Amplimerlinius uramanatiensis, Ghaderi, Reza & Karegar, Akbar, 2014

Ghaderi, Reza & Karegar, Akbar, 2014, Description of Amplimerlinius uramanatiensis sp. n. (Nematoda: Merliniidae) and observations on three other species of the genus from Iran, Zootaxa 3869 (1), pp. 17-32 : 18-30

Amplimerlinius uramanatiensis sp. n.

( Figs 1 , 5 , 6 A, E, I)

Measurements. See Table 1.

Female. Body straight to C-shaped. Cuticle prominently annulated; annuli about 1.5–1.7 µm wide at mid-body. Lateral fields 11–14 µm wide or 29–34% of body width; sometimes irregularly areolated in pharyngeal and tail regions. Head conoid, usually with apex flattened or somewhat rounded, continuous with body contour, 4.0–5.2 µm high and 9.5–10.8 µm wide at base; perioral disc indistinct. Head with seven or eight annuli up to the end of outer extension of cephalic framework. Framework moderately sclerotized, outer margins extending over three body annuli. Anterior and posterior cephalids 8–10 and 19–21 µm respectively from the anterior end. Stylet welldeveloped, 2.8–3.1 times as the lip region width; conus 13.2–14.7 µm, slightly shorter than the shaft (m = 44–48); knobs 6.0–6.8 µm across, anterior surfaces slightly sloping backward. Orifice of dorsal pharyngeal gland 2.6–3.6 µm from the base of stylet. Deirids at level of hemizonid, two to four annuli anterior to the level of secretoryexcretory pore, lateral fields with six lines at this level. Hemizonid two to three annuli long, one to four annuli anterior to the secretory-excretory pore. Median pharyngeal bulb oval, with prominent valve plates, 20–22 x 14 –16 µm; distance from the anterior end to center of median bulb 93.6 (90.0–96.6) µm. Isthmus slender, 1.0–1.1 times as the length of the basal bulb. Nerve ring 116–121 µm from the anterior end. Basal pharyngeal bulb cylindrical, length/width ratio 2.1–2.7, offset from intestine; cardia prominent, rounded.

Vulva transverse slit, flush with body surface, with inner or outer double epiptygmata. Vagina less than half body-width long, not sclerotized, usually dilated inwards as its walls curve out to uterus. Spermathecae rounded, with sperm cells; indistinct in some individuals. Ovaries outstretched, with a single row of oocytes, except in multiplication region. Rectum about half of the anal body width, no post-anal intestinal sac. Tail cylindrical to clavate, with 39 (32–42) annuli along the ventral side; terminal hyaline region 9–11 µm thick, occupying 12.8–17.4% of tail length; tail terminus smooth, with a notch in one specimen. Phasmids large and punctiform, about two µm in diameter, 18.1–31.1 µm posterior to the level of anus. Six incisures of the lateral field extend posterior to phasmids. Juvenile head, pharynx, stylet and tail similar to females; tail cylindrical to clavate, often with thin hyaline region and always with smooth terminus. Lateral field with six incisures in J4 and J3, but only four incisures in J2.

Male. Not found.

Type habitat and locality. Specimens collected from the soil around roots of volunteer wild grapevines ( Vitis sp.) from Belbar village in Uramanat region, Sarvabad county, Kurdistan province, western Iran (coordinates: 35°18'N, 46°22'E).

Type material. Holotype female, one paratype female and five juveniles deposited in the collection of the Department of Plant Protection, College of Agriculture, Shiraz University, Iran; Three female paratypes and two juveniles on the slide number WT 3631 in the Nematode Collection of the Plantenziektenkundige Dienst, Wageningen, The Netherlands.

Etymology. The new species named after the region in Kurdistan province where it was collected: Uramanat.

Discussion. Amplimerlinius uramanatiensis sp. n. is characterized by a medium body length (about 1 mm) and stylet measuring about 30 µm; moderately sclerotized cephalic framework, head with 7–8 annuli, and cylindrical to clavate tail with comparably thin hyaline and smooth terminus.

A. uramanatiensis sp. n. comes close to A. macrurus , A. viciae ( Saltukoglu, 1974) Siddiqi, 1976 , A. hornensis Bello, Mahajan & Zancada, 1987 , A. intermedius ( Bravo, 1976) Siddiqi, 1976 , A. longicauda Castillo, Siddiqi & Gómez-Barcina, 1990 , A. siddiqii Mancini, Cotroneo & Moretti, 1982 , A. omentelus and A. sikkimensis . It differs from all, except A. omentelus and A. sikkimensis , in having smooth tail terminus. Moreover, A. uramanatiensis sp. n. can be distinguished from A. macrurus by having a more distinctly clavate tail, greater extension of the outer margins of cephalic framework into body, slightly longer stylet (29–31 vs. 26–30 µm) and shorter hyaline region (usually 13–15% vs. 17–25% of tail length); from A. viciae in having longer tail (c' = 2.1–2.8 vs. 1.8), shorter hyaline region (13–17% vs. 33% of tail length) and lateral field not widening on tail. It differs from A. hornensis in having smaller body size (average 1.01 vs. 1.24 mm), smaller stylet (29–31 vs. 32–35 µm), longer tail (c' = 2.1–2.8 vs. 1.9–2.2), slightly more anterior vulva (55–57 vs. 58–60) and fewer annuli on tail (32–42 vs. 44–49). It differs from A. intermedius in having smaller body size (0.95–1.08 vs. 1.14–1.55 mm), fewer head annuli (7–8 vs. 8–10), smaller stylet (29–31 vs. 31–39) and fewer annuli on tail (32–42 vs. 53–75); from A. longicauda in having smaller body size (0.95–1.08 vs. 1.18–1.77 mm), shorter tail (c' = 2.1–2.8 vs. 2.9–3.5), more posterior vulva (55–57 vs. 49–55), fewer number of head annuli (7–8 vs. 9–11), smaller stylet (29–31 vs. 32–37 µm) and fewer annuli on tail (32–42 vs. 58–93); from A. siddiqii in having smaller body size (0.95–1.08 vs. 1.27–1.49), longer tail (c' = 2.1–2.8 vs. 1.4–2.3) and shorter stylet (29–31 vs. 32–35); from A. omentelus and A. sikkimensis in having larger body size (0.95–1.08 vs. 0.79–0.88 and 0.67–0.82 mm), longer stylet (29–31 vs. 19–22 and 24–26 µm) and more head annuli (7–8 vs. 0–1 and 5). Further and more detailed comparisons may be made using the diagnostic compendium (Table 3).

Observations on other species. During the present study, A. macrurus and A. paraglobigerus were collected from the rhizosphere of citrus (Babul, Mazandaran province) and forest trees (Kabudval forest, Gorgan, Golestan province), respectively, both in northern Iran (Table 1; Figs. 2 , 3 , 6 ). Furthermore, 21 populations of A. globigerus were collected from different plants and localities in Iran (Table 2; Figs. 4, 6).

The characters of the Iranian population of A. macrurus agree with its description ( Geraert 2011), except for extending the range of MB value (49–55 vs. 52–59). The morphologic and morphometric characters of the collected population of A. paraglobigerus from Iran fit well with the original description ( Castillo et al. 1990), except in having a slightly longer stylet in females (21.5–25.0 vs. 20–23 µm) and males (21.7–23.0 vs. 20–22 µm), and in the ratio of isthmus to basal bulb length (1.0–1.2 vs. 1.5). The morphometrics of the Iranian populations of A. globigerus are consistent with the original description ( Siddiqi 1976), except in wider ranges for b, c, and c' indices, and stylet and spicule lengths (Table 2).

Remarks. Most nematologists (e.g. Siddiqi 2000, Andrássy 2007, Geraert 2011) are in agreement on the synonymy of A. caroli (Fortuner, 1985) Siddiqi, 1986 with A. macrurus . Brzeski (1998), though, pointed out that A. caroli differs in having 4–5 annuli on head (vs. 6–9 in A. macrurus ), and further noted that differences among A. macrurus , A. icarus and A. caroli are minor and that these may actually represent only one valid species. Geraert (2006) noted that the total variation between the smallest A. macrurus and the largest A. icarus is comparable to the published variation in Ditylenchus destructor Thorne, 1945 . Considering the phylogenetic tree obtained using 18S rRNA ( Carta et al. 2010), these two species are likely valid. Moreover, our molecular results ( Ghaderi et al. 2014b), although indicating that A. macrurus and A. icarus are very closely related species, still show a 2.5% nucleotide divergence in sequences of the D2–D3 expansion region of the 28S rRNA gene. Additional distinct differences in morphological characters such as stylet length, tail length, number of tail annuli and shape of outer margins of the cephalic framework support separation of these two species.

Castillo et al. (1990) stated that A. paraglobigerus differs from A. globigerus in having 8–10 annuli in the cephalic region (vs. 6–7), cephalic sclerotisation not appearing bead-like vs. appearing bead-like in optical section, a longer isthmus as compared with the basal bulb length (1.5 times vs. 1–1.1) and female body becoming C-shaped to closed-circle upon relaxation vs. straight to slightly arcuate. Brzeski (1998) pointed out A. paraglobigerus differs from A. globigerus only by having slightly longer laminae of caphalic framework, and further recommended the study of intraspecific variability of both species. However, except in the number of head annuli (none of the 98 females in Iranian populations of A. globigerus were observed to have eight or more annuli up to the end of the framework extension), significant differences were not seen in any of the other mentioned characters between populations of A. globigerus and A. paraglobigerus .

Table 1. Morphometric characters of the Amplimerlinius uramanatiensis sp. n., A. macrurus and A. paraglobigerus collected from Iran (Measurements are in µm).

Table 2. Morphometric characters of females and males of the several populations of Amplimerlinius globigerus , collected from Iran (Measurements are in µm).

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Table 2. continued.

1) strawberry (Torivar and Neshur villages (Sanandej), Chashmidar, Doroud and Karabad villages (Sarvabad) and Bardarashe village (Marivan), all in Kurdistan province); (2) wild grapevine (Belbar village, Sarvabad, Kurdistan); (3) apple (Saqqez, Kurdistan); (4) apricot (Sisakht, Kohgiloyeh and Boyer-Ahmad); (5) grass (Badjgah, Shiraz, Fars); (6) cherry (Qorveh, Kurdistan); (7) almond (Bovanat,); (8) walnut (Yasouj, Kohgiloyeh and Boyer-Ahmad); (9) corn (Basht, Kohgiloyeh and Boyer-Ahmad); (10) grapevine (Ghalat village, Shiraz, Fars); (11) apple (Divandareh, Kurdistan); (12) wheat Yasouj, Kohgiloyeh and Boyer-Ahmad); (13) quince and peach (Dalin village, Shiraz, Fars); (14) walnut (Sepidan, Fars); (15) grapevine (Sisakht, Kohgiloyeh and Boyer-Ahmad); (16) six other populations including fruit trees nursery (Sarabghamish village, Sanandej, Kurdistan), walnut (Oshturan, Hamadan), pepper (Hamadan), corn (Yasouj, Kohgiloyeh and Boyer-Ahmad), cucumber (Shush, Khuzestan) and barley (Sirjan, Kerman).

FIGURE 4. Amplimerlinius globigerus female (A, C–I, K, L, N–S) and male (B, J, M, O). A–B, Pharyngeal region; C–J, Anterior end; K, Cuticle and lateral field, L, Basal pharyngeal bulb and isthmus length variations, N, Reproductive system, O, Body posture; M, P–S, Tail end.

Table 3. Diagnostic compendium of Amplimerlinius species; partly from Bello et al. (1987); morphometrics from published articles plus present study data (measurements in µm, except for L which are in mm).

Cephalic framework sclerotization (HSC = heavily sclerotized, MSC = moderately sclerotized, LSC = lightly sclerotized); inclination of stylet knobs (LAT = lateral, POS = posterior); tail shape (CYL = cylindrical, SCL = subcylindrical); tail terminus (HEM-ANN = hemispherical annulated, HEM-SMO = hemispherical smooth, CLA-ANN = clavate annulated, CLA-ANN = clavate annulated; TRU-ANN = truncated annulated)

Amplimerlinius globigerus closely resembles some species including A. socialis , A. planitierum , A. truncatus and A. umbonatus Ivanova, 1982 . Andrássy (2007) noted that because stylet length is the only difference between A. globigerus and A. socialis , A. globigerus may be a junior synonym of A. socialis . However, stylet length in Iranian populations of A. globigerus overlap somewhat with that of A. socialis . Three other species, namely A. umbonatus , A. planitierum and A. truncatus differ from A. globigerus in areolated lateral field on the female tail, slightly shorter stylet (19–21 µm) and truncate tail, respectively. However, as Geraert (2011) noted, these species are very similar to A. globigerus . Nevertheless, specimens of A. globigerus from Iran very rarely display areolation on the tail and this may be considered as a diagnostic character for separating it from A. umbonatus .

From the drawings in the original description of A. clavicaudatus Choi & Geraert, 1975 , it may be concluded that A. clavicaudatus has a distinct refractive inner cuticle layer and thus, it may be transferred to the genus Paramerlinius Sturhan, 2012 . We propose study of the paratypes of A. caroli , A. planitierum , A. umbonatus and A. truncatus to establish their validity and of those of A. clavicaudatus to clarify its taxonomic position.

Figures

FIGURE 1. Amplimerlinius uramanatiensis sp. n. female (A – I). A – B, Pharyngeal region; C – D, Anterior end; E, Vulva and part of reproductive system; F, Body posture; G – I, Tail end.

FIGURE 2. Amplimerlinius macrurus female (A, C – K) and male (B, H, L). A – B, Pharyngeal region; C – D, Anterior end; E, Reproductive system, F, Cuticle and lateral field, G, Vulva and part of reproductive system; H, Body posture; I – L, Tail end.

FIGURE 3. Amplimerlinius paraglobigerus female (A, C – J) and male (B, H, K). A – B, Pharyngeal region; C – D, Anterior end; E, Reproductive system, F, Cuticle and lateral field, G, Vulva and part of reproductive system; H, Body posture; I – K, Tail end.

FIGURE 5. Amplimerlinius uramanatiensis sp. n. female (A – L). A, Entire body; B – C, Anterior end; D, Pharyngeal region; E, Basal pharyngeal bulb; F, Lateral field; G, Vuvla region; H – I, Phasmid position on tail; J – L, Tail end. Scale-bars: A = 100 µm; B – C, E – I = 10 µm; D = 30 µm; J – L = 20 µm.

FIGURE 6. Amplimerlinius species from Iran: A. uramanatiensis sp. n. (A, E, I); A. macrurus (B, F, J); A. paraglobigerus (C, G, K); A. globigerus (D, H, L). A – D, Anterior end; E – H, Phasmid position on tail; I – L, Tail end. Scale-bars: 10 µm.