Mirza, Jawwad Hassan ¹ ; Kamran, Muhammad ² and Alatawi, Fahad Jaber ³

¹Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.
²Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.
³✉ Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.

2024 - Volume: 64 Issue: 4 pages: 1052-1062

ZooBank LSID: 689664CD-E233-491A-B12D-EE1B832E4AC6

Original research

Keywords

Abstract

Introduction

The spider mite genus Schizotetranychus Trägårdh (Acari: Tetranychidae) is the fourth largest (118 spp.) in the subfamily Tetranychinae Berlese (Bolland et al. 1998; Migeon and Dorkeld 2006–2024). The members of the genus have economic importance with some well distributed species sometimes damaging agronomic crops i.e., S. baltazari Rimando (citrus green mites), S. asparagi (Oudemans) (pineapple mite) and S. oryzae Rossi de Simons (rice mite) (Jeppson et al. 1975).

The genus Schizotetranychus was erected by Trägårdh (1915), based on Tetranychus schizopus Zacher (1913) as the type species, reported from Salix sp. (Salicaceae) in Germany (Pritchard and Baker 1955). The species identity in the genus is challenging and mostly requires specimens of both sexes. Flechtmann (2012), based on female morphological characters, classified the species of this genus into seventeen arbitrary groups along with a classification key to groups. The female morphological characters for the grouping included the shape of idiosoma, length of dorsocentral body setae (c₁ , d₁ , e₁ ) and total number of tactile setae on tibia I (Flechtmann 2012). Some regional keys for the identification of Schizotetranychus species also exist (Baker and Pritchard 1960; Meyer 1987; Mahdavi and Asadi 2015).

In this study, the genus Schizotetranychus is recorded for the first time from Saudi Arabia with a new species, S. astragalus sp. nov. described and illustrated based on females and males collected from Astragalus sp. (Fabaceae). A diagnostic key to Schizotetranychus species of the group 15 is also provided.

Material and methods

The mite specimens were collected by shaking the plant foliage parts over a white sheet of paper and preserved in small vials with 70% Ethanol. The mounted specimens were identified under a phase contrast microscope (BX51, Olympus®, Japan). Different mite body parts were imaged by using an Auto-Montage software system (Syncroscopy, Cambridge, UK) attached to a phase contrast microscope (DM2500, Leica®, Germany). The illustrations were drawn with Adobe Illustrator (Adobe System Inc., San Jose, CA, USA). All measurements are given in micrometers (μm). The measurements are presented for the holotype followed by the range for paratypes in parentheses. The morphological terminology used in this study followed Lindquist (1985). All holotype and paratypes have been deposited in the King Saud University Museum of Arthropods (KSMA, Acarology section), Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.

Taxonomy

Family Tetranychidae Donnadieu

Subfamily Tetranychinae Berlese

Tribe Tetranychini Reck

Genus Schizotetranychus Trägårdh

Schizotetranychus Trägårdh, 1915: 277

Type-species — Tetranychus schizopus Zacher 1913: 40.

Diagnosis — Based on the Pritchard and Baker 1955; Meyer 1987

The new species, Schizotetranychus astraglus sp. nov. belongs to the group 15 of the Schizotetranychus species, following Flecthmann (2012) based on tibiae of leg I in female with seven tactile setae and a sensory seta, dorsocentral hysterosomal setae c₁ , d₁ and e₁ longer than interval to the base of seta next behind, reaching past the first seta behind and body shape oval. The group 15 is comprised of six species based on the classification of Flecthmann (2012).

Schizotetranychus astragalus sp. nov.

ZOOBANK: D5AF996E-5004-4F82-8186-059ADA9B533A

(Figures 1−8)

Type material

Female holotype, four female and three male paratypes ex. Astragalus sp. (Fabaceae), Jubail, 27°4′16″N, 49°35′13″E, Altitude 1843 m, 18 October 2019, coll. M. Kamran and H.M.S. Mushtaq.

Diagnosis

Female — Idiosoma oval, ratio of body length to width less than 2 (1.59); 5 tactile setae on tibia II–IV; peritremes ending in simple bulb; dorsal body setae simple slender and longer than distances between consecutive setae; medial opisthosoma with transverse striations without lobes.

Male — Aaedeagus upturned, sigmoid and neck at an obtuse angle to the shaft.

Description (n=8)

Female (n=5)

Idiosoma not elongate; length of body is more than width (L:W = 1.59); length of idiosoma (excluding gnathosoma) 298 (290–309), including gnathosoma 345 (332–357), maximum width at the level of c_1-3 setae 189 (183–197).

Dorsum — (Figure 1) — Dorsal propodosomal striations entirely longitudinal; dorsal hysterosomal integument with coarse transverse striae on dorsocentral area, laterally with longitudinal striae, without lobes; idiosomal dorsum with 13 pairs of long, slender, tapering tips setae; dorsocentral hysterosomal setae longer than distances between consecutive setae and well crossing second setae behind; second pair of propodosomal setae (sc₁ ) longer than other dorsal setae; dorsocentral setae (c₁ , d₁ , e₁ , f₁ ) inline and close in distance. Lengths of dorsal setae: v₂ 66 (62–71), sc₁ 75 (71–79), sc₂ 48 (43–53), c₁ 66 (62–69), c₂ 59 (56–64), c₃ 54 (51–58), d₁ 65 (62–68), d₂ 66 (63–70), e₁ 57 (53–60), e₂ 51 (48–54), f₁ 48 (45–51), f₂ 45 (42–48), h₁ 49 (44–53); distances between dorsal setae: v₂ –v₂ 44 (41–48), sc₁ –sc₁ 90 (86–94), sc₂ –sc₂ 159 (151–168), c₁ –c₁ 25 (22–28), c₂ –c₂ 108 (103–115), c₃ –c₃ 180 (171–186), d₁ –d₁ 25 (22–27), d₂ –d₂ 123 (117–129), e₁ –e₁ 25 (22–27), e₂ –e₂ 118 (115–123), f₁ –f₁ 23 (21–26), f₂ –f₂ 82 (78–86), h₁ –h₁ 21 (20–23), v₂ −sc₁ 36 (33–39), sc₁ −sc₂ 52 (48–55), sc₂ −c₃ 54 (50–58), sc₂ −c₂ 44 (42–48), sc₂ −c₁ 50 (46–54), c₁ −c₂ 48 (44–54), c₂ −c₃ 33 (31–35), c₁ −d₁ 36 (33–39), c₂ −d₂ 49 (46–53), d₁ −e₁ 46 (42–48), d₂ −e₂ 57 (51−63), e₁ −f₁ 30 (27–32), e₂ −f₂ 45 (42–48), f₁ −f₂ 41 (37–43), f₁ −h₁ 45 (42–48), f₂ −h₁ 33 (31–35). Setae f₁ dorsally normal in position, equally spaced than other dorsocentral setae.

Venter — (Figure 2) — Idiosoma ventrally with transverse striations from setae 1a to ag, genital flap with transverse striations and pregenital area with oblique to longitudinal striation. Lengths of ventral setae: 1a 40 (37–42), 3a 35 (33–37), 4a 38 (35–42), 1b 37 (35–40), 1c 40 (38–43), 2b 37 (35–39), 2c 41 (38–43), 3b 36 (33–37), 4b 37 (34–39); distances between setae: 1a−1a 24 (22–26), 1b−1c 30 (27–32), 2b−2c 25 (24–27), 3a−3a 49 (46–52), 4a−4a 28 (25−30); ag 39 (36–42), ag−ag 49 (47–53); g₁ 26 (23–28), g₂ 29 (27–32), g₁ −g₁ 26 (23–29), g₂ −g₂ 50 (47–54); ps₁ 15 (13–17), ps₂ 16 (14–18); distances between ps₁ −ps₂ 8 (7–9), ps₁ −ps₁ 37 (35–39), ps₂ −ps₂ 27 (25–29); h₂ 32 (30–34), h₃ 30 (28–35), h₂ −h₂ 65 (62–68), h₃ −h₃ 37 (35−40).

Gnathosoma — (Figure 3) — Stylophore rounded anteriorly with longitudinal parallel striations. Peritremes slender, straight, ending in a small bulb (Figure 1B). Subcapitular setae m 33 (30–35), m−m 27 (25–28). Palp setation typical, palp femur and genu each with one setae, d 48 (45–52), l″ 24 (22–26), respectively; palp tibia with three setae, d 25 (21–27), l″ 21 (19–23), l′ 13 (12–14), palp tarsus 17 long, 13 wide, with three simple setae a 8 (7–9), b 7 (7–9), c 8 (7–9); three eupathidia suζ 8 (7), ul″ζ = ul′ζ 5 (4–6), a solenidion ω 2 long; terminal sensillum of palp tarsus (suζ) conical, long, pointed, about 2 times as long as wide near base (Figure 3).

Legs — (Figures 4A–D) — Length of legs I−IV (without coxae): 173 (166–179), 131 (126–138), 147 (141–155), 171 (165–176) respectively; leg I 173 (166–179): trochanter 19 (16–23), femur 54 (50–56), genu 34 (32–38), tibia 28 (25–29), tarsus 36 (32–39); leg II 131 (126–138): trochanter 17 (15–19), femur 55 (52–59), genu 28 (26–31), tibia 22 (20–25), tarsus 29 (27–31); leg III 147 (141–155): trochanter 23 (21–25), femur 34 (33–38), genu 25 (23–28), tibia 28 (26–30), tarsus 38 (35–40); leg IV 171 (165–176): trochanter 30 (27–32), femur 48 (45−50), genu 27 (25−30), tibia 31 (28–33), tarsi 35 (32–38). Setal counts on legs I−IV (solenidion in parentheses): coxae 2–2–1–1, trochanters 1–1–1–1; femora 10–6–2–2; genua 5–5–3–3; tibiae 7(1φ)–5–5–5; tarsi 12+(1ω)+2 dupl–11(1ω)+1 dupl−7(1ω)–7(1ω). Empodia I–IV similar, empodia split into 2 uncinate claws. Tarsus I with three tactile setae and a solenidion proximal to proximal set of duplex setae, the tactile seta of both the proximal and distal duplex setae 0.28 times the length of respective sensory seta. Tarsus II with four tactile and a solenidion proximal to duplex setae, the tactile seta 0.24 times the length of the sensory seta.

Male (n = 3)

Length of idiosoma (excluding gnathosoma), 254–271, including gnathosoma 310–327, maximum width at level of c_1-3 setae 154–173.

Dorsum — (Figure 5) — Propodosomal and hysterosomal striations, shape and number of dorsal body setae same as in female; lengths of dorsal setae: v₂ 30–35, sc₁ 37–43, sc₂ 30–35, c₁ 32–38, c₂ 31–35, c₃ 25–30, d₁ 32–38, d₂ 28–32, e₁ 30–35, e₂ 24–28, f₁ 25–28, f₂ 21–25, h₁ 23–28; distances between dorsal setae: v₂ –v₂ 36–40, sc₁ –sc₁ 55–61, sc₂ –sc₂ 101–108, c₁ –c₁ 21–29, c₂ –c₂ 86–98, c₃ –c₃ 151–159, d₁ –d₁ 22–27, d₂ –d₂ 93–110, e₁ –e₁ 22–26, e₂ –e₂ 70–79, f₁ –f₁ 21–27, f₂ –f₂ 46–54, h₁ –h₁ 16–20, v₂ −sc₁ 33–39, sc₁ −sc₂ 35–39, sc₂ −c₃ 50–58, sc₂ −c₂ 44–53, sc₂ −c₁ 49–59, c₁ −c₂ 20–24, c₂ −c₃ 31−35, c₁ −d₁ 31–35, c₂ −d₂ 40–43, d₁ −e₁ 28–33, d₂ −e₂ 33–38, e₁ −f₁ 21–25, e₂ −f₂ 28–35, f₁ −f₂ 17–20, f₁ −h₁ 21–25, f₂ −h₁ 17–20.

Venter — (Figures 6, 8) — Aedeagus bent dorsad to form sigmoid shape, with acuminate tip, distal end pointing upward and outward, and neck at an obtuse angle to the shaft (Figure 8). Idiosoma ventrally with transverse striations; Lengths of ventral setae: 1a 37–42, 3a 28–33, 4a 33–38, 1b 35–40, 1c 38–43, 2b 35–39, 2c 38–43, 3b 33–37, 4b 34–39; distances between setae 1a−1a 23–28, 1b−1c 25–28, 2b−2c 24–27, 3a−3a 43–48, 4a−4a 24–28;g₁ 23−28, g₂ 27−32, g₁ −g₁ 23–29, g₂ −g₂ 47–54; ps₁ 10–13, ps₂ 10–12; ps₁ −ps₂ 6–8, ps₁ −ps₁ 15–18, ps₂ −ps₂ 11–14; h₂ 21−24, h₃ 18−23, h₂ −h₂ 32−38, h₃ −h₃ 35−40.

Gnathosoma — Stylophore and peritremes as in female. Subcapitular setae m 30–35, m−m 23–28. Palp femur and genu each with one seta, d 45–52, l″ 22–26, respectively; palp tibia with three setae, d 7–8, l″ 19–22, l′ 16–20 and a palp tibial claw; palp tarsus 17 long, 13 wide, with three simple setae a 7–9, b 7–9, c 7–9; three eupathidia suζ 7, ul″ζ = ul′ζ 4–6, a solenidion ω 2 long; terminal sensillum of palp tarsus (suζ) conical, long, pointed, about 2 times as long as wide near base.

Legs — (Figures 7A & B) — Length of legs I−IV (without coxae): 142–155, 120–138, 132–145, 138–150 respectively; leg I 142–155: trochanter 17–24, femur 47–53, genu 28–33, tibia 23–27, tarsus 26–30; leg II 120–138: trochanter 12–15, femur 42–49, genu 24–28, tibia 20–25, tarsus 25–30; leg III 132–145: trochanter 23–26, femur 39–44, genu 20–24, tibia 22–27, tarsus 26–31; leg IV 138–15: trochanters 22–32, femur 45–50, genu 25–30, tibia 26–33, tarsi 32–34. Chaetotaxy on legs I−IV (solenidia in parentheses): coxae 2–2–1–1, trochanter 1–1–1–1; femora 10–6–2–2; genua 5–5–3–3; tibiae 7(2φ)–5(1φ)–5–5; tarsi 11(2ω)+2 dupl.–10(1ω)+1 dupl.–7(1ω)–7(1ω).

Immature stages — Unknown.

Etymology

The specific epithet refers to the genus name of the host plant,'Astragalus' from which the type specimens were collected.

Remarks

Schizotetranychus astragalus sp. nov., is morphologically close to S. recki Ehara (1957) by having the characteristics of dorsocentral hysterosomal setae c₁ , d₁ and e₁ longer than interval to base of seta next behind, Tibia of leg I of female with 7 tactile and one sensory setae and simple peritremes. However, the new species differs from the S. recki by the distinct differences of leg chaetotaxy on tibia II¬IV (5-5-5 vs. 6-3-4), number of setae proximal to proximal duplex setae on tarsus I (three vs two) and tarsus II (four vs one) and shape of peritremes (straight vs. bent distally).

Flecthmann (2012) placed the species S. schizopus (Zacher) in the group 15 and provided a note stating that Ehara (1957) reported this species to have 8 or 9 tactile setae on tibiae I of females. But this group includes species having tibiae I with 7 tactile setae. The original description (Zacher 1913) and re-descriptions (Garman 1940; Reck 1948; McGregor 1950; Pritchard and Baker 1955; Baker and Tuttle 1994; Ehara 1999) of this species do not bring much help towards leg setal counts. It is suggested that S. schizopus should not belong to the group 15 of Schizotetranychus species. Hence, it is not included in the remarks and has been excluded from the identification key.

Key to Schizotetranychus species of the group 15

1. Peritremes anastomosing
...... S. cajani Gupta

— Peritremes simpel
...... 2

2. Peritremes simple ending bulbous distally
...... 3

— Peritremes recurved/hooked distally
...... 5

3. Tibia II-¬IV 6-4-3
...... S. recki Ehara

— Tibia II-¬IV 5-5-5
...... S. astragalus sp. nov. Alatawi & Kamran

4. Male aedeagus tapering and curving evenly dorsad at an obtuse angle, not distinctly sigmoid
...... S. filifolius Meyer

— Male aedeagus bends upward at right angle and tapers abruptly, distinctly sigmoid
...... 7

5. Aedeagal head distinct, bending at right angle to vertical part of shaft
...... S. rhynosperus Flechtmann & Baker

— Aedeagal head indistinct, bending only slightly
...... S. arcuatus Meyer

Disclosure statement

No potential conflict of interest was reported by the author(s).

Acknowledgments

The authors extend their appreciation and special thanks to respected Carlos Holger Wenzel Flechtmann (University of São Paulo, Brazil), for providing useful literature. The authors would like to extend their sincere appreciation to the researchers supporting the project at King Saud University, Riyadh, Saudi Arabia, for financial support.

Funding

The authors would like to extend their sincere appreciation to the Researchers Supporting Project number (RSPD2024R807), King Saud University, Riyadh, Saudi Arabia.

References

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