.4 6.8* 49—50 14* 204* 53*? 1.3* 84—162 Germany 11
10ƋƋ 957—1243 25.2—34.74.8—5.9 51.7—65.21.1* —??? — 13—22? ♀♀ 1120—1530 1 24.0—28.0 1 5.1—6.2 8.0—14.0 1 7.0—8.0 1 49—50???? 80—160 Hungary 4, 6***?ƋƋ 960—1240 1 25.0—35.0 1 4.8—5.9 52.0—65.0 1? —??? — 13—22
tepidus 1♀ 670 1 28.0 1 4.6 24.0 1 2.2 52 12-13 148? 1.0 28 Hungary 6
1Ƌ 480 1 23.0 1 3.7 47.0 1 1.6* —? 130? — 9
xylophilus 10♀♀ 435—537 15.0—18.0 1 3.3—3.9 9.0—16.0 1 2.3—4.0 59‒ 64 8—10 131—149 41-53 2.8* 32—56 Germany 7
10ƋƋ 441—572 21.0—27.0 1 3.4—4.1 48.0—82.0 1 0.8—0.9 — 8—9 125—140 42- 49 — 7—10
material
M. heterurus 21♀♀ 400—700 1 18.0—27.0 1 3.2—4.0 13.0—21.0 1 3.1—4.8* 55—62????? Germany 14
21ƋƋ 380—620 1 18.0—27.0 1 3.4—4.4 38.0—64.0 1? —??? ‒?? ♀♀ 400—860 1 18.0—30.0 1 3.2—4.8 7.0—21.0 1 4.0—7.0 1 48—57????? Hungary 2, 4, 5, 6?ƋƋ 380—620 1 18.0—31.0 1 3.0—4.4 38.0—80.0 1 1.2* —??? ‒?
Measurements from illustrations. ** Measurements calculated from other measurements. *** Measurements taken from the type description.? Measurements unknown. — Character absent.
Measurements with “0” or “.0” added, not appearing in the original descrition.
References: 1) Ali et al. (1970), 2) Andrássy (1958), 3) Andrássy (1959), 4) Andrássy (1996), 5) Andrássy (1984), 6) Andrássy (2005), 7) Bärmann et al. (2009), 8) Cobb (1920), 9) Giblin-Davis et al.
2010), 10) Goodey (1929, 1963), 11) Hirschmann (1952), 12) Hnatewytsch (1929), 13) Meyl (1954), 14) Paesler (1956), 15) Rahm (1928, 1929), 16) Schuurmans-Stekhoven & Teunissen (1938), 17)
Sufyan et al. (2014), 18) Weingärtner (1953), 19) Present paper.
Comments on the genus Myolaimus. The genus Myolaimus is a homogenous taxon (see Table 2), with many of its species being very similar to each other and difficult to distinguish. Useful characters for their identification are: stoma morphology, but special attention should be paid to it as its aspect significantly changes depending on the view (lateral, sublateral or dorso-ventral) from which it is observed; post-uterine sac length; female tail length; and male posterior end with particular emphasis on the arrangement of its genital papillae (Fig. 7). The genus includes fifteen valid species, some of them deficiently characterized:
Type species:
M. heterurus * Cobb, 1920
Other species:
M. amicitiae Andrássy, 1959 [emended name by Andrássy (1984)]
= M. amititiae Andrássy, 1959
M. byersi Giblin-Davis, Kanzaki, De Ley, Williams, Schierenberg, Ragsdale, Zeng & Center, 2010 M. cotopaxus Bärmann, Fürst von Lieven & Sudhaus, 2009 M. dendrodipnis Paesler, 1956
M. goodeyorum Andrássy, 1984
= M. heterurus apud Goodey (1929), Schuurmans-Stekhoven & Teunissen (1938), Weingärtner (1953) nec
Cobb (1920), op. Andrássy (1984)
= M. stiloides Weingärtner in Hirschmann, 1952, nomen nudum M. hermaphrodita Bärmann, Fürst von Lieven & Sudhaus, 2009 (emended name, unchangeable Latin adjective)
= M. hermaphroditus Bärmann, Fürst von Lieven & Sudhaus, 2009 M. hortulanus Bärmann, Fürst von Lieven & Sudhaus, 2009 M. ibericus sp. n.
M. indicus Ali, Farooqui & Suryawanshi, 1971
M. maupasi (Hnatewytsch, 1929) Sanwal, 1960
= Macrolaimus maupasi Hnatewytsch, 1929
= Myolaimus heterurus apud Meyl (1954), nec Cobb (1920), op. Bärmann et al. (2009) M. rahmi Sudhaus, 1977
= Cephalobus bursifer apud Rahm (1928), nec de Man (1876), op. Sudhaus (1977) M. stammeri Hirschmann, 1952
M. tepidus Andrássy, 2005
M. xylophilus Bärmann, Fürst von Lieven & Sudhaus, 2009
(*) Paesler (1956) described two morphological forms of Myolaimus heterurus, namely M. h. f. longicauda and M. h. f. brevicauda, both synonymized with the type species by Andrássy (1984). However, both forms do not agree well with the original description of the species provided by Cobb (1920) as noted by Bärmann et al. (2009). As Paesler’s material was poorly described and illustrated, it is not possible to characterize it with accuracy, for which reason it is herein regarded as inquirenda. Loof (1964) recorded M. heterurus from Venezuela but, unfortunately, no additional information about this material is available.
description: Published as part of Abolafia, Joaquín & Peña-Santiago, Reyes, 2016, Myolaimus ibericus sp. n. (Nematoda, Rhabditida, Myolaimidae) from southern Iberian Peninsula, with a key to species of the genus, pp. 365-380 in Zootaxa 4208 (4) on pages 366-378, DOI: 10.11646/zootaxa.4208.4.4, http://zenodo.org/record/208353