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 : 457-462

Enchodelus macrodorus (de Man, 1880) Thorne, 1939 = Dorylaimus macrodorus de Man, 1880 = Dorylaimus (Doryllium) macrodorus (de Man, 1880) Ditlevsen, 1928 = Dorylaimellus macrodorus (de Man, 1880) Thorne & Swanger, 1936

( Figs 3 , 4 )

MATERIAL EXAMINED

Eleven females from Sierra Nevada (province of Granada).

MEASUREMENTS

See Table 2 .

SEM OBSERVATIONS

Lip region considerably elevated. Oral aperture appearing as a dorso-ventral rhomboidal slit. Perioral region slightly elevated, with very subtle radial striae. Labial and cephalic papillae located on rather small elevations of lip region surface, comparatively less marked than in E. groenlandicus and E. saxifragae; circular striae surrounding inner labial papillae, forming a ring-like structure; but outer labial and cephalic papillae located on less differentiated areas. One lateral pore observed at base of amphid fovea. Vulva an oval transverse aperture preceded by a slight depression in body contour.

DISTRIBUTION

The species was collected in three samples in Sierra Nevada (province of Granada); two of them in wet meadows at 2925 and 1950 m a.s.l., and one from river bank soil around poplar at 1400 m a.s.l. It co-occurred with E. groenlandicus in one sample.

REMARKS

Iberian individuals are practically identical to American material collected by Thorne during the years 1924-1932 and redescribed by Guerrero and Peña-Santiago (2007), except for minor differences in morphometry such as the broadening of body length range (1.38-1.92 vs 1.49-1.70 mm) and, consequently, the de Man indexes; slightly more posterior vulva (V = 42-46 vs 41-44); shorter uterus (56- 115 µ m long or 0.9-1.6 times corresponding body diam. vs 61-143 µ m long or 1.1-2.0 timesbody diam.); shorter prerectum (112-176 vs 162-212 µ m); and longer tail (22- 28 vs 18-24 µ m). These differences can be explained by the scarcity of available material (eight American and ten Spanish individuals).

THE IDENTITYOF ENCHODELUS MACRODORUS

In spite of being the type species of the genus, identification of E. macrodorus is rather problematical. The original description by de Man (1880) was useful at the time to distinguish between a generalised Enchodelus species with rounded tail and the vast number of dorylaim species which were then classified within the genus Dorylaimus (including representatives of Dorylaimidae , Aporcelaimidae , Qudsianematidae , Nordiidae or even Nygolaimidae ). No illustrations were provided in 1880, but they were included in a subsequent work (de Man, 1884). Unfortunately, it seems that de Man’s slides containing individuals of E. macrodorus were lost before Loof (1961) revised the nematode collection of de Man, since this species is not redescribed in that work.

This has been the most cited Enchodelus species, reported from all of the Holarctic region, from the USA (Thorne, 1939) to Korea (Choi et al., 1997). However, the ambiguity of its diagnosis probably led to misidentifications and some of the records may correspond to other species. Asummary of E. macrodorus records, including morphometric data, is presented in Table 3 . Some remarks follow below.

Previous records considered to represent the true E. macrodorus

Taking into account that holotype and paratypes were so briefly described and that they are probably lost, the diagnosis of the species must be inferred from other sources. The only reports from the original country of description, i.e., The Netherlands, are those by de Man (1880, 1884 and 1912, the latter cited by Menzel, 1914) and Bongers (1988), so they are considered to correspond with the true E. macrodorus. In a recent work, two of the authors of the present paper had the opportunity to redescribe American individuals of Enchodelus species collected by Thorne (Guerrero & Peña-Santiago, 2007), and, among them, eight females originally identified as E. macrodorus, which apparently fit well with specimens from The Netherlands. From this starting point, the most relevant characters for E. macrodorus are body length of ca 1.5-1.8 mm, odontostyle ca 40 µ m long, and a particularly anterior located vulva (V = ca 40-44).

The following records agree well with this short diagnosis and can be considered to be conspecific with E. macrodorus: allpopulations reported by Thorne (1939), Jairajpuri and Loof (1968), Ahmad and Jairajpuri (1980), Nasira et al. (1992), and Ahmad et al. (2002). In addition, three of the populations reported by Popovici (1995), specifically those composed of nine and five females, and that by four females measuring 1.55-1.73 mm offer no reason to reject this attribution.

Previous records which probably do not correspond to E. macrodorus

Menzel (1914): body too short in females (L = 1-1.2 mm) and excessively variable in males (L = 1.3-2.16 mm). May correspond to more than one species.

Schneider (1923): vulva located not especially anterior (V = 45.5-48.5).

Kreis (1924): body exceedingly short (L = 0.82-1.01 mm).

Stefański (1924): odontostyle and total stylet length too short (total stylet length is reported to be 69-70 µ m. Since odontophore is normally as long as or longer than odontostyle, the latter will barely reach 35 µ m long).

Andrássy (1952): body length somewhat short (L = 1.15-1.36 mm in females, 1.42 mm in males); vulva located not particularly anterior (V = 44-50); and odontostyle exceedingly short (20-29 µ m in females, 24-35 µ m in males).

Van Rossen and Loof (1961): vulva located not particularly anterior (V = 47-51).

Nesterov (1979): vulva not always located particularly anterior (V = 43-50), odontostyle too long (52 µ m as estimated from original illustration), lip region expanded and rather broad (27 µ m as calculated from drawing).

Vinciguerra (1984): body too short (L = 0.90-1.32 mm in females and 0.94-1.22 mm in males); vulva located practically equatorial (V = 45-52); and odontostyle exceedingly short (27-37 µ m).

Popovici (1995 in part): all populations with odontostyle shorter than 36 µ m, including all described males. Some of the females have, in addition, the body rather short and vulva located quite posterior.

Choi et al. (1997): vulva located practically equatorial (V = 48-55); odontostyle somewhat short (35-40 µ m).

Previous records doubtful or with insufficient data to assess identity

Tulaganov (1958, cited in Tulaganov and Usmanova, 1978): vulva located only slightly pre-equatorial (V = 46- 49); and odontostyle rather too long (40-50 µ m).

Loof (1971): odontostyle length seems to be somewhat long (48 µ m, but compare with odontostyle length 42-47 µ m in individuals from China described by Ahmad et al., 2002). Remaining measurements fit well with diagnosis of E. macrodorus.

Winiszewska-Slipinska (1987): odontostyle length somewhat long (46 µ m, see above) and c index apparently too low (c = 42-52 vs 70-80 in original description, which leads to a rather long tail, i.e., 36 µ m as estimated from L and c index vs 24 µ m as estimated from the original description and 18-24 µ m in American individuals reported by Guerrero and Peña-Santiago (2007).

Identityof populations describedby Brakenhoff (1914), Stefański (1927), Ditlevsen (1928), Allgén (1953), Altherr (1953), Zullini (1970) and Thorne (1974) cannot be confirmed due to lack of information.

As a curiosity, Coomans (1985) beautifully illustrated the anterior region of E. macrodorus in his study on longidorid phylogeny. The specimens used for the drawings were provided by Loof, but nothing is said about their origin and no morphometric data are available.

EMENDED DIAGNOSIS OF E. MACRODORUS

Taking into account all the information collected from the most reliable bibliography, the redescription of the species on the basis of American individuals by Guerrero and Peña-Santiago (2007), and observations on Iberian specimens, the following emended diagnosis for the species is provided: body 1.38-1.92 mm long, lip region offset by more or less marked depression and 15-20 µ m diam., odontostyle 37-44 µ m long or 1.7-2.5 times lip diam. and rarely somewhat shorter or longer (ranging from 33-48 µ m), odontophore with distinct basal flanges consisting of six sclerotised pieces and 1.0-1.5 times longer than odontostyle, total length of stylet 78-100 µ m, neck length 288-400 µ m, pharyngeal expansion 110- 145 µ m and occupying 35-40% of total neck length, female genital system amphidelphic, uterus rather short, tripartite but with poor development of each region, 0.9-2.0 times body diam. long, pars refringens vaginae formed by two trapezoidal sclerotisations, vulva a transverse slit and uniquely anterior (V = 37-47), tail short, rounded to hemispherical (18-30 µ m long, c = 55-91, cļ = 0.5-0.7 in females, and 18-22 µ m long, c = 67-100, cļ = 0.6 in males), males very rare, bearing 6-12 spaced ventromedian supplements with posterior one in range of the spicules.

Figures

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.)

Fig. 4. Enchodelus macrodorus (de Man, 1880) Thorne, 1939 (female). A: Variability of anterior region; B: Neck showing dorsal gland nucleus (large arrow) and one of subventral gland nuclei (small arrow); C: Anterior genital branch showing sphincter between uterus and oviduct (arrow); D: Detail of uterus-oviduct junction, displaying sphincter (arrow) and weak development of uterus; E: Vulval region; F; Entire body; G: Variability of tail. (Scale bars: A, D, E, G = 20 µm; B = 100 µm; C = 50 µm; F = 250 µm.)