Enchodelus, Thorne, 1939

Guerrero, Pablo, Liébanas, Gracia & Santiago, Reyes Peña-, 2008, Nematodes of the order Dorylaimida from Andalucía Oriental, Spain. The genus Enchodelus Thorne, 1939. 2. Description of three known species with rounded tail and long odontostyle, Nematology 10 (4), pp. 451-470 : 451-457

Enchodelus groenlandicus ( Ditlevsen, 1927) Thorne, 1939 = Dorylaimus (Doryllium) groenlandicus Ditlevsen, 1927 = Dorylaimellus groenlandicus ( Ditlevsen, 1927) Thorne & Swanger, 1936

( Figs 1-3 )

MATERIAL EXAMINED

Fourteen females collected from the provinces of Granada and Jaén .

MEASUREMENTS

See Table 1 DESCRIPTION

.

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Female

Moderately stout nematodes of medium size, 1.57-2.07 mm long. Habitus after fixation slightly curved ventrad, adopting an open C-shape. Body cylindrical, tapering towards both ends but more so towards anterior. Cuticle 3.0- 6.0 µ m in anterior region, 4.0-6.0 µ m at mid-body and 8.5-12.0 µ m on tail; its outer layer almost smooth or bearing very fine transverse striations, much thinner than inner one, especially at level of tail. Lateral chord relatively narrow, occupying 9-16% of mid-body diam., lacking any particular differentiation. Lateral pores visible along lateral chord. Lip region rounded in superficial view, moderately truncate when seen in optical section, varying from practically continuous to offset by a more or less (usually poorly) marked depression, 2.5-3.4 times as broad as high and ca one-third to two-fifths of body diam. at neck base. Lips amalgamated; labial and cephalic papillae barely perceptible. SEM photographs revealing oral aperture as a dorso-ventral slit, encircled by an oval projection of inner portion of lip region; perioral area showing strong radial striae; inner labial papillae located on distinct elevations, outer labial and cephalic papillae on less marked areas. Amphid fovea cup-shaped, opening at level of cephalic depression and occupying two- to three-fifths of corresponding body diam. Cheilostom cylindrical, with no particular differentiation. Odontostyle long, rather slen- der, with distinct walls and narrow lumen; 17-20 times as long as wide or 2.0-2.7 lip region diam. long; aperture small, occupying 6-11% of total length. Odontophore 0.9-1.2 times as long as odontostyle, with distinct basal flanges extending over posterior half of its total length and consisting of six sclerotised rods with small basal knobs. Guiding ring double, located at 27-37 µ m or 1.2- 1.7 lip region diam. from anterior end. Pharynx composed of a slender but well muscled anterior portion expanding gradually into basal expansion at 57-66% of total neck length, reaching full diam. at 63-72%; pharyngeal expansion occupying 31-39% of total neck length, ca two-fifths to two-thirds of corresponding body diam. Pharyngeal gland nuclei located as follows (n = 10): DN = 64-72; S 1 N 1 =?; S 1 N 2 =?; S 2 N 1 = 53-60; S 2 N 2 = 53-63. Weak membrane-like structure surrounding base of pharyngeal expansion. Cardia very small, rounded conoid, wider than long, 13-21 × 10-14 µ m. In some specimens, intestine containing greenish material. Genital system didelphic-amphidelphic, both branches equally and well developed. Ovaries relatively large, 108-243 µ m long, sometimes reaching sphincter level; oocytes first intwo or more rows, then in one row. Oviduct 95-273 µ m long, or 1.3-3.3 corresponding body diam., consisting of slender portion with prismatic cells and well developed pars dilatata with distinct lumen. Sphincter distinct, located between oviduct and uterus. Uterus long, 171-250 µ m or 2.1-3.1 corresponding body diam.; tripartite, i.e., consisting of wider proximal portion with distinct lumen followed by narrower intermediate long region with narrow lumen and surrounded by cluster of hyaline cells, and ending with well developed spheroid pars dilatata distalis. Four females bearing eggs: one with six, another with four, two with one egg each. Eggs measuring 72-100 × 33-51 µ m. Sperm not observed in genital tract. Vagina extending inwards 38-61% of body diam.; pars proximalis longer than broad, 20-33 × 15-23 µ m, with slightly curved walls, enveloped by a weak circular musculature; pars refringens with (in lateral view) two massive trapezoid sclerotisations with a combined width of 18-23 µ m; pars distalis 3.0-7.0 µ m long. Vulva a transverse slit, preceded byshallow depression in body surface; under SEM, vulva appearing surrounded by a spindle-shaped area clearly differentiated from adjacent body surface. Prerectum 3-6 and rectum 0.7-1.3 anal body diam. long. Tail rounded conoid to hemispheroid, with some very small saccate bodies on ventral side; terminal cuticle 8.5-13.0 µ mthick or 31-60% of total length. Two pairs of subterminal caudal pores, one subdorsal, another practically lateral.

Male

Unknown.

DIAGNOSIS AND RELATIONSHIPS

Andalusian material of E. groenlandicus is distinguished by its body length of 1.57-2.07 mm, lip region practically continuous and 19-22 µ m broad, odontostyle (44) 47-53 µ m long or 2.0-2.7 times lip region diam., odontophore provided with distinct basal flanges and practically as long as odontostyle, neck length 322- 401 µ m, pharyngeal expansion 111-142 µ m long or 31- 39% of total neck length, female genital system amphidelphic, uterus long and tripartite, pars refringens vaginae with two trapezoid sclerotisations, vulva a pre-equatorial (V = 42-49) transverse slit, tail rounded conoid to hemispheroid (22-37 µ m, c = 53-83, cļ = 0.6-0.8), and males unknown.

Because of its short, rounded conoid tail, long odontostyle and tripartite uterus, E. groenlandicus resembles E. macrodorus and E. saxifragae. It can be distinguished from both species by its longer odontostyle of 44 µ m long or more, but almost always around 50 µ m, vs 38-43 µ m in E. macrodorus and 37-47 µ m in E. saxifragae, although normally around 40 µ m. Additionally, it can be distinguished from E. macrodorus by a more differentiated and longer uterus (171-250 µ m or 2.1-3.1 times corresponding body diam. vs 61-143 µ m or 0.9-2.0 timesbody diam.) bearing a more developed pars dilatata distalis. It differs from E. saxifragae in the shape of the lip region (weakly offset by depression in E. groenlandicus vs distinctly offset by a constriction in E. saxifragae), shape of pars refringens vaginae in lateral view (trapezoid vs drop-shaped pieces), and absence of males.

DISTRIBUTION

This species was collected from four samples: five females from a wet meadow at 1950 m a.s.l. and three from a hedgehog heath at 2450 m a.s.l. in Sierra Nevada (province of Granada); two from a meadow at 955 m a.s.l. in Despeñaperros (province of Jaén); and four from an unknown locality of eastern Andalucía. It coexisted with E. macrodorus in one sample and with E. saxifragae in another one, both from Sierra Nevada.

IDENTITY OF THE IBERIAN MATERIAL

Ditlevsen’s (1927) original description of E. groenlandicus was based on only one female and lacks some important features so it is not possible to confirm absolutely the identity of our material. The main difference between the Iberian specimens and the female from Greenland is the body length (L = 1.57-2.07 vs 2.5 mm). They also differ in the relative length of the neck (b = 4.6-5.5 vs 6) and tail (c = 53-83 vs 50). In this respect, it seems that Ditlevsen made a mistake in the measurement of the tail, which should have a length of 50 µ m according to the length of the body and c index. However, Ditlevsen’s Figure 12 shows a tail with a length of ca 31 µ m, which would imply a c index of 81. These last figures are in better agreement with the measurements of the Iberian specimens (tail length 22-37 µ m, c = 53-83). In addition, the material studied fits quite well the original description and the fact that this is the only Enchodelus species having a rounded tail and odontostyle ca 50 µ m long leads us to attribute our material to the species from Greenland with a high degree of confidence. Assuming this to be correct, the distribution of this species indicates a disjunct geographical distribution. As they occur mostly at high elevations in the southern Iberian Peninsula, such a distribution pattern might stem from quaternary glacial events.

REMARKS

Enchodelus groenlandicus was reported on a cotton field in Uzbekistan (Khakimov, 1973 in Tulaganov and Usmanova, 1978). However, the Asiatic material certainly belongs to a different species, due to the extremely short body (L = 0.72 mm) and postequatorial vulva (V = 61.9).

Figures

Fig. 1. Enchodelus groenlandicus (Ditlevsen, 1927) Thorne, 1939 (female). A: Entire body; B: Neck; C: Anterior region; D: Reconstruction of superficial appearance of anterior region, lateral view; E: Anterior genital branch; F: Tail; G: Vulval region. (Scale bars: A = 500 µm; B, E = 100 µm; C, D, F, G = 50 µm.)

Fig. 2. Enchodelus groenlandicus (Ditlevsen, 1927) Thorne, 1939 (female). A: Variability of anterior region; B: Neck showing location of dorsal gland nucleus (large arrow) and one of subventral gland nuclei (small arrow); C: Anterior genital branch, with location of sphincter between uterus and oviduct marked by arrow; D: Detail of uterus-oviduct junction showing sphincter, distal pars dilatata uteri and cluster of hyaline cells surrounding intermediate narrow region of uterus; E: Entire body of female with four eggs; F: Variability of vulval region; G: Variability of tail. (Scale bars: A, D, F, G = 20 µm; B, C = 100 µm; E = 200 µm.)

Fig. 3. SEM micrographs. A-C: Enchodelus groenlandicus (Ditlevsen, 1927) Thorne, 1939, anterior end. A: Semi en face view; B: Lateral view; C: En face view. D-F: Enchodelus macrodorus (de Man, 1880) Thorne, 1939, anterior end. D: Semi en face view; E: Lateral view; F: En face view. G-I: Enchodelus saxifragae Popovici, 1995, anterior end. G: Semi en face view; H: Lateral view; I: En face view. J-L: Vulval region, J: Enchodelus groenlandicus; K: Enchodelus macrodorus; L: Enchodelus saxifragae. (Scale bars: A, B, E, G, H, J-L = 20 µm; C, D, F, I = 10 µm.)