Enchodelus enguriensis Elshishka, Mladenov, Altash, Tskitishvili, Álvarez-Ortega, Peña-Santiago & Peneva, 2024

Elshishka, Milka, Mladenov, Aleksandar, Altash, Stela, Álvarez-Ortega, Sergio, Peña-Santiago, Reyes & Peneva, Vlada, 2024, Cyber catalogue and revision of the nematode genus Enchodelus (Dorylaimida, Nordiidae), Biodiversity Data Journal 12, pp. e 126315-e 126315 : e126315-

Enchodelus enguriensis Elshishka, Mladenov, Altash, Tskitishvili, Álvarez-Ortega, Peña-Santiago & Peneva sp. nov.

Description

Material examined. Four females, five males and twelve juveniles (J 1 - J 4) from Georgia.

Measurements (see Table 1 )

Adult (Figs 11 , 12 , 13 , 14 , 15 ). Moderately slender (a = 20-27) nematodes of medium size, 1.03-1.40 mm long. Body cylindrical, tapering towards the ends. Upon fixation, habitus regularly curved ventrad, C-shaped. Cuticle two-layered, 3-3.5 µm thick at level of the guiding ring, 2.5 µm at mid-body and 6-8 µm on tail, layers with different refraction, the outer one visibly thinner than the inner one and bearing very fine transverse striation, inner layer with slight radial striation, especially visible at tail. Lateral chord very narrow, with granular aspect and lacking any differentiation. Several dorsal and ventral body pores are present at cervical region. Lip region rounded, offset from the adjoining body by a weak, but distinct depression, 2.7-3.6 times as wide as high, with mostly amalgamated lips and distinct papillae visibly protruding above the lip region contour. Amphidial fovea funnel-like, its aperture more than half of lip region diameter. Cheilostom a truncate cone to almost cylindrical, thick-walled. Odontostyle long and slender, straight, 2.1-2.5 times the lip region diameter, 18-20 times as long as wide and 2.6-3.7 % of body length, with very narrow lumen and minute aperture occupying hardly 5 % of its length. Guiding ring double, located at 1.3-1.7 times lip region diameter from anterior end. Odontophore 1.1-1.2 times as long as odontostyle, thickened, bearing flange-like extensions at its base. Pharynx entirely muscular, gradually enlarging into the basal expansion 87-94 µm long that occupies one-third of the total neck length, pharyngeal gland nuclei and their orifices located as follows: DO = 69-70 %, DN = 71-74 %, SN = 87-89 %, PS 1 = 41-48 %, PS 2 = 40-46 %. Nerve ring located at 160 μm from the anterior end. Pharyngo-intestinal junction consisting of a short and rounded cardia and a weak ring-like structure surrounding pharyngeal base.

Female. Genital system diovarian, with both branches equally developed, the anterior 250 µm long, the posterior 240 µm (n = 1). Ovaries relatively short, often not reaching the sphincter level. Oviduct with well-developed pars dilatata bearing distinct lumen. Sphincter between oviduct and uterus well developed. Uterus long, 126-152 μm or 2.5-2.8 times the corresponding body diameter, tripartite, consisting of a wider proximal portion, a longer and much more slender intermediate section with a narrow lumen and surrounded by cluster of hyaline cells and a well-developed, spheroid, distal pars dilatata. Vagina extending inwards to 57-59 % of body diameter: pars proximalis 19-20 x 18.5-19 μm, pars refringens with (in lateral view) two rectangular sclerotised pieces whose combined width is 14-17 μm, pars distalis 3-5 μm long. Vulva a transverse slit. Prerectum 3.0-4.1, rectum 0.9-1.1 times anal body diameter length. Tail convex conoid, 1.5-1.9 % of body length, with bubble – like or saccate bodies mostly on ventral side, inner core occupying 50-70 % of tail length, caudal pores two pairs.

Male. General morphology similar to that of female. Genital system diorchic, with opposite testes. Sperm cells spindle-shaped, 8-9 x 2 μm. In addition to the ad-cloacal pair, located at 7-9 μm from the cloacal aperture, there is a series of 9-10 spaced ventromedian supplements, one or two within the range of spicules, thus without hiatus. Spicules dorylaimoid, 1.4–1.9 times the body diameter at level of the cloacal aperture, 4-5 times as long as wide its maximum width: head occupying 20-25 % of total length, ventral side bearing prominent hump and hollow, posterior end 6-7 μm wide. Lateral guiding pieces cylindrical with asymmetrical bifurcate end (Figs 12 , 15 ), reaching the spicule terminal tip, measuring 13-15 × 2-3 μm. Tail convex conoid, with two pairs of caudal pores.

Juveniles (Figs 16 , 17 ). Based on morphometric of juvenile specimens and the relationships between the lengths of their functional and replacement odontostyles and body lengths, four juvenile stages were identified. Habitus in first juvenile stage almost straight, lip region flat, continuous with the body, genital primordium 8 μm long, tail ventrally curved with long central peg, 20 μm long.

Tail in J 2 and J 3 conoid elongated in J 4 bluntly conoid as in females, c’ decreasing during the successive stages to J 4 and females.

Molecular characterisation

One D 2 - D 3 of 28 S rRNA gene sequences was obtained for this species. In the D 2 - D 3 of 28 S rRNA (Fig. 4 ) gene tree, this sequence formed a highly-supported clade ( PP = 100) with E. macrodorus and other three Enchodelus sequences from GenBank.

Diagnosis

Enchodelus enguriensis sp. nov. is characterised by its 1.03-1.40 mm long body, lip region 16-17 μm wide and offset by weak depression, odontostyle 37–40 μm long or 2.1-2.5 times lip region diameter, odontophore flanged and 1.1–1.2 times as long as odontostyle, neck 270-290 μm long, pharyngeal expansion occupying one-third of the total neck length, female genital system diovarian, uterus tripartite, pars refringens vaginae with two rectangular sclerotisations, vulva ( V = 49–53 %), tail convex conoid (19-26 μm, c = 51-69, c’ = 0.5–0.8) bearing abundant saccate bodies; males abundant, spicules 54–61 μm long and 9-10 spaced ventromedian supplements without hiatus.

Relationships

Based on tail morphology and odontostyle length, this species can be assigned to the E. macrodorus – group as defined by Guerrero et al. (2008 b). This group includes E. babakicus , E. carpaticus , E. distinctus , E. groenlandicus , E. macrodorus , E. makarovae , E. microdoroides and E. saxifragae . This homogeneous group is characterised by the presence of a rather long odontostyle (> 35 μm), odontophore with well-developed flanges, uterus tripartite (except for E. distinctus , which has been described with a bipartite uterus ( Ahmad and Jairajpuri 1980) and hemispheroid to rounded conoid tail.

In having a lip region offset by a depression, the new species is most similar to E. carpaticus , E. groenlandicus , E. macrodorus , E. makarovae and E. microdoroides . The new species differs from:

Enchodelus carpaticus by its by slightly shorter odontostyle (37-40 vs. 39.5–47 μm), shorter neck length (280-290 vs. 336-388 μm) and pharyngeal expansion (87-94 vs. 136–167 μm), absence of dorsal cell mass near cardia vs. presence, shorter prerectum (90-124 vs. 164–272 mm) and tail (av. 20.5 (19–24) vs. av. 23.7 (21–29) μm), saccate bodies present vs. absent, males present vs. absent (males not found, but sperm cells were observed in one female) ( Ciobanu et al. 2010 a);

Enchodelus groenlandicus by its shorter body (L = 1.03-1.4 vs. 1.54–2.5 mm) and odontostyle (37–40 vs. 43–53 μm), somewhat more anteriorly located guiding ring (24-26.5 vs. 27–37 μm), narrower lip region (16–16.5 vs. 19–22 μm), more posterior vulva position ( V = 49-53 vs. 40-49 %), males present vs. absent ( Ditlevsen 1927, Andrássy 2009 a, Elshishka et al. 2012). A record from Iran ( Pedram et al. 2011) largely deviates from the morphometrics of other data for E. groenlandicus (e. g. lip region width, tail length) and is not included in the comparison.

Enchodelus macrodorus in having a shorter body (L = 1.03-1.4 vs. 1.38-1.92 mm) and pharyngeal expansion (87-94 vs. 110-145 μm), more posterior vulva position ( V = 49-53 vs. 37-47 %), a longer and more differentiated uterus (2.5-2.8 times longer than body diameter with long intermediate portion and well developed pars distalis vs. 0.9-2.0 times body diam. with very short intermediate region and poorly developed pars distalis), tail differently shaped (convex conoid vs. rounded to hemispherical), males abundant vs. males rare ( Guerrero et al. 2008 b).

Enchodelus makarovae by its shorter body (L = 1.03-1.4 vs. 1.57–2.00 mm), shorter odontophore (1.1-1.2 vs. 1.2–1.4 times as long as odontostyle), shorter neck length and pharyngeal expansion (280-290 vs. 320–377 μm and 87-94 vs. 113–130 μm long, respectively) and uterus (126-152 vs. 220-346 μm), males with shorter spicules (54-61 vs. 65–74 μm long), lateral piece shape (asymmetrically vs. symmetrically bifurcated) ( Elshishka et al. 2012);

Enchodelus microdoroides by having a wider lip region (16–16.5 vs. 13–14 μm), relatively shorter odontostyle (2.3-2.5 vs. 3 times lip region diameter), guiding ring located more anteriorly (24-26.5 vs. 28–39 μm from anterior end), differently-shaped pars refringens vaginae (rectangular vs. quadrangular), males abundant vs. males rare, longer spicules (54-61 vs. 45–50 μm) ( Baqri and Jairajpuri 1974, Ahmad and Jairajpuri 1980, Brzeski 1992).

The new species can be distinguished from the remaining three species of E. macrodorus group by its lip differentiation: lip region set off by depression vs. set off by a deep constriction. Further, it differs from:

Enchodelus babakicus by having cuticle smooth vs. striated, a slightly shorter and thinner odontostyle (37-40 vs. 40-45 μm and 18-20 vs. 13.6-15.3 times as long as wide, respectively), guiding ring located slightly more anterior (24-26.5 vs. 25-30 μm from anterior end), more posteriorly located vulva ( V = 49-53 vs. 44-49 %), differently-shaped pars refringens vaginae (rectangular vs. trapezoidal), thinner hyaline part of tail (29-47 vs. 42-57 % of tail length), differently-shaped lateral piece (asymmetrically vs. symmetrically bilobed) ( Pedram et al. 2011).

Enchodelus distinctus in having a shorter body length (L = 1.03-1.4 vs. 1.85 mm), longer odontostyle (37–40 vs. 36 μm), more posteriorly located guiding ring (1.5-1.7 vs. 1.4 times lip region diameter), pharyngo-intestinal disc present vs. absent, different structure of uterus (tripartite vs. bipartite), shorter tail (19-24 vs. 32 μm, c’ = 0.6-0.7 vs. c’ = 0.8), saccate bodies present vs. absent, males present vs. absent ( Ahmad and Jairajpuri 1980).

Enchodelus saxifragae by its shorter body length (L = 1.03-1.4 vs. 1.61-2.38 mm), a narrower lip region (16-16.5 vs. 18–22 μm), shorter neck length and pharyngeal expansion (280-290 vs. 319-490 μm and 87-94 vs. 116–186 μm long, respectively), shorter prerectum (90-124 vs. 140–294 μm) and fewer ventromedian supplements (9-10 vs. 13–16 in number) ( Popovici 1995 a, Guerrero et al. 2008 b, Ciobanu et al. 2010 a).

Type-locality and habitat

Georgia, Samegrelo-Zemo Svaneti Region, Bogreshi, Enguri River , Tower of Love , moss Tortella squarrosa (Brid.) Limpr. , geographical co-ordinates: 43 ° 00 ’ 01 N 42 ° 50 ’ 04 ” E, 1544 m a. s. l.

Type material

The holotype female, three paratype males and four paratype juveniles are deposited in the Nematode Collection of Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Bulgaria, under the accession numbers IBER-BAS NTC 107 -109 . Other paratypes are deposited as follows: one female, one male and three juveniles (accession numbers ISUZI 0010581, ISUZI 0010582) – in the Nematode Collection of the Department of Nematology, Institute of Zoology, Ilia State University, Tbilisi, Georgia; one female, one male and three juveniles (accession numbers 0714, 0715) – in the Nematode Collections of the Universidad de Jaén, Jaén, Spain; one female, two males and one juvenile (accession numbers T- 8075 p, T- 8076 p) – in the USDA Nematode Collection, Beltsville, Maryland, USA.

Etymology

The species is named after the River Enguri; it was recovered from the stone next to the Tower of Love on the bank of the river.

Distribution

Georgia

Notes

Morphometric data of all species (28) of genus Enchodelus are provided in Suppl. material 1.

Figures

Figure 4. Bayesian 50 % majority rule consensus tree as inferred from the D 2 - D 3 expansion segments of 28 S rRNA gene sequence alignment under the GTR + I + G model. Posterior probability values more than 70 % are given on appropriate clades. New sequences are indicated by bold letters.

Figure 11. Enchodelus enguriensis sp. nov., female (Holotype). A Anterior region; B Pharyngeal expansion; C Anterior genital branch; D Vulval region; E Tail end. Scale bar: A-E 25 µm.

Figure 12. Enchodelus enguriensis sp. nov., male. A Lip region; B Pharyngeal expansion; C, D Posterior end; E Spicules; F Sperm cells; G Lateral pieces. Scale bars: A-D 25 µm, E-G 25 µm.

Figure 13. Enchodelus enguriensis sp. nov., female. A, B Lip region; C Amphid; D Entire body; E Pars dilatata distalis uteri; F Lateral field. Scale bars: A-C, E, F 30 µm D 400 µm.

Figure 14. Enchodelus enguriensis sp. nov., female. A, B Vulval region; C, D Tails; E Saccate bodies. Scale bar: A-E 30 µm.

Figure 15. Enchodelus enguriensis sp. nov., male. A Lip region; B Amphid; C Pharyngeal expansion, dorsal gland; D Entire body; E Tail end and spicules; F Posterior end; G Lateral piece; H Sperm cells in testis. Scale bars: A-C, E, G, H 30 µm; D 400 µm; F 100 µm.

Figure 16. Enchodelus enguriensis sp. nov. juveniles. A-D Anterior region (A J 1, B J 2, C J 3, D J 4); E-H Tail ends (E J 1, F J 2, G J 3, H J 4). Scale bar: A-H 25 µm.

Figure 17. Enchodelus enguriensis sp. nov., juveniles. A-D Anterior region (A J 1, B J 2, C J 3, D J 4); E-H Tail ends (E J 1, F J 2, G J 3, H J 4). Scale bar: A-H 30 µm.