Oligonychus pratensis
Creators: name: Li, Juan
name: Yi, Tian-Ci
name: Guo, Jian-Jun
name: Jin, Dao-Chao
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Tetranychidae
Oligonychus
Oligonychus pratensis

description: Oligonychus pratensis (Banks, 1912)
(Figs. 1–21)
Diagnosis. Female: Dorsocentral setae much longer than distance to setae in next setal row. Dorsal striae almost longitudinal on propodosoma; medial striae on hysterosoma transverse, except for longitudinal striae between setae f 1– f 1, and sometimes between setae e 1– e 1. Genital flap with transverse striae; pregenital striae longitudinal. Peritreme straight, dilated at distal end, bulb-shaped. Palp spinneret suζ sub-conical, 1.5–2 times as long as wide. Leg segment setal formula as follows: coxae 2–2–1–1; trochanters 1–1–1–1; femora 10–6–4–4; genua 5–5–4–4; tibiae 9 (1 φ)–7–6–7; tarsi 13 (1 ω +2dup)–13 (1 ω +1dup)–8 (1 ω)–9 (1 ω). Tarsus I with four tactile setae (l ′ 1, l″ 1, v ′ 2, v″ 1) proximal to the duplex setae, and one solenidion (ω″ 1) on a line with duplex setae. Tibia I with one solenidion (φ) and nine tactile setae; tarsus II with one solenidion (ω″ 1) and three tactile setae (l ′ 1, v ′ 2, v″ 1) proximal to duplex setae; tibia II with seven tactile setae, without solenidion; empodia with two sets of three proximoventral hairs.
Male: Aedeagus bent dorsad; head with blunt anterior projection, posterior projection prolonged and ending in pointed tip; dorsal margin convex; angle of head at an acute angle to shaft. Leg segment setal formula as follows: coxae 2–2–1–1; trochanters 1–1–1–1; femora 10–6–4–4; genua 5–5–4–4; tibiae 9 (4 φ)–7–6–7; tarsi 13 (3 ω +2dup)–13 (1 ω +1dup)–9 (1 ω)–9 (1 ω); empodia I without proximoventral hairs (different from female); empodia II–IV with two sets of three proximoventral hairs (same as female).
Material examined. Six females (slides NO. 1608170201–1608170206), four males (1608170207– 1608170210), five deutonymphs (1608170211–1608170215), six protonymphs (1608170216–1608170221) and five larvae (1608170222–1608170226) were collected from Imperata (Poaceae) at Doupeng Mountain, Badagongshan National Nature Reserve: 109°45′73″E, 29°40′40″N, elevation 1643 m, Zhangjiajie City, Hunan Province, China, on 17 August 2016, by Li Juan and Tian-Ci Yi.
Description. Female (n=6) (Figs. 1–3; 7A–B; 18; 19A–B; 20A–B)
Dorsum (Fig. 1; Fig. 18B). Length of idiosoma including gnathosoma 498–570, excluding gnathosoma 327– 402. Color in life saffron-yellow. Dorsal striae almost longitudinal on propodosoma; hysterosomal striae longitudinal laterally, transverse medially except for longitudinal striae between setae e 1– e 1 and f 1– f 1. Striae between e 1– e 1 and f 1– f 1 roughly form a diamond shape (Fig. 1; Fig. 18B). Strial lobes small and irregular (Fig. 19A). Dorsal setae not set on tubercles, slender, tapering, pubescent (expect for setae h 3 smooth), longer than intervals between their bases.
Setae v 2 72 –81, sc 1 110–120, sc 2 75–91. Distances between setal bases: v 2– v 2 66 –82, sc 1– sc 1 72–96. Hysterosoma with 11 pairs of setae (c 1-3, d 1-2, e 1-2, f 1-2, h 2-3). Setae h 3 slender and smooth (Fig. 2). Measurements of hysterosomal setae: c 1 99–113, c 2 97–108, c 3 95–100, d 1 99–107, d 2 99–109, e 1 95–105, e 2 100–109, f 1 89–100, f 2 75–85, h 3 40–45, h 2 33–37. Distances between setal bases: c 1– c 1 67–74, c 1– d 1 35–64, d 1– d 1 35–76, d 1– e 1 37–63, e 1– e 1 33–43, e 1– f 1 43–71, f 1– f 1 42–55, h 3– h 3 88–109, h 2– h 2 32–36.
Venter (Fig. 2; Fig. 18A; Fig. 20A). Striae transverse between seta 1a to ag, with irregular and close lobes (Fig. 20A). Pregenital striae longitudinal (Fig. 2; Fig.18A). Setae 1a 41–46, 3a 44–53 and 4a 60–65; distances between setae 1a–1a 36–41, 3a–3a 66–74 and 4a–4a 58–68. g 1 33–40, g 2 27–38, anal setae (ps 1-2) subequal in length 17–23. Pregenital setae ag 51–66 nude and longer than genital setae (g 1, g 2) and anal setae (ps 1-2). Length of setae: 1b 51–59, 1c 63–69, 2b 60–68, 2c 79–92, 3b 56–70, 4b 56–70. The distance: ps 1– ps 1 24–46, ps 2– ps 2 21–43, g 1– g 1 24–31, g 2– g 2 84–112, ag–ag 62–70.
Gnathosoma (Figs. 7A–B). Peritreme straight, dilated at distal end forming a small bulb (Fig. 7A). Subcapitular setae m smooth, long 41–47, slightly shorter than m–m 51–58.
All tactile setae on palp smooth. Supracoxal setae e, long 2.5–3.4. Setae l ′ PGe 32–36 in length, about twothirds of palpfemoral setae d PFe 47–57. Palp tibial setae l ′ PTi long 9–14, d PTi, 31–35, l″ PTi 11 9–14. Palp tarsi with seven phaneres: terminal sensillum (suζ) sub-conical, longer than wide, long 5.6–6, 3.4–4.2 in width at base; two lateral eupathidia (ul ′ζ and ul″ζ) subequal in length 7–8; Solenidion ω 3–5, well developed, fusiform; and three tactile nude setae: a 7–8, b 7–10, c 10–11
Legs (Fig. 3; Fig. 20B). Tarsus I with four tactile setae proximal to proximal set of duplex setae, and one solenidion in line with duplex setae, tibia I with one solenidion and nine tactile setae; tarsus II with one solenidion and three tactile setae proximal to duplex setae; tibia II with seven tactile setae. Two pairs of duplex setae on tarsus I, proximal duplex solenidion ω ′ 69–72, distal solenidion ω″ 89–93, ω″ 1 33–50; tarsus II with one set of duplex setae, duplex solenidion ω″ 57–67, ω″ 1 36–42 in length; tarsus III with one proximal solenidion ω ′ 43–50; tarsus IV with one proximal solenidion ω ′ 47–50. One solenidion on tibia I, φ, 53–71. Empodia with two sets of three proximoventral hairs (Fig. 3E–F; Fig. 20B).
All leg setae smooth (Fig. 3). Number of phaneres on legs I–IV (number of solenidia and eupathidia respectively shown in parentheses):
Length of leg segments: trochanter I 39 –43, femur I 85 –91, genu I (43–48, tibia I 48 –54, tarsus I 84 –89; trochanter II 30–36, femur II 57 –67, genu II 37 –45, tibia II 37 –43, tarsus II 68 –77; trochanter III 32 –38, femur III 60 –70, genu III 32 –36, tibia III 4 2–47, tarsus III 66 –80; trochanter IV 2 9–39), femur IV 54 –81, genu IV 36 –46, tibia IV 51 –57, tarsus IV 79 –88.
Male (n=4) (Figs. 4–6; 7C–E; 17F–G; 19C; 20C–D; 21)
Dorsum (Fig. 4). Length of idiosoma including gnathosoma 377–400, excluding gnathosoma 264–294. Prodorsum with longitudinal striae. Medial hysterosoma transversely striated. Shape of dorsal setae as in female. Setae ps 1 often inserted dorsally to dorsolaterally (Fig. 17F–G), depending on mounting. Length of setae: v 2 49 –51, sc 1 79–85, sc 2 60–63, c 1 65–71, c 2 70–72, c 3 65–73, d 1 72–73, d 2 76–80, e 1 66–68, e 2 73–75, f 1 48–52, f 2 44–49, h 3 18–21, h 2 18–23. Distances between setal bases: v 2– v 2 48 –53, sc 1–s c 1 60–63, c 1– c 1 52–56, c 1– d 1 34–37, d 1– d 1 50–51, d 1– e 1 32–37, e 1– e 1 27–29, e 1– f 1 23–2), f 1– f 1 26–30, h 2– h 2 23–26, h 3– h 3 60–64.
Venter (Fig. 5). Striae transverse. And the interval of striate in hysterosoma more broader than in propodosoma; all ventral setae smooth and thin: 1a 30–32, 1b 38–40, 1c 43–55, 2b 44–46, 2c 60–63, 3a 29–30, 3b 40–48, 4a 41–44, 4b 42–45, ag 44–54, g 1 15–17, g 2 15–16, ps 1 18–21, ps 2 15–17.
Distances between setal bases: 1a–1a 25–27, 3a–3a 44–47, 4a–4a 34–41, g 1– g 1, 22–27, g 2– g 2 29–33, ps 2– ps 2 29–31, ps 2– ps 2 30–32, ag–ag 35–40.
Gnathosoma (Fig. 7C). Subcapitular seta m 30–35, slightly shorter than distance m–m 38–39; supracoxal seta e 2–2. Setae d PFe stubby, shorter and thicker than in female, 8–9 in length and 2.8–3.2 in diameter at base. Palp tarsus with cone-shaped spinneret, suζ 5.2–5.6 subequal in female suζ 5.6–6 in length; and 2.8–3.2 in diameter at base; single solenidion, ω 4–4.3 long, two eupathidia (ul ′ζ and ul″ζ) subequal in length 5–6, three normal setae, b 5–7, a 5–7, c 6–7. Measurements of setae on palp: l ′ PGe 24–26, l ′ PTi 7–8, l″ PTi 16–17, d PTi 20–22.
Legs (Fig. 6). Tarsus I with two solenidia and four tactile setae proximal to proximal set of duplex setae and one solenidion in line with duplex setae, tibia I with four solenidia and nine tactile setae; tarsus II with one solenidion and three tactile setae proximal to duplex setae; tibia II with seven tactile setae. Two pairs of duplex setae on tarsus I distal and adjacent, proximal duplex solenidion ω ′ 45–55, distal solenidion ω″ 60–63, ω″ 1 32–35; tarsus II with one set of duplex setae, duplex solenidion ω″ 47–49, ω″ 1 28–34; tarsus III with one proximal solenidion ω ′ 38–42; tarsus IV with one proximal solenidion ω ′ 39–41. Four solenidia on tibia I: φ 43–50, φ ′ 1 26– 30, φ″ 1 29–32, φ″ 2 31–33. Empodia I without proximoventral hairs (Fig. 6E; Fig. 20C); empodia II–IV with two sets of three proximoventral hairs (Fig. 6F; Fig. 20D).
All leg setae smooth (Fig. 6). Number of phaneres on legs I–IV (the number of solenidia and eupathidia respectively shown in parentheses):
Lengths of leg segments: trochanter I 36 –39, femur I 60 –67, genu I 31–35, tibia I 39 –42, tarsus I 56 –59; trochanter II 28–33, femur II 46 –50, genu II 29–34, tibia II 32 –46, tarsus II 48 –58; trochanter III 26–30, femur III 43 –48, genu III 25–30, tibia III 31–33, tarsus III 50 –53; trochanter IV 29–32, femur IV 54 –57, genu IV 35 –39, tibia IV 35 –39, tarsus IV 46 –55.
Aedeagus (Figs. 7D–E; Fig. 19C; Fig. 21B). Aedeagus bent dorsad; head with blunt anterior projection, posterior projection prolonged and ending in pointed tip; dorsal margin convex; angle of head at an acute angle to shaft, dorsal surface of knob obtusely angulate and axis knob forms a slight angle with angle of shaft (Fig. 21B).
Deutonymph (n=5) (Figs. 8–10; 17B)
Dorsum (Fig. 8). Body length including gnathosoma 313–407, excluding gnathosoma 239–320. Striation similar to female except with transverse striae between setae e 1 -e 1. Striae around bases of setae f 1 with heliciform shape (Fig. 8). Prodorsal setae shape as in female. Length of setae: v 2 49 –57, sc 1 76–95 sc 2 52–67, c 1 61–80, c 2 65– 80, c 3 62–78, d 1 60–77, d 2 64–78, e 1 61–74, e 2 62–78, f 1 52–66, f 2 49–56, h 3 20–22, h 2 26–33. Distances between setal bases: v 2– v 2 51 –61, sc 1– sc 1 63–78, c 1– c 1 58–68, c 1– d 1 25–47, d 1– d 1 55–68, d 1– e 1 23–36, e 1– e 1 24–36, e 1– f 1 29– 38, f 1– f 1 20–28, h 3– h 3 54–75, h 2– h 2 25–28.
Venter (Fig. 9). Striae mostly transverse, all ventral setae smooth and thin: 1a 25–36, 1b 29–47, 1c 44–50, 2b 34–54, 2c 50–64, 3a 26–35, 3b 37–47, ag 38–49, g 1 21–25, ps 1 12–15, ps 2 11–16. Distances between setal bases: 1a–1a 26–32, 3a–3a 48–58, 4a–4a 40–52, g 1– g 1 37–51, ag–ag 39–45, ps 1– ps 1 11–25, ps 2– ps 2 14–30.
Gnathosoma (Fig. 17B). Subcapitular seta m smooth 32–37, shorter than distance m–m 31–47; supracoxal seta e 2.5 –3.3. Setae d PFe 31–44. Setae l ′ PGe long 23–32, d PTi 26–30, l ′ PTi 9–12, l″ PTi 16–22. Palp tarsus with coneshaped spinneret, length suζ 4.7–5.3. Solenidion ω fusiform, length 4.5–5.6, eupathidia (ul ′ζ and ul″ζ) subequal in length 5.6–7, three normal setae: a 5–7, b 5–7, c 6.8–9.
Legs (Fig. 10). Two pairs of duplex setae of tarsus I: ω ′ 40–50, ω″ 62–75, one solenidion ω″ 1 in line with duplex setae, long 23–29; tarsi II: ω″ 35–46; tibiae I with one solenidia φ 39–41; tarsus III with one solenidion ω ′ 24–33.
All leg setae smooth (Fig. 10). Number of phaneres on legs I–IV (the number of solenidia and eupathidia respectively show in parentheses):
Lengths of leg segments: trochanter I 29–38, femur I 56 –65, genu I 22–35, tibia I 28–36, tarsus I 45 –62; trochanter II 28–31, femur II 41 –63, genu II 22–33, tibia II 23–32, tarsus II 42 –51; trochanter III 24–32, femur III 37 –46, genu III 23–27, tibia III 25–32, tarsus III 41 –52; trochanter IV 26–31, femur IV 42 –60, genu IV 21–30, tibia IV 24–36, tarsus IV 44 –56.
Protonymph (n=6) (Figs. 11–13; 17A)
Dorsum (Fig. 11). Body length including gnathosoma 258–341, excluding gnathosoma 197–275. Striae and shape of dorsal setae similar to deutonymph except setae h 2 smooth; setae h 3 and h2 located ventrally. Length of setae: v 2 45 –56, sc 1 68–78, sc 2 46–54, c 1 52–65, c 2 53–65, c 3 49–61, d 1 51–64, d 2 58–65, e 1 46–57, e 2 50–62, f 1 43– 54, f 2 34–47, h 3 21–25, h 2 16–26. Distances between setal bases: v2–v 2 51 –56, sc 1– sc 1 63–69, c 1– c 1 52–56, c 1– d 1 19– 33, d 1– d 1 51–60, d 1– e 1 19–36, e 1– e 1 26–33, e 1– f 1 25–33, f 1– f 1 17–22, h 3– h 3 39–53, h 2– h 2 16–36.
Venter (Fig. 12). The striae mostly transverse, all ventral setae smooth and thin: 1a 23–30, 1b 33–38, 1c 36– 46, 2b 41–50, 3a 27–32, 3b 31–39, ag 31–39, ps 1 10–13, ps 2 9–14. Distances between setal bases: 1a–1a 23–28, 3a–3a 43–53, ag–ag 29–35, ps 1– ps 1 11–16, ps 2– ps 2 12–20.
Gnathosoma (Fig. 17A). Subcapitular setae m smooth, length 26–30, shorter than distance m–m 29–35; Supracoxal setae e 2.4 –3. Setae d PFe 27–36. Setae l ′ PGe 20–27, d PTi 18–23, l ′ PTi 16–22, l″ PTi 9–12; palp tarsus with cone-shaped spinneret, suζ 4–5, twice as long as width 2–3. Single solenidion, ω 3.2–4.7, two eupathidia (ul ′ζ and ul″ζ) subequal in length 4–5, three normal setae, a 5–6, b 4–5, c 5–6.
Legs (Fig. 13). Two pairs of duplex setae of tarsi I medial and adjacent: ω ′ 25–37, ω″ 50–61 in length; tarsi II: ω″ 32–37 in length; tibiae I with one solenidion φ 34–40.
All leg setae smooth (Fig. 13). Number of phaneres on legs I–IV (the number of solenidia and eupathidia respectively show in parentheses):
Lengths of leg segments: trochanter I 22–28, femur I 43 –50, genu I 24–27, tibia I 24–30, tarsus I 44 –49; trochanter II 21–28, femur II 32 –38, genu II 20–26, tibia II 18–26, tarsus II 35 –40; trochanter III 21–25, femur III 24–36, genu III 18–21, tibia III 22–25, tarsus III 34 –39; trochanter IV 19–26, femur IV 24–36, genu IV 18–21, tibia IV 22–25, tarsus IV 33 –36.
Larva (n=5) (Figs. 14; 15; 17C)
Dorsum (Fig. 14). Body length including gnathosoma 206–248, excluding gnathosoma 143–200. Dorsal striation and setal shape similar to protonymph. Length of setae: v 2 45 –51, sc 1 61–65, sc 2 42–51, c 1 47–53, c 2 43–47, c 3 45–49, d 1 44–48, d 2 43–47, e 1 44–47, e 2 44–50, f 1 37–43, f 2 35–40, h 3 20–25, h 2 19–24. Distances between setal bases: v 2– v 2 44 –49, sc 1– sc 1 56–63, c 1– c 1 44–53, c 1– d 1 22–33, d 1– d 1 36–43, d 1– e 1 22–32, e 1– e 1 22–25, e 1– f 1 23–34, f 1– f 1 11–13, h 3– h 3 34–44, h 2– h 2 10–12.
Venter (Fig. 15). Venter almost entirely transversely striate. Ventral setae thin, smooth: 1a 22–26, 1b 29–32, 3a 22–28, ps 1 9–10, ps 2 9–10. Distances between setal bases: 1a–1a 21–26, 3a–3a 44–51, ps 1– ps 1 7–11, ps 2– ps 2 6– 12.
Gnathosoma (Figs. 17C). Seta d PFe 25–29, l ′ PGe 17–22, d PTi 22–25, l ′ PTi 7–8, l″ PTi 14–19; palpal tarsi with slender cone-shaped spinneret suζ 4.3–4.8 in length and 1.1–1.5 in diameter at base; single solenidion ω 3.5– 4, two eupathidia ul ′ζ 4–5.5, ul″ζ 4.9–5.3 and three normal setae, a 4–4.5, b 4–5 c 4.6–5.2.
Legs (Fig. 16). Segments of legs stubby. Single pair of duplex setae on tarsi I medial. Tarsi I and tibia I with one solenidion respectively, tarsi I ω″ 35–55; tibiae I φ 33–34. Tarsi II with one duplex setae, ω″ 32–38.
All leg setae smooth (Fig. 16). Number of phaneres on legs I–IV (the number of solenidia and eupathidia respectively show in parentheses):
Length of leg segments: trochanter I 21–29, femur I 30–36, genu I 16–18, tibia I 21–25, tarsus I 35 –38; trochanter II 18–22, femur II 26–30, genu II 16–19, tibia II 14–18, tarsus II 35 –38; trochanter III 16–20, femur III 19–29, genu III 15–20, tibia III 16–19, tarsus III 29–31.
FIGURE 18. Oligonychus pratensis. Photographs. A, shoWing pregenital striae and genitoanal region; B, striae of dorsum betWeen setae f 1– f 1. Scale bars 10 µm
Remarks. Pritchard & Baker (1955) pointed out that the adult females of O. pratensis are pale yellowish or straw-colored, and have dusky spots along each side. In our work, we observed that females of O. pratensis were a saffron-yellow color with white (somewhat pellucid) legs. The nymphs are a greenish yellow color and larvae are pellucid, with two dark spots in the idiosoma. Both Oryza spp. (10 species) and Zea spp. (19 spp.) are common host plants for Oligonychus. We found all life stages of O. pratensis from Imperata (Poaceae), which is also a common host plant (6 spp.) (Migeon & Dorkeld 2006 –2017). We note that the typical host of O. pratensis is Poaceae (Tuttle & Baker, 1968? Tuttle et al., 1976; Pritchard & Baker, 1955; Ma & Yuan, 1980), as it is for many species of Oligonychus.
O. pratensis belongs to the pratensis species group, as defined by Pritchard & Baker (1955), by having: eight or nine tactile setae on tibia I; tarsus I usually with two tactile setae on venter beyond first duplex; empodium with only three pairs of proximoventral hairs; integumentary striae transverse between third pair (e 1– e 1) of dorsocentral setae, longitudinal between f 1– f 1; and peritreme ending in a simple bulb. However, our specimens showed longitudinal striae between e 1– e 1, but other descriptions (Pritchard & Baker, 1955; Tuttle & Baker, 1968) do not show this. This difference was consistent, and its presence suggests it could represent another species, but we are reluctant to propose another species when all other features match O. pratensis well.
Furthermore, species identification in the pratensis group is complex, and the group is in need of revision. For example, at first we considered our species as O. shinkajii Ehara, 1963, a species considered as a junior synonym of O. modestus (Banks, 1900) by Ehara & Gotoh (2007). O. modestus and O. shinkajii are similar to O. pratensis by having a similar aedeagal shape: the aedeagus of both species has a small anterior projection, a pointed posterior projection (with no down-curve at the tip), and head angled acutely with the shaft. Despite these similarities, the aedeagus of O. modestus is significantly different from that of O. pratensis and O. shinkajii.
The aedeagus of O. modestus is distinctive in that the distal end is scarcely enlarged, and the dorsal surface of the tiny knob is curved and parallel to the axis of the shaft (Fig. 21D). In contrast, the aedeagus of O. pratensis and O. shinkajii bears a knob with an anterior, small and rather acute mucro, the dorsal surface is obtusely angulate, the axis of the knob forms a slight angle with that of the shaft, and the posterior projection is long (Fig. 21A). Ehara & Gotoh (2007) recognized O. shinkajii as a junior synonym of O. modestus on the basis of aedeagal similarities. However, in light of the data presented, we conclude that O. shinkajii should not be considered as a synonym of the species O. modestus, i.e. they are two separate species. It seems possible that O. shinkajii and O. pratensis could be synonyms as they appear to share numerous features, including aedeagal morphology. However, pending examination of type specimens for both specimens in the context of broad revisionary work, we retain these species as separate. Here, we considered our specimens O. pratensis because of the greater angle between the shaft and head of the aedeagus (ca. 30°) compared to O. shinkajii, which is usually shown with a much smaller angle.
–* means O. pratensis lacking the setae v ′ 1, compared with O. afrasiaticus and O. saccharinus.
description: Published as part of Li, Juan, Yi, Tian-Ci, Guo, Jian-Jun & Jin, Dao-Chao, 2018, Ontogenetic development and redescription of Oligonychus pratensis (Banks, 1912) (Acari: Tetranychidae), pp. 349-375 in Zootaxa 4486 (3) on pages 350-372, DOI: 10.11646/zootaxa.4486.3.7, http://zenodo.org/record/1437118