Malenchus gilanensis, Jalalinasab & Adeldoost & Abolafia & Heydari, 2019

Jalalinasab, Parisa, Adeldoost, Yaser, Abolafia, Joaquín & Heydari, Ramin, 2019, Description of Malenchus gilanensis n. sp. from Iran, Zootaxa 4638 (4), pp. 562-570 : 563-569

Malenchus gilanensis n. sp.

( Figs 1–4 )

Measurements: See Table 1 .

Description. Female. Body straight or slightly ventrally curved upon fixation, very small and tapering regularly behind vulva. Cuticle with narrow annuli, 0.8–0.9 μm wide at mid-body. Lateral fields with two lines, originating at level of the valve of median pharyngeal bulb and almost reaching the middle of the tail. Lip region narrower than body contour with fine annuli, 4–5 μm wide. Amphidial apertures straight, as in members of subgenus Telomalenchus . Stylet delicate, with rounded knobs directed backwards and conus about one-third of total length. Orifice of dorsal pharyngeal gland about 1 μm behind base of stylet. Pharynx with muscular, valvate median pharyngeal bulb, slender isthmus and pyriform basal pharyngeal bulb offset from intestine. Excretory pore located anterior to or at level of anterior part of basal pharyngeal bulb. Deirids present and located almost at level of excretory pore. Reproductive system monodelphic, ovary outstretched with one row of oocytes. Spermatheca rounded to oval, offset and filled with rounded sperm cells. Post-vulval uterine sac small and about one third of vulval body width long. Vulva sunken in the body, with large lateral flaps. Prophasmids located almost level with the vulva to 9 annuli posterior to vulva. Tail straight, conical with finer annuli posterior to terminus of lateral field.

Male. Similar to females except for reproductive system and rather smaller body. Testis single, spermatogonia arranged in single row. Spicules sickle-shaped. Bursa adcloacal, with crenate margins, very small and apparently the result of partial expansion of the lateral fields. Gubernaculum 4–5 μm long. Tail conical with pointed tip.

Diagnosis and relationships. Malenchus gilanensis n. sp. is characterized by its very small body size, cuticle with narrow annuli (0.8–0.9 μm wide at mid-body), two lines in the lateral fields, originating at level of the valve of median pharyngeal bulb, straight amphidial apertures, stylet 7–8 μm long, vulva sunken in the body and with large lateral flaps, prophasmids located almost level with the vulva to 9 annuli posterior to vulva in females, and adcloacal bursa which can be considered as an outgrowth of the lateral fields in males. This new species is similar to members of the subgenus Telomalenchus , due to the straight amphidial apertures, the position of the prophasmids, and the large lateral vulval flaps but, it differs from these by having two lines in the lateral fields, in addition to other morphological and morphometric differences. Malenchus gilanensis n. sp. is the only member of the subgenus with two lateral cuticular lines ( M. parthenogeneticus and M. leiodermis have four and M. williamsi has six lateral lines in the lateral fields.

This species is also morphologically similar to five known species of the subgenus Malenchus : M. acarayensis Andràssy, 1968 , M. bryanti Knobloch, 1976 , M. parvus Brzeski, 1988 , M. nanellus Siddiqi 1979 and M. truncatus Knobloch, 1976 . This new species can be distinguished from them and other species in the subgenus by having straight amphidial apertures, two lines in the lateral fields, position of prophasmids and very small and undeveloped bursa.

Furthermore, it differs from M. acarayensis mainly by having finer cuticle annuli (0.8–0.9 vs. 1–1.7 μm), pos- terior position of lateral field origin (almost at level of the valve of median pharyngeal bulb vs. 11–15 μm posterior to stylet base), having distinct lateral vulval flaps, posterior position of prophasmids (1–9 annuli posterior to vulva vs. 6–15 annuli anterior to vulva), slightly longer spicules (17–19 vs. 13–16 µm) and smaller, undeveloped bursa (less than one-fifth vs. almost one-third of the tail length). It can be distinguished from M. bryanti by having finer cuticle annuli (0.8–0.9 vs. 1.8–1.9 μm), more posterior lateral field origin (almost at level of the valve of median pharyngeal bulb vs. one quarter to one-third of the procorpus), having distinct lateral vulval flaps, posterior position of prophasmids (1–9 annuli posterior to vulva vs. 6–8 annuli anterior to vulva), longer spicules (17–19 vs. 12–13 µm), slightly longer gubernaculum (4–5 vs. 3–4 µm) and smaller, undeveloped bursa (less than one-fifth vs. almost one quarter of the tail length). It differs from M. parvus by having finer cuticle annuli (0.8–0.9 vs. 1.2–1.5 μm), more posterior position lateral field origin (almost at level of the median bulb valve vs. 11–19 μm from anterior end of the body), anterior position of the excretory pore (located almost at level of the beginning of basal pharyngeal bulb vs. at level of posterior part of basal pharyngeal bulb), distinct lateral vulval flaps, more posterior prophasmids (1–9 annuli posterior to vulva vs. 3–12 annuli anterior to vulva), longer spicules (17–19 vs. 14–15 µm) and slightly longer gubernaculum (4–5 vs. 3–3.5 µm). The new species differs from M. nanellus with more posterior lateral field origin (almost level with the median bulb valve vs. at about half of the procorpus), having distinct lateral vulval flaps, more posterior prophasmids (1–9 annuli posterior to vulva vs. 8–14 annuli anterior to vulva), longer spicules (17–19 vs. 12–15 µm) and longer gubernaculum (4–5 vs. 2–3 µm). Finally, it can be distinguished from M. truncatus by having finer cuticle annuli (0.8–0.9 vs. 1.5 μm), shorter stylet (7–8 vs. 11 µm), more posterior lateral field origin (almost level with the median bulb valve vs. about half the length of the procorpus), more anterior excretory pore (located almost at level with the anterior end of the basal pharyngeal bulb vs. 5–6 μm posterior to basal bulb) and slightly longer spicules (17–19 vs. 15–16 µm).

Etymology. The species epithet “ Gilan ” refers to the province where the specimens of this species were found.

Type locality and habitat. Wood samples of a dead pine tree ( Pinus nigra Arnold ) in Saravan Forest Park, Gilan province (GPS coordinates: 37º 08ʹ 42ʺ N, 49 39ʹ 52ʺ E), northern Iran .

Type material. Female holotype (slide TMG001) and six (four female and two male, slides TMG001 and TMG002) paratypes deposited in the Nematode Collection of the Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. Four female and one male paratypes at the nematode collection of the Departamento de Biología Animal , Biología Vegetal y Ecología, Universidad de Jaén, Spain .

Figures

FIGURE 1. Malenchus gilanensis n. sp. (line drawings).A, Female body; B, Male body; C, Female anterior end; D, Pharyngeal region of female showing origin of the lateral field; E, Vulva region showing post-uterine sac and position of prophasmid; F, Lateral field of female; G, Female posterior body; H, Male posterior body. (Scale bars: A & B = 20 µm, C–H = 10 µm).

FIGURE 2. Malenchus gilanensis n. sp. (light microscope).A, Female anterior body; B, Female anterior body showing origin of the lateral field; C, Basal pharyngeal bulb region; D, Female posterior body (tail); E & F, Prophasmid positions; G, Vulva region showing lateral flap; H, Vulva region showing post-uterine sac; I, Male posterior body showing adcloacal bursa; J, Spicule lateral view. (All scale bars = 10 µm).

FIGURE 3. Malenchus gilanensis n. sp. (scanning electron microscope). A: Anterior body region showing origin of the lateral field and deirid (arrow) region; B–E: Lip region in ventral, frontal, lateral and sublateral views, respectively; F: Lateral view of body showing the deirid (arrow); G: Lateral fields; H: Lateral view of vulva (black arrow) region showing the prophasmid (white arrow); I: Ventral view of vulva showing lateral flaps; J: Anus region.

FIGURE 4. Malenchus gilanensis n. sp. (scanning electron microscope). A: Entire female (white arrow pointing the vulva and black arrow pointing the anus); B: Entire male; C, D: Female posterior end in lateral and ventral views, respectively; E–G: Male posterior end.

Tables

TABLE 1. Morphometrics of Malenchus gilanensis n. sp. from Iran. All measurements are in μm and in the form average ± SD (range).

Characters		Female	Male
	Holotype	Paratype	Paratype
n	-	8	3
L	332	317.8± 18.8 (298–356)	276.3±11.5 (263–283)
L’	276	268.3± 14.3 (250–297)	226.7±8.4 (217–232)
a	25.5	22.3 ± 2.4 (18.2–25.5)	23.7±1.9 (21.9–25.7)
b	4.0	3.8± 0.2 (3.5–4.0)	3.4±0.0 (3.3–3.4)
c	5.9	6.4± 0.4 (5.9–7.0)	5.6±0.1 (5.4–5.7)
c’	7.0	6.1± 0.8 (5.1–7.4)	5.2±0.6 (4.6–5.8)
V or T	63.9	65.6± 1.2 (63.8–66.8)	32.2±0.6 (31.8–32.9)
V’	76.8	77.7± 1.0 (76.4–79.6)	-
Lip region (height)	2	2.0± 0.0 (2–2)	2.5±0.0 (2.5–2.5)
Lip region (width)	5	4.9 ± 0.4 (4–5)	4.7±0.6 (4–5)
Stylet length	8	7.8± 0.4 (7–8)	7.5±0.5 (7–8)
M1	37.5	38.8± 2.0 (37.5–42.9)	40.1±2.7 (37.5–42.9)
Median bulb length	35.0	33.1 ± 1.0 (32–35)	30.3±0.6 (30–31)
MB2	41.7	39.2± 1.3 (38.2–41.7)	37.1±1.8 (35.3–39.0)
Excretory pore – anterior end	65	60.0± 4.8 (51–66)	52.3±2.5 (50–55)
Pharynx length	84	84.5 ± 2.4 (81–89)	82.0±4.4 (77–85)
Annule width	0.9	0.9 ± 0.0 (0.8–0.9)	0.8±0.0 (0.8–0.8)
Vulva – anterior end	212	208.3 ± 8.9 (199–227)	-
Vulva-anus distance	64.0	60.0± 5.6 (51–70)	-
Post uterine vulval sac	3	4.8 ± 1.8 (3–7)	-
Tail length	56	49.5 ± 5.2 (44–59)	49.7±3.2 (46–52)
Tail/vulva-Anus	0.9	0.8± 0.1 (0.8–0.9)
Spicules length	-	-	17.7±1.2 (17–19)
Gubernaculum length	-	-	4.8±0.3 (4.5–5.0)
Bursa length	-	-	16.3±1.2 (15–17)

1 Length of conus as percentage of total stylet length. 2 Median bulb from anterior end (%)