Stegelleta Thorne 1938
Creators: name: Boström, Sven
name: Holovachov, Oleksandr
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda
Secernentea
Rhabditida
Cephalobidae
Stegelleta
Stegelleta incisa
Stegelleta laterocornuta
Stegelleta ophioglossa
Stegelleta tuarua

description: Genus Stegelleta Thorne, 1938
Stegella Thorne, 1937: 4 [junior homonym of Stegella Stechow, 1919].
Stegelleta Thorne, 1938: 64–65.
Type species
Stegella incisa Thorne, 1937.
Diagnosis (emended after Holovachov et al. 2009)
Cuticle annulated, without distinctly annulated internal layer; annuli with longitudinal incisures (tessellated). Lateral field with two or four wings (appearing as three, four or five incisures); ending at tail terminus in females and in males. Lip region weakly offset, consisting of six globular lips arranged in three pairs: one dorsal and two subventral. Pairs of lips separated by primary axils; guarding processes absent; secondary axils undeveloped. Cephalic probolae absent or in the shape of one acute tine extending along the primary axil occurring only on lateral lips or on all six lips. Labial probolae elongate-conoid with broad basis, bifurcated about halfway forming two slender prongs, in some species further bifurcated apically. Six labial and four cephalic papilliform sensilla arranged in a cephaloboid manner. Amphidial aperture slit-shaped, located on lateral lips. Stoma divided into cheilo-, gymno- and stegostom: cheilostom barrel-shaped with strongly sclerotized bacilliform cheilorhabdia; gymnostom weakly developed, as wide as stegostom, with weak gymnorhabdia; stegostom consists of a funnel-shaped prostegostom and variably shaped mesostego-, metastego- and telostegostom parts. Metastegostom denticle present. Pharynx cephaloboid: pharyngeal procorpus and metacorpus cylindrical, lining of procorpus and metacorpus are of same thickness; isthmus narrower than metacorpus; basal pharyngeal bulb oval, with strongly developed valves. Nerve ring encircling posterior part of metacorpus or anterior part of isthmus. Excretory pore opens at level of nerve ring, at posterior part of metacorpus or anterior part of isthmus. Deirids present. Female reproductive system cephaloboid; posterior part of ovary straight; spermatheca present; postvulval uterine sac present; vagina straight; vulva flat, vulval flap absent or present. Male reproductive system cephaloboid; spicules cephaloboid with manubrium and corpus of approximately equal width; gubernaculum plate-like or wedge-shaped; cornua crurum present. Male genital papillae: at least one ventrosublateral pair located anterior to cloaca; one ventrosublateral pair located at the level of cloacal opening; two pairs located at middle of tail length; and three pairs (lateral, subventral and subdorsal) near tail terminus; there is a midventral papilla on anterior cloacal lip. Rectum short (1–2 times longer than anal body diameter). Phasmids located at about one-third to half of tail length in both sexes. Female tail conoid or subcylindrical, straight, tail terminus bluntly rounded or truncate; male tail conoid, arcuate ventrad, tail terminus bluntly rounded.
Valid species
Stegelleta arenaria Boström & Holovachov, 2012
Stegelleta georgica Bagaturija, 1973
Stegelleta iketaia Yeates, 1967
Stegelleta incisa (Thorne, 1937)
Stegelleta ophioglossa Andrássy, 1967
= Stegelleta cylindrica Mavljanov, 1978: 1889, figs 1–6
Stegelleta tuarua Yeates, 1967
Stegelleta incisa (Thorne, 1937)
Figs 1A–E, 2, Table 1
Stegella incisa Thorne, 1937: 14–15, fig. 4G–I.
Stegelleta incisa – Thorne 1938: 65.
Stegelleta ophioglossa – Orselli & Vinciguerra 2002: 216–219, figs 5, 6A–C.
Diagnosis
Stegelleta incisa is characterised by a 465–580 µm long body in females and 428–600 µm in males; cuticle divided by regular longitudinal striations into 16 rows of blocks at midbody (excluding lateral field); lateral field with four incisures extending almost to tail terminus in females and to midtail papillae in males, two outer incisures extend to tail terminus in males; three pairs of asymmetrical lips, pairs of lips separated by U-shaped primary axils without guarding processes, secondary axils demarcated by a shallow incisure, each lip asymmetrically rectangular with a smooth margin and without tines; three labial probolae, bifurcated at half of their length, prongs bent toward one another apically, “snaketongue”-shaped; pharyngeal corpus 2.1–2.9 times isthmus length; nerve ring and excretory pore at level of metacorpus to metacorpus-isthmus junction, deirids at level of metacorpus-isthmus junction to isthmus; vulva with anterior flap; spermatheca 24–43 µm long; postuterine sac 22–36 µm long; spicules 22–36 µm long.
Material examined
USA: 13 ♀♀, 9 ♂♂, SMNH 135940–135942, 28 Mar. 2010, California, Mojave National Preserve, Kelso Dunes, soil around roots of desert plants (34°53.698’ N, 115° 42.155’ W and 34° 53.754’ N, 115° 42.248’ W), legit O. Holovachov & P. De Ley.
Description
Adult
Body slightly arcuate in different ways when killed by heat, males often strongly arcuate ventrad in tail end. Cuticle coarsely annulated, annuli 2.4–3.4 µm wide at midbody and 2.2–3.0 µm wide in pharyngeal region. Cuticle tessellated: longitudinal striae giving it a tiled appearance, each block often with a central indentation as seen under SEM. Anteriorly, 9–10 first annuli, the longitudinal striation is irregular and blocks rounded, followed by a more regular striation creating rectangular blocks, 16 rows of blocks at midbody (excluding lateral field). Lateral field consisting of two wings separated by a broad groove, appearing as four incisures under LM, occupying about 20–25% of body diameter, extending almost to tail terminus in females and to midtail papillae in males, two outer incisures extend to tail terminus in males. Lip region slightly offset, carrying 6 + 4 papillae and two round amphids. Three pairs of asymmetrical lips, one dorsal and two ventrolateral. Pairs of lips separated by U-shaped primary axils without guarding processes. Each pair with a shallow incisure demarcating a secondary axil. Each lip asymmetrically rectangular with a smooth margin, without any tines. Three labial probolae, 8.0– 9.5 µm high, bifurcated at half of their length, prongs bent toward one another apically (“snake-tongue”-shaped). Stoma somewhat longer than lip region diameter. Stomatal parts not clearly discernible. Cheilorhabdia bacilliform in lateromedian view; metastegostom with a dorsal denticle. Pharynx cephaloboid. Pharyngeal corpus cylindrical; isthmus narrow, often folded, and not clearly demarcated from corpus; bulb oval, with valves. Nerve ring at level of metacorpus to metacorpus-isthmus junction. Excretory pore and deirids at level of metacorpus-isthmus junction to isthmus.
Female
Reproductive system monodelphic, prodelphic, in dextral position in relation to intestine. Ovary reflexed posteriorly at oviduct, ovary straight posterior to vulva. Spermatheca well developed. Postvulval uterine sac one to one-and-a-half times vulval body diameter long. Vagina about one-third of vulval body diameter. Vulval lips not or slightly protruding, anterior lip with cuticular flap directed posteriad and partly covering vulval opening. Vulva covered by genital plug in some specimens. Tail conoid with 13–15 ventral annuli, terminus truncate. One specimen has a tail with only 10–11 annuli and broadly rounded terminus. Phasmids located at about one-third to half of tail length.
Male
Reproductive system monorchic, dextral in position; testis reflexed ventrad anteriorly. Spicules paired and symmetrical, curved ventrad; with oval manubrium and subcylindrical, gradually narrowing shaft. Gubernaculum plate-like, cornua crurum present. Tail strongly arcuate ventrad, conoid with rounded terminus. The two outer lateral lines extend posterior to the phasmid, transforming into a cuticular ridge that reaches tail terminus. Genital papillae arranged as follows: two pairs subventral precloacal (at 24–33 µm and at 42–58 µm anterior to cloaca), one pair subventral adcloacal, a single midventral papilla on anterior cloacal lip; two pairs (one ventrosublateral and one lateral) at midtail; three pairs (one lateral, one subventral and one dorsosublateral) closer to tail terminus. Phasmids located at about two-fifths to half of tail length.
Remarks
The population collected from sand in the Kelso Dunes area, Mojave Desert, California and described here, agrees in many respects with the type specimens of Stegelleta incisa described from Utah by Thorne (1937) and a bisexual population described from Italy by Orselli & Vinciguerra (2002) under the name S. ophioglossa. One major difference is the presence of a cuticular flap on the anterior vulval lip directed posteriad and partly covering the vulval opening, as seen by SEM in the present specimens. This feature is not easily seen with light microscopy, which probably explains why it was not mentioned by Thorne (1937) in his original description. Orselli & Vinciguerra (2002) also did not mention or illustrate it in their specimens, presumably for the same reason.
Stegelleta laterocornuta sp. nov.
urn:lsid:zoobank.org:act: 7669B17A-D71A-46C0-8BA0-EB92F28B7111
Figs 1F–J, 3, Table 2
Stegelleta sp. JB-75 – Nadler et al. 2006: 701, table 1.
Diagnosis
Stegelleta laterocornuta sp. nov. is characterised by a 379–512 µm long body in females and 365–476 µm in males; cuticle divided by regular longitudinal striations into 16 rows of blocks at midbody (excluding lateral field); lateral field with four incisures extending almost to tail terminus in females and to midtail papillae in males, two outer incisures extend to tail terminus in males; three pairs of asymmetrical lips, pairs of lips separated by U-shaped primary axils without guarding processes, secondary axils demarcated by a shallow incisure, each lip asymmetrically rectangular with a smooth margin, only lateral lips have slender acute tines; three labial probolae, bifurcated at half of their length, prongs bent toward one another apically, “snake-tongue”-shaped; pharyngeal corpus 2.3–3.0 times isthmus length; nerve ring and excretory pore at level of metacorpus to metacorpus-isthmus junction, deirids at level of isthmus; vulva without flap; spermatheca 17–31 µm long; postuterine sac 7–24 µm long; spicules 21.5–23.5 µm long.
Etymology
The species name is derived from the Latin lateris (= side) and cornu (= horn), referring to the long acute tine extending along the primary axil on the lateral lips.
Material examined
NEW ZEALAND: holotype ♀, paratypes 13 ♀♀ and 9 ♂♂, SMNH Type-8602, 1999, South Island, Tasman District, Abel Tasman National Park, legit Christine (Gamble) Powell, cultured as the strain Stegelleta sp. JB-75.
Description
Adult
Body slightly arcuate in different ways when killed by heat, males often strongly arcuate ventrad in tail end. Cuticle coarsely annulated, annuli 1.9–2.7 µm wide at midbody and 2.0– 2.4 µm wide in pharyngeal region. Cuticle tessellated: longitudinal striae giving it a tiled appearance, 16 rows of blocks at midbody (excluding lateral field). Lateral field consisting of two wings separated by a broad groove, appearing as four incisures under LM, occupying about 20–25% of body diameter, extending almost to tail terminus in females and in males. Lip region slightly offset, carrying 6 + 4 papillae and two round amphids. Three pairs of asymmetrical lips, one dorsal and two ventrolateral. Pairs of lips separated by U-shaped primary axils without guarding processes. Each pair with a shallow incisure demarcating a secondary axil. Each lip asymmetrically rectangular with a smooth margin. Lateral lips only with long, slender, acute tine extending along the primary axil. Three labial probolae, 7.0– 8.5 µm high, bifurcated at half of their length, prongs bent toward one another apically (“snake-tongue”-shaped). Stoma somewhat longer than lip region diameter. Stomatal parts not clearly discernible. Cheilorhabdia bacilliform in lateromedian view; metastegostom with a dorsal denticle. Pharynx cephaloboid. Pharyngeal corpus cylindrical; isthmus narrow, often wrinkled, and not clearly demarcated from corpus; bulb oval, with valves. Nerve ring and excretory pore at level of metacorpus-isthmus junction to isthmus. Deirids generally at level of isthmus.
Female
Reproductive system monodelphic, prodelphic, in dextral position in relation to intestine. Ovary reflexed posteriorly at oviduct, ovary straight posterior to vulva. Spermatheca well developed. Postvulval uterine sac about half to one-and-a-half times vulval body diameter long. Vagina about one-third of vulval body diameter. Vulval lips not or slightly protruding, without flaps. Vulva with genital plug seen in one specimen. In four females one intrauterine egg each was found, measuring 36–57 x 14.5–15.5 µm. Tail conoid with 16–22 ventral annuli, terminus broadly rounded or truncate. Phasmids located at about onethird to two-fifths of tail length.
Male
Reproductive system monorchic, dextral in position; testis reflexed ventrad anteriorly. Spicules paired and symmetrical, curved ventrad; with oval manubrium and subcylindrical, gradually narrowing shaft. Gubernaculum plate-like, cornua crurum present. Tail strongly arcuate ventrad, conoid with rounded terminus. The two outer lateral lines extend posterior to the phasmid, transforming into a cuticular ridge that reaches tail terminus. Genital papillae arranged as follows: two pairs subventral precloacal (at 4–6 µm and at 23–28 µm anterior to cloaca), one pair subventral adcloacal, a single midventral papilla on anterior cloacal lip; two pairs (one ventrosublateral and one lateral) at midtail; three pairs (one lateral, one subventral and one dorsosublateral) closer to tail terminus. Phasmids located at about two-fifths to half of tail length.
Remarks
The population of Stegelleta laterocornuta sp. nov. from New Zealand described here agrees in many respects with the descriptions of S. incisa. One major difference is the presence of a long, slender and acute tine extending along the primary axil on the lateral lips. This is a somewhat intermediate stage between S. incisa, which has no tines, and S. arenaria, in which each lip has one acute tine extending along the primary axil. Another difference is the absence of a cuticular flap on the anterior vulval lip, as seen by SEM in the specimens of S. incisa from California.Stegelleta laterocornutasp. nov.Stegelleta tuaruaPopulationNew Zealand JB-75Type population populationCastlecliffNo. & sexHolotype14 ♀♀ (incl. holotype)9 ♂♂ {1 aberr.}1 ♀3 ♂♂2 ♂♂Body length433 ± 41 428 ± 35 447 (379–512) (365–476) 19.1 ± 1.7 17.4 ± 1.1 20.5 (15.5–21.5) (15–19) 116.7 ± 5.2 117.8 ± 4.6 118 (109–126) (109–123) {138} 35.9 ± 2.9 24.2 ± 0.9 38 (30–42) (22–25) {36} 11.1 ± 0.8 11.9 ± 0.4 11 (9.5–12.5) (11.0–12.5) {13} 270 ± 22 223 ± 15 273 (235–315) (200–235) 3.6 ± 0.3 3.6 - (3.0–3.9) 22.7 ± 1.7 24.6 ± 1.3 21.8 (18.6–26.0) (21.5–26.5) 3.7 ± 0.3 3.6 ± 0.2 3.8 (3.4–4.3) (3.3–4.0) 12.1 ± 0.7 17.7 ± 1.4 11.8 (10.5–13.0) (15.2–19.8) {13.1} 3.2 ± 0.2 2.0 ± 0.1 3.5 (2.7–3.6) (1.8–2.2) {2.8} 62.3 ± 1.2 54.2 ± 3.7 61 (60–65) (49–60) 6.8 ± 0.4 6.7 ± 0.4 7.0 (6.5–8.0) (6–7) 8.9 ± 0.3 8.7 ± 0.5 9.0 (8.5–9.5) (8.0–9.5) 69.6 ± 4.1 69.6 ± 1.9 70 (63–75) (66–72) {81} 26.7 ± 2.3 27.1 ± 1.7 26 (24–30) (24–29) {36} 14.8 ± 1.0 14.3 ± 0.7 14.5 (13–17) (13.0–15.5) {17} 11.5 ± 0.7 11.0 ± 0.7 11 (10–13) (10–12) 2.6 ± 0.2 2.6 ± 0.2 2.7 (2.3–3.0) (2.4–2.9) {2.3} 83.0 ± 7.7 86.6 ± 6.4 92 (70–96) (77–96) {102} 635 563–739 650; 688Body diameter (BD)- - 45; 46Pharynx length- - 144; 165Tail length- - 43; 48Anal or cloacal diam. (ABD)- - 30; 30Vulva or Testis- - 432; 476V-A/T- - -a21.2 17.2–18.8 14.4; 15.0b3.8 3.9–4.8 4.5; 4.2c25.4 14.1–16.0 15.1; 14.3c’1.6 1.6–1.9 1.4; 1.6V or T (%)69.2 56.8–62.7 66; 69Lip region diameter- - 11; 12Stoma length- - 14.5; 19Corpus length- - 92; 110Isthmus length- - 22; 20.5Bulb length- - 23; 24Bulb diameter- - 19; 20.5Corpus/isthmus ratio- - 4.2; 5.4Nerve ring from ant. end- - 108; 121Stegelleta laterocornutasp. nov.Stegelleta tuaruaPopulationNew Zealand JB-75Type populationCastlecliffNo. & sexHolotype14 ♀♀ (holotype incl.9 ♂♂ {1 aberr.}) incl.9 ♂♂ {1 aberr.})1 ♀3 ♂♂2 ♂♂Excretory pore from ant. end 86.3 ± 8.1 94 (72–97) 92.0 ± 6.6 (81–99) {106} -- ?; 130Deirid from ant. end100 92.9 ± 7.2 (81–104) 100.2 ± 5.6 (89–105) {107} - - 141; 171RNR*42 35 ± 4 35 ± 2 (28–42) (32–39) {47} - - 35; 38REP*37 ± 4 37 ± 2 43 (32–43) (33–39) {49} - - ?; 41RDEI*46 40 ± 4 (35–48 ) 42 ± 2 (37–44) {50} - - 46; 55Annuli width at midbody2.7 2.0–2.7 2.0–2.7 - - 2.4; 2.4Annuli width anteriorly2.0 2.0–2.4 2.0–2.4 - - 3.0–3.4; 3.0–3.4 Vagina or Testis flexure length 6.0 ± 0.6 39.8 ± 3.9 6.0 (5–7) (35–46) -- 90 (dors); 82Spermatheca or Spicule length 20.6 ± 4.6 22.5 ± 0.7 18 (17–31) (21.5–23.5) - 36–4043; 42PUS or Gubernaculum length 18.1 ± 5.9 11.4 ± 0.5 17 (7–24) (11–12)- 21–24 25; 24PUS/VBD1.0 ± 0.3 0.9 - (0.6–1.3) - - -Rectum16.6 ± 1.1 17 - (15.5–19.0) - - -Rectum/ABD1.5 ± 0.1 1.5 - (1.4–1.6) - - -Phasmid11.6 ± 0.7 10.6 ± 1.1 12 (10–13) (8.5–12.0) {18} - - 18; 18Phasmid (% of tail)32 32.2 ± 1.7 44.0 ± 3.6 (30–37) (38–50) - ~40 42; 38
Stegelleta ophioglossa Andrássy, 1967
Fig. 4A–D, Table 3
Stegelleta ophioglossa Andrássy, 1967: 208–210, fig. 3.
Diagnosis
Stegelleta ophioglossa is characterised by a 315–490 µm long body in females; cuticle divided by regular longitudinal striations into 12–16 rows of blocks at midbody (excluding lateral field); lateral field with four incisures extending almost to tail terminus in females; three pairs of asymmetrical lips, pairs of lips separated by U-shaped primary axils without guarding processes, secondary axils demarcated by a shallow incisure, each lip asymmetrically rectangular with a smooth margin and without tines; three labial probolae, bifurcated at half of their length, prongs bent toward one another apically, “snaketongue”-shaped; pharyngeal corpus 3–5 times isthmus length; nerve ring, excretory pore and deirids at level of isthmus; vulva without flap; spermatheca 7–13 µm long; postuterine sac 7–17 µm long.
Material examined
SENEGAL: 6 ♀♀, SMNH 135943–135944, Kaolack region, Thyssé-Kaymor, legit C. Villenave.
Description
Adult
Body slightly arcuate ventrad when killed by heat. Cuticle annulated, annuli 1.6–2.2 µm wide at midbody and 1.7–2.0 µm wide in pharyngeal region. Cuticle tessellated: longitudinal striae giving it a tiled appearance, 16 rows of blocks at midbody (excluding lateral field). Lateral field consisting of two wings separated by a narrow groove, appearing as four incisures under LM, occupying about 20% of body diameter, extending almost to tail terminus in females. Lip region slightly offset, carrying 6 + 4 papillae and two round amphids. Three pairs of asymmetrical lips, one dorsal and two ventrolateral. Pairs of lips separated by U-shaped primary axils without guarding processes. Each pair with a shallow incisure demarcating a secondary axil. Each lip asymmetrically rectangular with a smooth margin. Three labial probolae, 6–7 µm high, bifurcated at half of their length, prongs bent toward one another apically (“snake-tongue”-shaped). Stoma somewhat longer than lip region diameter. Stomatal parts not clearly discernible. Cheilorhabdia bacilliform in lateromedian view; metastegostom with a dorsal denticle. Pharynx cephaloboid. Pharyngeal corpus cylindrical; isthmus narrow, not clearly demarcated from corpus; bulb oval, with valves. Nerve ring, excretory pore and deirids at level of isthmus.
Female
Reproductive system monodelphic, prodelphic, in dextral position in relation to intestine. Ovary reflexed posteriorly at oviduct, ovary straight posterior to vulva. Spermatheca small, not developed. Postvulval uterine sac short, about one-half of vulval body diameter long. Vagina about one-third of vulval body diameter. Vulval lips not protruding. Tail conoid with 12–20 ventral annuli, terminus truncate. Phasmids located at about one-fourth to one-third of tail length.
Male
Not found.
Remarks
The specimens described here agree in many respects with the population of Stegelleta ophioglossa from Senegal described by De Ley et al. (1990) and several other populations of S. ophioglossa (Andrássy 1967; Mavljanov 1978; Shokoohi et al. 2008; Abolafia et al. 2011).
Stegelleta tuarua Yeates, 1967
Fig. 4E–G, Table 2
Stegelleta tuarua Yeates, 1967: 536–538, fig. 5.
Diagnosis
Stegelleta tuarua is characterised by a 635 µm long body in females and 563–739 µm in males; cuticle divided by regular longitudinal striations into 40–44 rows of blocks at midbody; lateral field with five incisures extending almost to tail terminus in females and in males; three pairs of asymmetrical lips, pairs of lips separated by U-shaped primary axils without guarding processes, secondary axils demarcated by a shallow incisure, each lip asymmetrically rectangular with a smooth margin and one tine; three labial probolae, bifurcated at about 1/5 of their length; pharyngeal corpus 4.2–5.4 times isthmus length; nerve ring and excretory pore at level of isthmus and deirids at level of bulb; vulva and spermatheca undescribed, postuterine sac about 1 vulval body diameter long; spicules 21–25 µm long.
Material examined
NEW ZEALAND: 2 ♂♂, SMNH 135945–135946, 18 May 2008, North Island, Wanganui, Castlecliff beach, partly stabilized coastal sand dunes with Ammophila arenaria, 50 cm deep, legit G. Yeates.
Description
Adult
Body slightly arcuate ventrad when killed by heat. Cuticle annulated, annuli 2.4 µm wide at midbody and 3.0– 3.4 µm wide in pharyngeal region. Cuticle tessellated: longitudinal striae giving it a tiled appearance, tiles are not equal in size and are not arranged in straight rows, approximately 40–44 rows of blocks at midbody. Lateral field with five incisures occupying about 20% of body diameter, extending almost to tail terminus in females. Lip region slightly offset, carrying 6 + 4 papillae and two round amphids. Three pairs of asymmetrical lips, one dorsal and two ventrolateral. Pairs of lips separated by U-shaped primary axils without guarding processes. Each pair with a shallow incisure demarcating a secondary axil. Each lip asymmetrically rectangular with a smooth margin and one acute tine extending along the primary axil. Three labial probolae, 7.0– 8.5 µm high, bifurcated at about 1/5 of their length. Stoma somewhat longer than lip region diameter. Stomatal parts not clearly discernible. Cheilorhabdia bacilliform in lateromedian view; metastegostom with a dorsal denticle. Pharynx cephaloboid. Pharyngeal corpus cylindrical; isthmus narrow, not clearly demarcated from corpus; bulb oval, with valves. Nerve ring and excretory pore at level of isthmus and deirids at level of bulb.
Male
Reproductive system monorchic, dextral in position; testis reflexed ventrad anteriorly. Spicules paired and symmetrical, curved ventrad; with oval manubrium and subcylindrical, gradually narrowing shaft. Gubernaculum wedge-shaped, cornua crurum present. Tail strongly arcuate ventrad, conoid with rounded terminus. The two outer lateral lines extend posterior to the subdorsal papilla close to tail terminus, transforming into a cuticular ridge that reaches tail terminus. Genital papillae arranged as follows: two pairs subventral precloacal (at 36 µm and at 74 µm anterior to cloaca), one pair subventral adcloacal, a single midventral papilla on anterior cloacal lip; two pairs (one ventrosublateral and one lateral) at midtail; three pairs (one lateral, one subventral and one dorsosublateral) closer to tail terminus. Phasmids located at about two-fifths to half of tail length.
Female
Not found in our study.
Remarks
The specimens described here agree well in main morphological and morphometric features with the original description by Yeates (1967) of the males of S. tuarua from New Zealand.
Key to species
1. Lateral field with five incisures; cuticle with over 40 longitudinal rows of blocks; labial probolae biacute apically ............................................................................................... S. tuarua Yeates, 1967
– Lateral field with three-four incisures; cuticle with 12–26 longitudinal rows of blocks; labial probolae bifurcate half of length ...................................................................................................................... 2
2. Labial probolae with minute secondary bifurcations at tips ........................... S. iketaia Yeates, 1967 – Labial probolae without minute secondary bifurcations at tips ........................................................ 3
3. Cephalic probolae in shape of acute tines present on all six lips along the primary axils; cuticle with 24–26 longitudinal rows of blocks ................................... S. arenaria Boström & Holovachov, 2012
– Cephalic probolae absent, or present only on lateral lips along the primary axils; cuticle with 12–22 longitudinal rows of blocks ............................................................................................................... 4
4. Cuticle with 22 longitudinal rows of blocks ......................................... S. georgica Bagaturija, 1973 – Cuticle with 12–16 longitudinal rows of blocks ............................................................................... 5
5. Parthenogenetic species; spermatheca 7–13 µm long; postuterine sac about 7–17 µm long ............. ............................................................................................................ S. ophioglossa Andrássy, 1967 – Amphimictic species; spermatheca 24–43 µm long; postuterine sac about 22–36 µm long ............ 6
6. Cephalic probolae absent ............................................................................. S. incisa (Thorne, 1937) – Cephalic probolae setose, present on lateral lips only ................................ S. laterocornuta sp. nov.
description: Published as part of Boström, Sven & Holovachov, Oleksandr, 2014, Descriptions of species of Stegelleta Thorne, 1938 (Nematoda, Rhabditida, Cephalobidae) from California, New Zealand and Senegal, and a revision of the genus, pp. 1-19 in European Journal of Taxonomy 87 (87) on pages 3-17, DOI: 10.5852/ejt.2014.87, http://zenodo.org/record/3835107