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Genus Eryngiopus Summers (Acari: Trombidiformes: Stigmaeidae) from Saudi Arabia; a new record and redescription of E. discus Meyer, with a key to the world species

Rehman, Muneeb Ur1 ; Kamran, Muhammad2 and Alatawi, Fahad J.3

1Acarology Laboratory, Department of Plant Protection, College of Food & Agriculture Sciences, King Saud University, 11451, P.O. Box 2460, Riyadh, Saudi Arabia.
2Acarology Laboratory, Department of Plant Protection, College of Food & Agriculture Sciences, King Saud University, 11451, P.O. Box 2460, Riyadh, Saudi Arabia.
3✉ Acarology Laboratory, Department of Plant Protection, College of Food & Agriculture Sciences, King Saud University, 11451, P.O. Box 2460, Riyadh, Saudi Arabia.

2018 - Volume: 58 Issue: 3 pages: 655-664

https://doi.org/10.24349/acarologia/20184262
ZooBank LSID: F75FB617-F28C-4516-ACC9-9F212FD054DE

Keywords

bakeri, gracilis, predatory mites, species groups, stigmaeids

Abstract

Eryngiopus discus Meyer, 1969 (Acari: Trombidiformes: Stigmaeidae), the first species of the genus Eryngiopus Summers recorded from Saudi Arabia, is re-described and illustrated. The specimens of this species were collected from foxtail grass Cenchrus sp. (Poaceae) and Euryops arabicus (Asteraceae). Also, the species of the genus Eryngiopus are categorized into two species groups, bakeri and gracilis, based on three and four pairs of prodorsal setae, respectively. A key to the world species of the genus Eryngiopus is provided too.

Introduction

The family Stigmaeidae (Acari: Trombidiformes: Prostigmata) contains 32 genera (Fan et al., 2016, Rehman et al., 2016) of which only five genera including Agistemus Summers, Cheylostigmaeus Willmann, Eustigmaeus Berlese, Eryngiopus Summers and Ledermuelleriopsis Willmann have been reported from Saudi Arabia so far (Alatawi, 2011a & b, Alatawi & Kamran, 2017).

The species of the genus Eryngiopus inhabit plant foliage, soil litter, lichens and mosses (Ueckermann & Meyer, 1987, Matioli et al., 2002). Members of this genus are considered as predators of soft-bodied insects and mite pests (Fan & Zhang, 2005, Khanjani et al., 2014) and known from different geographical regions of the world (Vacante & Gerson, 1988, Fan & Zhang, 2005).

Up to now, 31 valid species from the genus are known worldwide (Doğan et al., 2015, Fan et al., 2016). Previously, few regional keys have been made for the afrotropical species of the genus (Meyer, 1969, Ueckermann & Meyer, 1987, Van Dis & Ueckermann, 1993). A key to the all known Eryngiopus species was provided by Vacante & Gerson (1988).

The objectives of this study were to re-describe and illustrate E. discus Meyer, since the original description lacks complete details of the species (Meyer, 1969) which is the requirement of modern taxonomy, and to provide a key to the world species of Eryngiopus.

Materials and methods

Mite specimens were collected by shaking the plant foliage on a white paper with a fine tip camel hairbrush and preserved in 70% ethanol. Samples of soil and leaf debris were also collected from the field and were processed through Tullgren’s funnels. The preserved specimens were then mounted on glass slides in Hoyer’s medium under a stereomicroscope (SZX10, Olympus). The mounted specimens were dried in an oven at 40°C for one week. The specimens were identified under a phase contrast microscope (BX51, Olympus) with the help of literature and diagnostic keys. Different body parts were pictured using an Auto-Montage system (Syncroscopy, Cambridge) and illustrated with Adobe illustrator (Adobe Systems Incorporated). All measurements are given in micrometers (μm). Body width was measured at the broadest area and setae were measured from the setal base to the tip. Terminology and setal nomenclature follow those of Kethley (1990) and Grandjean (1944). All specimens have been deposited in the Acarology Research Laboratory, Department of Plant Protection, College of Food and Agriculture Science, King Saud University, Riyadh, Kingdom of Saudi Arabia.

Results and discussion
Family Stigmaeidae Oudemans
Genus: Eryngiopus Summers

Eryngiopus Summers, 1964: 186.

Type species: Eryngiopus gracilis Summers, 1964.

Diagnosis based on Fan & Zhang (2005).

In the present study, the species of genus Eryngiopus are categorized into two species groups based on the number of prodorsal setae (Table 1); 1) species group bakeri having three pairs of prodorsal setae (vi, ve and sci) including nine species reported from Turkey, Egypt, Yemen, Thailand, China, South Africa and USA; 2) species group gracilis having four pairs of prodorsal setae (vi, ve, sci and sce) comprising 22 species mostly reported from USA, New Zealand, Italy, South Africa, China, Russia, Uzbekistan, Iran, Pakistan and India (Doğan et al., 2015, Fan et al., 2016).

Table 1. Some morphological diagnostic characters of the species of the genus Eryngiopus.

Number of prodorsal setae, either 3 pairs (vi, ve, sci) or four pairs (vi, ve, sci, sce) (Table 1), is strong and constant morphological character to categorize the species of Eryngiopus into two species groups. Vacante & Gerson (1988) used number of prodorsal setae (three/four) pairs as an important and basic character to develop a key to 17 world species of Eryngiopus. Also, Van Dis & Ueckermann (1993) separated the Afrotropical Eryngiopus species and used number of prodorsal setae (three/four) pairs as the first couplet in the key.

Species group bakeri
Eryngiopus discus Meyer

Eryngiopus discus Meyer, 1969: 232.

Re-description of adult female (n= 8) (Figures 1-4)

Idiosoma oval — Length of body (excluding gnathosoma) 370 – 378; length of gnathosoma 75 – 80; width of idiosoma 170 – 175 at the level of setae c2.

Gnathosoma (Figures 1C, 3) — Chelicerae separated; palp five segmented; palptibial claw subequal to palptarsus; palptarsus with tridentate terminal eupathidion distally, one solenidion, one eupathidion and four simple setae; palptibia with one well developed claw and one seta-like accessory claw, and two simple setae; palpgenua with one serrate seta; palpfemur with one simple and 2 serrated setae. Subcapitulum with 2 pairs of subcapitular setae (m, n) and two pairs of adoral setae (or1, or2). Length of subcapitular setae as follows: m 55 – 57, n 29 – 31, or1 12 – 14, or2 14 – 17; distances: or1-or1 6 – 8, or2 -or2 10 – 12, or1-or2 5 – 7, m-m 25 – 27, n-n 30 – 32, or1-m 37 – 40, or2-n 40 – 44, or1-m 35 – 38, m-n 6 – 7.

Dorsum (Figures 1A, 2A-B) — Prodorsal shield divided medially by striations, bearing three pairs of setae (vi, ve, sci), setae sce absent, eyes present, 8 – 11 μm, post ocular bodies (pob) absent; hysterosomal striations with micro tubercles (Fig.1B), longitudinal between setae c1 and e1, and transverse posterior to e1. Setae f1 situated on small platelets. Suranal shield divided into three feebly developed plates bearing setae h1 and h2; setae h1 share larger median plate; setae h2 on smaller lateral plates. Hysterosoma bears eight pairs of setae. Dorsal idiosomal setae slender, slightly barbed and tapering towards end. Length of dorsal setae as follows: vi 20 – 23, ve 28 – 32, sci 18 – 21, c1 12 – 14, c2 23 – 25, d1 11 – 14, d2 12 – 14, e1 17 – 20, e2 14 – 17, f1 19 – 22, h1 27 – 31, h2 31 – 35. Distances between dorsal setae: vi-vi 25 – 27, ve-ve 48-53, vi-ve 19 – 21, sci-sci 77 – 83, ve-sci 31 – 34, c1-c1 62 – 66, c1-c2 68 – 71, c2-c2 124 – 127, c1-d1 73 – 75, d1-d1 93 – 97, d1-d2 41 – 43, d1-e1 44 – 48, d1-e2 26 – 30, d2-e2 50 – 55, d2-d2 133 – 138, e1-e1 41 – 44, e2-e2 51 – 55, e1-e2 45 – 48, e1-f1 35 – 38, f1-f1 76 – 81, f-h1 41 – 46, h1-h1 31 – 25, f1-h2 42 – 45, h2-h2 75 – 80, h1-h2 29 – 32; ratios: vi/vi-vi 0.76, c1/c1-c1 0.2, d1/d1-d1 0.12, e1/e1-e1 0.41, f1/f1-f1 0.26, h1/h1-h1 1.27, h2/h2-h2 1.10, h1/h2 0.88.

Figure 1. Eryngiopus discus Meyer, adult female: A – Dorsal view of idiosoma; B – Micro tubercles on dorsal striations; C – Ventral view of idiosoma.

Figure 2. Eryngiopus discus Meyer, adult female: A – Prodorsum; B – Opisthosoma; C – Genital region.

Figure 3. Eryngiopus discus Meyer, adult female: A – Palp; B – Palptibial claw & palptarsus (not scaled).

Venter (Figure 1C, 2C) — The first pair of intercoxal setae 1a ultra long and reaches to the bases of subcapitular setae m. The latter intercoxal setae 3a and 4a much shorter than first pair of intercoxals. Lengths of setae; 1a 80 – 86, 1b 16 – 18, 1c 13 – 14, 2c 15 – 17, 3a 21 – 23, 3b 20 – 22, 3c 17 – 20, 4a 20 – 23, 4b 17 – 20 and 4c 15 – 17, aggenital setae three pairs: ag1 16 – 17, ag2 23 – 25, ag3 19 – 20, ano-genital area with one genital setae, g and three pairs of pseudanal setae (ps1-3): g 16 – 18, ps1 19 – 22, ps2 23 – 25, ps 3 24 – 27. Distances between setae: 1a-1a 26 – 28, 3a-3a 56 – 58, 4a- 4a 35 – 37, ag1-ag1 26 – 28, ag2-ag2 38 – 40, ag3-ag3 49 – 52, ag1-ag2 20 – 21, ag2-ag3 20 – 21, ps1-ps1 32 – 34, ps2-ps2 35 – 38, ps3-ps3 20 – 21; g1-g1 6 – 7.

Legs (Figure 4) — Length of legs I-IV, (tarsal claws to coxal bases): 188-192, 154 – 159, 148 – 155, 153 – 159 respectively. Empodial shaft branches up into 2 pairs of tenent hairs before pass beyond tips of claws. Number of setae on leg segments as fellows: coxae 2-1-2-2; trochanters 1-1-1-1; femora 4-4-2-2; genua 3+1κ-1-0-0; tibiae 5+1φ-5+1φ-5+1φ-5+1φ; tarsi 13+1ω-9+1ω-7+1ω-7+1ω.

Figure 4. Eryngiopus discus Meyer, adult female: A – Leg I; B – Leg II; C – Leg III; D – Leg IV.

Male and immature stages — unknown

Material examined — Five females, Euryops arabicus (Asteraceae), Taif, 21.19385°N, 040.25704°E, October 11, 2016, coll. M. Ur Rehman, Muhammad Kamran; three females, foxtail grass Cenchrus sp. (Poaceae), Makkah to Taif road, Taif, 21.36528°N, 040.15897°E, 2015, coll. J.H. Mirza, M. Kamran.

Ecological note — The mite color was red-orange when collected. The species Eryngiopus discus was collected from foxtail grass Cenchrus sp. in association with date palm mite Oligonychus afrasiaticus (McGregor).

Key to the world species of the genus Eryngiopus SummersAfter Vacante & Gerson (1988)

Note — This key is based on the descriptions available in literature and few assumptions depending upon quality of illustrations.

1. Propodosoma with three pairs of setae (vi,ve, sci), prodorsal setae sce absent
...... species group bakeri ......... 2

— Propodosoma with four pairs of setae (vi, ve, sci, sce), prodorsal setae sce present
...... species group gracilis ........ 10

2. Aggenital setae two pairs
...... E. custodis van Dis & Ueckermann

— Aggenital setae three pairs
...... 3

3. Genu I with three setae
...... 4

— Genu I with four setae
...... 5

4. Tarsi II with 10 setae, ventral setae 3a long = 88
...... E. jiangxiensis Hu & Chen

— Tarsi II with 9 setae, ventral setae 3a short = 17
...... E. nanchangensis Hu & Chen

5. Femur I with five or six setae
...... 6

— Femur I with four setae
...... 7

6. Coxae IV with one seta, tarsi I with 14 setae
...... E. anatolicus Doğan, Dilkaraoğlu & Fan

— Coxae IV with two setae, tarsi I with 14 setae
...... E. yemenensis van Dis & Ueckermann

7. Suranal shield entire (undivided)
...... 8

— Suranal shield divided in to three feebly developed plates
...... 9

8. Ventral setae 1a very short (24), tarsi IV with seven setae
...... E. bakeri (McGregor)

— Ventral setae 1a ultra long (103), tarsi IV with eight setae
...... E. woodi Gomaa & El-Enany

9. Setae d1 less widely spaced d1¬-d1 = 80, dorsal striations simple, aggenital setae (ag2) shorter 14
...... E. yasumatsui Ehara & Wongsiri

— Setae d1 more widely spaced d1¬-d1 = 94-97, dorsal striations with micro tubercles, aggenital setae (ag2) longer 23
...... E. discus Meyer

10. Aggenital setae two pairs
...... 11

— Aggenital setae three pairs
...... 16

11. Genu I with three setae
...... E. bidens Meyer

— Genu I with four setae
...... 12

12. Genu II without setae, intercoxal setae 1a 70
...... 13

— Genu II with one setae, intercoxal setae 1a < 40
...... 14

13. Prodorsal shield entire, terminal sensillum on palptarsus forked
...... E. bifidus Wood

— Prodorsal shield divided, terminal sensillum on palptarsus simple
...... E. microsetus Summers

14. Prodorsal shield completely striated
...... E. parsimilis Ueckermann & Meyer

— Prodorsal shield divided medially
...... 15

15. Ventral setae 3a long = 42, terminal sensillum on palptarsus simple
...... E. arboreus Wood

— Ventral setae 3a short = 24, terminal sensillum on palptarsus forked
...... E. similis Wood

16. Femur I with 5 or 6 setae
...... 17

— Femur I with 3 or 4 setae
...... 20

17. Genu II with one seta, tarsi III and IV each with 8 setae
...... 18

— Genu II with 2 setae, tarsi III and IV each with 7 setae
...... E. nelsonensis Wood

18. Coxae I with one seta, femur III with 3 setae
...... E. vagantis Summers

— Coxae I with 2 setae, femur III with 2 setae
...... 19

19. Terminal sensillum on palptarsus simple, prodorsal shield divided medially
...... E. hamedanicus Khanjani, Mohammadi & Nazari

— Terminal palpal sensillum tridentate, prodorsal shield entire
...... E. affinis Barilo

20. Femur I with 3 setae
...... 21

— Femur I with 4 setae
...... 22

21. Genu setal formula 1-1-1-1, ratio vi/vi-vi = 0.18
...... E. coimbatorensis Gupta & David

— Genu setal formula 3-0-0-0, ratio vi/vi-vi = 1.3
...... E. langroudiensis Khanjani, Hazjizadeh & Ueckermann

22. Genu I with 3 setae
...... 23

— Genu I with 4 setae
...... 26

23. Coxae II with 2 setae
...... 24

— Coxae II with 1 seta
...... 25

24. Coxae IV with 2 setae, tarsi I with 11 setae
...... E. hortus (Chaudhri)

— Coxae IV with one seta, tarsi I with 14 setae
...... E. cirrus (Chaudhri)

25. Tarsi II with 9 setae, terminal palpal sensillum simple, first pair of intercoxal setae 1a large (>60)
...... E. audreae Maake, Ueckermann & Childers

— Tarsi II with 10 setae, terminal palpal sensillum forked, first pair of intercoxal setae 1a shorter
...... E. lindei Meyer

26. Trochanter IV with one seta
...... 27

— Trochanter IV without setae
...... 29

27. Coxae I with one seta, prodorsal shield divided medially
...... E. tauricus Kuznetsov

— Coxae I with 2 setae, prodorsal shield entire
...... 28

28. Tibia IV with 4 setae, tarsi III and IV with 7 setae
...... E. gracilis Summers

— Tibia IV with 6 setae, tarsi III and IV with 8 setae
...... E. summersi Vacante & Gerson

29. Genu II with one seta
...... E. dicrotrichus Fan, Zhang & Liu

— Genu II without setae
...... 30

30. Suranal shield bearing two pairs of setae (h1, h2), propodosomal striations divergent beyond shields
...... E. placidus Kuznetsov

— Suranal shield with one pair of setae (h1), Propodosomal striations convergent beyond shields
...... E. siculus Vacante & Gerson

Acknowledgement
The authors wish to thank the Deanship of Scientific Research at King Saud University, Riyadh for providing facilities and fund to complete this research work through the research project [RG-1438-055]. We are also grateful to Dr. Carlos H.W. Flechtmann (University of Sao Paulo, Departamento de Entolomogia e Acarologia, Brazil) and Dr. Pholoshi A. Maake (Plant Protection Research Institute, Queenswood, South Africa) for providing literature.
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Date received:
2017-11-27
Date accepted:
2018-03-12
Date published:
2018-06-01

Edited by:
Faraji, Farid

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2018 Rehman, Muneeb Ur; Kamran, Muhammad and Alatawi, Fahad J.
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