Enchodelus groenlandicus (Ditlevsen, 1927) Thorne, 1939

Elshishka, Milka, Lazarova, Stela & Peneva, Vlada K., 2012, Studies of the genus Enchodelus Thorne, 1939 (Nematoda, Nordiidae) from Arctic polar deserts. 1. Species with long odontostyle: E. makarovae sp. n. and E. groenlandicus (Ditlevsen, 1927) Thorne, 1939, with an identification key to the species of the E. macrodorus group, ZooKeys 212, pp. 1-23 : 6-9

Enchodelus groenlandicus (Ditlevsen, 1927) Thorne, 1939

Figs 7 11

Material examined.

Ten females collected from Putorana Plateau, Russian Arctic ( Table 1 ).

Measurements.

See Table 4 .

Description.

Female. Nematodes of medium to large size, habitus from slightly curved ventrad to open C- shape after fixation. Cuticle with fine, but distinct transverse striations, especially visible at neck and on tail regions; 4-6 µm thick at postlabial region, 3-4 µm at mid-body and 7-8 µm on tail. Lateral chord narrow, 6-9 µm wide or occupying ca 9-13 % of mid body diam. Lip region rounded, offset by a depression, 2.3-3.1 times as wide as high. Amphidial fovea cup-shaped, located at level of labial depression, occupying 65% of lip diam. Cheilostom cylindrical. Odontostyle long, 2-2.5 times longer than lip region diam. or 2.2-2.7% of total body length. Odontophore distinctly flanged, 1.1-1.3 times as long as odontostyle. Guiding ring double, located 1.4-1.6 lip region diam. from anterior end. Pharynx attains full width at 56-64% of its length from anterior end. Pharyngeal characters are presented at Table 3. Cardia rounded measuring 6-10 × 15-17 µm. Genital system amphidelphic, both branches equally and well developed, anterior 277-370 µm, posterior 287-375 µm long. Ovaries relatively large, 142-303 µm long; oocytes firstly in two or more rows, then in a single row. Anterior and posterior oviduct 119-143 µm (n=9) and 119-153 µm (n=8) long, 1.6-1.9 and 1.6-2.0 times body diam. respectively, consisting of slender part and well developed pars dilatata oviductus. Sphincter distinct. Uterus thick walled, tripartite, consisting of a wider proximal portion with distinct lumen, followed by a narrower median portion (43-115 µm (n=4)) and ending with a well developed spheroid pars dilatata distalis. Vagina extending inwards 42-53 μ m or 53-68 % of body diam., pars proximalis 25-30 µm × 21-22 µm, pars refringens with two trapezoid sclerotisations, with a combined width of 18-18.5μm and length 6-8 μm (n=2) pars distalis 6 µm long (n=2). Vulva a transverse slit, pre-equatorial (40-47%). Eggs observed in eight females, measuring 96 -109 × 43-64 µm, most frequently located in pars dilatata oviductus (n=6), rarely in uterus (n=2). Prerectum 3-4.5 anal diam. long, rectum 0.8-1.0 times anal body width. Tail hemispheroid. Numerous small elongated saccate bodies observed on tail, mostly on ventral side. Hyaline part of tail 8.0-10 µm thick or 25-33 % of total tail length.

Male. Unknown

Locality and plant associations.

Different types of vegetation from a polygonal polar desert on Plateau Putorana, Russian Arctic ( Table 1 ).

Remarks.

The data on Enchodelus groenlandicus geographical distribution, i.e. the original description from Disko Island, Greenland ( Ditlevsen 1927) and recent reports from Spain, Albania and Iran ( Guerrero et al. 2008, Andrássy 2009b, Pedram et al. 2011) indicate a disjunctive type of range. It occurs at high altitudes 950 m to 2450 m a.s.l in Southern Europe and Iran, and at high latitudes in the polar region (Putorana Plateau and Greenland), Guerrero et al. (2008) hypothesize that such a distribution pattern might stem from quaternary glacial events. The specimens examined generally agree well with data reported for this species, although some differences occurred: the Arctic population has somewhat shorter odontostyles (43-47 vs 44-53 µm) and a more anterior position of the vulva (40-46 vs 41.5-49.4%, see Table. 4 for details); Iranian specimens had shorter female tails (19-24 vs 28-33 μ m and c’ = 0.4-0.6 vs 0.5-0.7). We consider the morphometric differences as representing intraspecific variation.

Identification key to species belonging to Enchodelus macrodorus group

1	Odontostyle ≤ 36 µm; uterus bipartite (♀ L=1.85 mm, a=20, b=5.1, c=58, c’ =0.76, V=53%, Odontostyle=36 μm; ♂ unknown) (India)	Enchodelus distinctus (Ahmad & Jairajpuri, 1980)
-	Odontostyle ≥37 µm; uterus tripartite	2
2	Lip region separated by constriction	3
-	Lip region separated by depression	4
3	Body long (>1.6 mm) (♀ L=1.8-2.38 mm, a=21-34, b=4.8-6.1, c=54-92, c’ =0.6-0.9, V=44-50%, Odontostyle=38-45 µm; ♂ L=1.66-2.21mm a=24.4-32.7, b=5.1-5.9, c=53.2-68, c’ =0.7-0.8, Odontostyle=27.5-40 µm, Spicules= 56-70 µm) (Romania, Spain)	Enchodelus saxifragae (Popovici, 1995)
-	Body short (<1.6 mm) (♀ L=1.21-1.56 mm, a=20-25.5, b=3.0-5.0, c=60.5-92.5, c’ =0.5-0.7, V=44-49%, Odontostyle=40-45 μm; ♂ L=1.31-1.53 mm, a=22.5-28, b=4.3-5.1, c=49-71.5, c’ =0.5-0.9, Odontostyle=39-44 μm, Spicules=49-61 μm) (Iran)	Enchodelus babakicus (Pedram et al., 2009)
4	Uterus short (1-2 times corresponding body diam.) (♀ L=1.38-1.92 mm, a=19-32, b=4.0-6.2, c=55-91, c’ =0.5-0.7, V=37-47%, Odontostyle=37-44 μm; ♂L=0.94-2.16 mm, a=19-39, b=3.6-6.0, c=41-100, c’ =0.6-0.9, Odontostyle=24-33 µm, Spicules=46-70 µm) (Holarctic region)	Enchodelus macrodorus (de Man, 1880) Thorne, 1939)
-	Uterus long(> 2 times corresponding body diam.)	5
5	Body length <1.3 mm; (♀ L=0.94-1.29 mm, a=19-28, b=3.5-5.6, c=47-73, c’ =0.5-1.0, V=43-55%, Odontostyle=37-45 μm; ♂ L=1.24-1.28 mm, a=26-37, b=4.6-4.8, c=52-54, c’ =0.7-0.8, Odontostyle=38-40 μm, Spicules = 45-50 μm) (India, Korea)	Enchodelus microdoroides (Baqri & Jairajpuri, 1974)
-	Body length>1.5 mm	6
6	Dorsal cell mass near cardia present. (♀ L=1.59-1.87 mm, a=21.1-28.6, b=4.3-5.3, c=55.3-87.5, c’ =0.5-0.7, V=41.7-49.7%, Odontostyle=39.5-47 μm) (Romania)	Enchodelus carpaticus (Ciobanu et al., 2010)
-	Dorsal cell mass near cardia absent	7
7	Lip region narrow <18 µm, males present (♀ L=1.57-2 mm, a=21.6-33.1, b=4.4-5.7, c=45.8-70.3, c’ =0.6-0.9, V=45-51%, Odontostyle=38-43 µm; ♂ L=1.49-1.79 mm, a=19.6-29.8, b=4.4-5.4, c=46.4-58.9, c’ =0.7-0.8, Odontostyle=39-44.5 µm, Spicules=65-74 μm) (Russia - Severnaya Zemlya Archipelago)	Enchodelus makarovae sp. n.
-	Lip region wide,> 19 μm, males absent (♀ L=1.54-2.5 mm, a=20.3-25.9, b=4.0-6.0, c=40-104, c’ =0.4-0.8, V=40-49%, Odontostyle=43-51 μm) (Greenland, Spain, Albania, Iran, Russia - Putorana Plateau)	Enchodelus groenlandicus (Ditlevsen, 1927)

Figures

Figure 7. Enchodelus groenlandicus. A-D Female A Neck region B Anterior genital branch C, D Entire body. Scale bars: A, B 50 µm; C, D 500 µm.

Figure 11. Enchodelus groenlandicus. A-E Female: A Pharyngeal bulb B Pars dilatata distalis uteri (arrows) C Vulval region in subventral view D, E Vulval region in lateral view. Scale bars: A-E 50 µm.