Joharchi, Omid ¹ ; Döker, Ismail ² and Khaustov, Vladimir A. ³

¹✉ Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Semakova Str.10, 625003 Tyumen, Russia & Agriculture Science and Technology Institute, Andong National University, Andong, Republic of Korea.
²Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Semakova Str.10, 625003 Tyumen, Russia & Cukurova University, Agricultural Faculty, Department of Plant Protection, Acarology Laboratory, 01330, Adana, Türkiye.
³Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Semakova Str.10, 625003 Tyumen, Russia.

2023 - Volume: 63 Issue: 4 pages: 1139-1153

ZooBank LSID: E22C69A6-5A6A-4811-A85E-D3FAAD4316E5

Original research

Keywords

Abstract

Introduction

Mesostigmata is a large, cosmopolitan order of mites found in soil, litter, rotting wood, compost, dung, carrion, nests, house dust, and similar detritus-based niches. They also live in association with plants and fungi (Lindquist et al. 2009). The mite family Ascidae includes 17 genera and just over 370 described species in two subfamilies, Ascinae and Arctoseiinae (Moraes et al. 2016; Lindquist and Moraza 2018; Santos and Moraes 2016; Kazemi 2019; Joharchi et al. 2021). Within the subfamily Ascinae, Leioseius is considered a group of predatory mites of small arthropods or nematodes based on their cheliceral morphology (Lindquist and Moraza 2018). The genus includes 23 nominal species that occur in either soil and litter habitats or marine debris and niches throughout most of the world, with the exception of high alpine and polar regions (Lindquist and Moraza 2018; Santos and Moraes 2016; Kazemi 2019; Joharchi et al. 2021). Prior to the present study, only four species of Leioseius were reported from Russia (Lindquist and Moraza 2018; Marchenko 2012, 2017; Joharchi et al. 2021). During a study of edaphic predatory mites of Russia, a new species of Leioseius was collected from lichen-covered soil in the subarctic zone of northern Tyumen, western Siberia. The new species is described and illustrated on the basis of morphological characters of adult females and males. We also present the first record of L. changbaiensis Yin & Bei, 1991 from Russia with additional morphological information and new illustrations based on specimens collected in the Altai Republic near the type locality. This species, known only from the type series, was found under bark in China (Changbai Mountains, Jilin Province). In addition, an identification key for all known Russian species of the genus is presented.

Material and methods

Samples were collected over a four-year period (2019-2022) in different regions of Russia in search of edaphic predatory mites. Mites were extracted from soil and decayed tree stump using the Berlese-Tullgren funnels, then cleared in lactic acid solution and mounted in Hoyer's medium (Walter and Krantz 2009). The examinations of the specimens were performed with Zeiss Axio Imager A2 compound microscope equipped with differential interference contrast optical systems, attached to camera AxioCam ICc 5. Most images were captured in stacks (with focal depth manually controlled). Selected images were combined using Helicon Focus 7.6.4 Pro (Helicon Soft Ltd., 2000). Digital drawings were prepared using Adobe Photoshop CS2 software based on the original pencil line drawings. Images and morphological measurements were taken via ZEN 2012 software (version 8.0). Photomicrographs were taken with an AxioCam 506 camera (Carl Zeiss, Germany). Measurements of structures are expressed as ranges (minimum–maximum) in micrometers (μm). The length and width of the dorsal shield were taken from the anterior to the posterior margins along the midline, and at the level of s3 respectively. Length and width of the sternal shield were measured at the maximum length and broadest points (at level between coxae II and III) respectively. The length of the epigynal shield was measured along the midline from the anterior margin of the hyaline extension to the posterior margin of the shield, and its width where maximal, posterior to epigynal setae st5. Ventrianal shield was measured along the midline from the anterior to posterior margins, including the cribrum; its width was measured at the broadest point. The length of the second cheliceral segment was measured from its base to the apex of the fixed digit, and that of the movable digit from the base to the apex. Leg length was measured from the base of the coxa to the apex of the tarsus (excluding the pre-tarsus). The notation for idiosomal setae follows Lindquist and Evans (1965) modified slightly by Lindquist (1994), and for leg and palp setae follows that of Evans (1963, 1964), and other anatomical structures mostly follow Evans and Till (1979). Distinction of pore-like structures on the idiosomatic integument as either poroids/lyrifissures or gland pores follows mostly that of Athias-Henriot (1971, 1975), with small additions for gland pores gvb1, gvb2 (Makarova et al. 2021). Notation for pore-like structures of the peritrematal region follows that of Lindquist and Moraza (2018). The holotype and paratypes are deposited at the Acarological Collection of the Tyumen State University Museum of Zoology, Tyumen, Russia (TUMZ).

Taxonomy

Family Ascidae Oudemans

Genus Leioseius Berlese

Lasioseius (Leioseius) Berlese, 1916: 45.

Type species: Ameroseius minusculus Berlese, 1905, by original designation.

Diagnosis

The concept of Leioseius used here is based on that of Moraes et al. (2016) and Lindquist and Moraza (2018) with modifications by Kazemi et al. (2019).

Leioseius changbaiensis Yin & Bei, 1991

Leioseius changbaiensis Yin & Bei, 1991: 147.

Leioseius changbaiensis. Lindquist & Moraza 2018: 1988.

(Figures 1–3)

Specimens examined — Two females, Ulaganskiy Rayon, Altai Republic, Russia, 50°24′23.4″N 87°35′58.8″E, 19 July 2021, alt. 1827 m, O. Joharchi, I. Döker, V.A. Khaustov coll., under bark of rotten stump.

Remarks — Leioseius changbaiensis was originally described from Changbai Mountains, Jilin Province, China (Yin and Bei 1991). This species, known only from the type series, was found under the bark of a tree, and is now recorded in the Altai Republic, Russia, very close to type locality in China from the same habitat. Our female specimens (Figure 1) agree well with the original description given by Yin and Bei (1991). We were unable to locate the types of L. changbaiensis but the following ecological, geographic and morphological features suggests that the specimens which we examined are conspecific with those described by Yin and Bei (1991): (1) habitat-specific, found under the bark of tree; (2) distributed in Northeast Asia (China and Altai Republic); (3) morphological features. However, the original description is brief and its illustrations are incomplete, lacking most important details, especially those concerning leg chaetotaxy. We herein provide additional morphological characters to complement the previous description (Yin and Bei 1991) of L. changbaiensis based on specimens from Russia, but also in comparison with the original description.

Dorsal idiosoma — (Figures 1A & 2A) — Dorsal shield strongly reticulated over entire surface, somewhat scabrid, with short lateral incisions between setae s6 and S1, setae s2 on shield's anterolateral margins (Figures 1A & 2A), with 33 pairs of setae, including 18 pairs on podonotal region (j1–6, z1–6, s1–6), including s2 on its anterolateral margins and 15 pairs on opisthonotal region, all marginal r-R-setae on soft cuticle, setae all of similar short, smooth, except clunal setae (Z5) thicker, hardly ciliated and slightly longer than adjacent setae (Figures 1A, 2A & 2C). Lateral soft cuticle with about 12 of setae, r2–5 and R1–6, two or three submarginal UR's posterolaterally and a pair of poroids (idRp) (Figures 1A & 2A).

Ventral idiosoma — (Figures 1B, 2B, 2D, 2E & 2G) — Presternal region with a pair of smooth platelets which bear setae st1 (Figures 1A, 2B & 2D). Epigynal shield somewhat vase form, anterior margin of shield convex, not overlapping posterior area of sternal shield, posterior margin truncate, protruding at level setae st5, paragenital poroids on soft cuticle beside posterolateral margins of epigynal shield (Figures 1B, 2B & 2G). Peritrematal shields anteriorly united with dorsal shield at anterior level of setae z1, and posteriorly united with parapodal strips behind coxae IV and exopodal fragments alongside coxae II-IV; shields bearing five pairs of discernible pore-like structures: two pairs of gland pores and three pairs of poroids, gv2 on soft cuticle behind coxae IV (Figures 1B & 2B). Opisthogaster with nine pairs of setae in addition to circumanal setae [not seven pairs which has been shown in the original description, see Yin and Bei 1991; this aspect was viewed as an exception to the diagnosis concept of the Leioseius genus by Moraes et al. (2016: 26)], ventrianal shield with three pairs of opisthogastric setae (excluding circumanals), Zv2, Zv3, Jv5 on adjacent soft cuticle (Figures 1B, 2B & 2E). Spermathecal system not discernible.

Gnathosoma — (Figures 1C–E, 5F, 2H & 2I). Subcapitulum with seven rows of deutosternal denticles, each similarly narrow, with five to ten denticles (Figures 1C & 2F); subcapitular setae h1 and h3 similar in length, clearly longer than capitular setae pc, and h2 setae (Figure 1C & 2F). Epistome trifid, with denticulate apices (Figures 1D & 2H). Fixed digit with tiny offset subapical tooth, short pilus dentilis and row of four or five well-spaced teeth; movable digit bidentate (Figures 1E & 2I).

Legs — (Figure 3). Legs II (Figure 3B) and III (Figure 3C) short, legs I (Figure 3A) longer than legs IV (Figure 3D), and shorter than dorsal shield. Complement of setae on leg segments for coxae I-II-III-IV: 2, 2, 2, 1; for trochanters: 6, 5, 5, 5; for femora: 12, 11, 6, 6; chaetotactic formulae for genua I-IV, respectively: (2-3/2, 3/1-2) (2-3/1, 2/1-2) (2-2/1, 2/1-1) (2-2/1, 3/0-1); tibiae: (2-3/2, 3/1-2) (2-2/1, 2/1-2) (2-1/1, 2/1-1) (2-1/1, 3/1-2); genu I and tibia I with av-2 (Figure 3A), genu IV with nine setae, pd3 present (Figure 3D); tibia III with al-2, without pl-2 (Figure 3C). Tarsi II–IV with 18 setae, all setae on tarsi II–IV similar in form and moderate length to most other tarsal setae; not differentiated in curved whip-like form, setae (v-1) and (v-2) similar in form and moderate length to most other tarsal setae; (d-2) not differentiated in curved whip-like form; (d-1) less than half as long as pretarsus to bases of claws; shape of setae on leg segments as Figures 3A–D.

Leioseius subarcticus Joharchi n. sp.

ZOOBANK: 9B264648-6944-43BC-9F71-57EB992FE9CC

(Figures 4–7)

Type material

Holotype, female, Yamalo-Nenets Autonomous Okrug, Purovsky District, Russia, 65°05′17.5″N 78°10′59.6″E, 17 July 2022, A.A. Khaustov coll., from the soil covered with lichens. Paratypes, ten females and three males, same data as holotype.

Diagnosis (adult)

Dorsal shield tuberculate-reticulate over nearly entire surface, with well-formed lateral incisions between setae s6 and S1; shield with 33 pairs of smooth setae, except Z5, J4, J5 with a few barbs, clunal setae (Z5) longest. Epistome trifid, with denticulate apices. Postanal seta on ventrianal shield with a few barbs. Leg I tibia and genu each with 13 setae (av2 present); leg III genu with eight setae, pv absent; all setae on tarsi II–IV similar in form and moderate length to most other tarsal setae; not differentiated in curved whip-like form. Female: presternal area comprises with a few transverse curved lines anteriorly and a pair of sclerotized smooth platelets posteriorly which bear setae st1. Ventrianal shield with three pairs of opisthogastric setae (Jv2–4) (excluding circumanals). Fixed digit with row of four or five well-spaced teeth; movable digit bidentate. Male: ventrianal shield with seven pairs of opisthogastric setae (excluding circumanals), setae Zv3 off shield; postgenital groove with strip of four platelets, as in female. Spermatodactyl apex narrowed and strongly incurved.

Description (adult female)

(Figures 4–5 & 7A–H)

Six specimens measured.

Dorsal idiosoma — (Figures 4A, 7A & 7C) — Dorsal idiosoma 370–402 long, 210–220 wide (at level of r3), dorsal shield 370–402 long, 183–193 wide, tuberculated in reticulate pattern over nearly entire surface (Figures 4A & 7A), with lateral incisions between setae s6 and S1, barely reaching to transverse level of Z1. Shield with 33 pairs of setae, including 18 pairs on podonotal region (j1–6, z1–6, s1–6), including s2 on its anterolateral margins and 15 pairs on opisthonotal region, all marginal r-R-setae on soft cuticle, setae generally similar in short (15–22), smooth, pointed form; setae J1–4 similar in short length to J5(14–17), about half as long as longitudinal intervals between their bases; Z5, J4, J5 with a few barbs (Figure 7C), clunal setae (Z5) longest (30–33). Shield with complement of 23 pairs of discernible pore-like structures, including seven pairs of gland openings (gd1–2, gd4–6, and gd8–9) and 16 poroids (id1, id2, id4–id5, idm1–idm5, idx, and idl1–idl5) (Figures 4A & 7A), gland pores gd8 and gd9 conspicuously enlarged (Figure 7C). Lateral soft cuticle with about 12 of setae, r2–5 and R1–6, two or three submarginal UR's posterolaterally and a pair of poroids (idRp). Muscle-marks (sigillae) as illustrated and showed in Figures 4A & 7A.

Ventral idiosoma — (Figures 4B, 7B, 7D & 7J) — Tritosternum with paired pilose laciniae (47–52), fused basally (6–9), columnar base 18–21 × 9–12 wide; presternal area comprises with a few transverse curved lines anteriorly and a pair of sclerotized smooth platelets posteriorly which bear setae st1 (16–20). Sternal shield length 88–95, narrowest between coxae II (50–60), widest (85–90); bearing two pairs of smooth and subequal in length setae (17–20) (st2, st3), two pairs of lyrifissures (iv1, iv2) and one pair of sub-oval poroids on posterolateral corners of shield margin (iv3), endopodals between coxae I-II fused with sternal shield, shield reticulated over entire surface, gland pores gvb1, gvb2 and gv1 not discernible (Figures 4B & 7B). Setae st4 (15–18) on soft cuticle. Endopodal strips narrow between coxae III and IV. Epigynal shield reticulated/lineated, its rounded hyaline anterior margin not overlapping posterior area of sternal shield, its lateral margins slightly concave, narrowed anterior to setae st5 (18–21), and its posterior margin slightly convex, with corners rounded at the level st5; shield 75–90 long, 28–32 at narrowest width between legs IV, 50–58 at widest level posteriorly. Paragenital poroids (iv5) located on soft cuticle beside posterolateral margins of shield (near seta st5), postgenital groove with strip of four platelets. Ventrianal shield inversely subtriangular, anterior margin of shield somewhat flat and slightly convex lateral margins tapered posteriorly, shield length 115–125, width 130–150 at Jv3 level (broadest point) and width 94–100 at Jv5 level; shield reticulated over most of surface, lines punctate posteriorly, with three pairs of opisthogastric setae (Jv2–4) (16–22) (excluding circumanals), and one pair of gland pores (gv3), plus para-anal (16–19) and postanal (25–30) setae, postanal seta with a few barbs (Figures 4B, 7B & 7D). Opisthogastric soft cuticle with six pairs of opisthogastric setae flanking ventrianal shield, Jv1, Zv1, Zv2 (14–22) anteriorly and Zv3, Zv4 (17–20), Jv5 (24–27) laterally; two pairs of well-spaced metapodal platelets [elongate lateral pair 22–25 long, 6–8 wide, small inner pair dimensions 7–10 by 3–5], and six pairs of poroids (including ivp) (Figures 4B, 7B & 7D). Peritremes long, extending to level of paravertical setae (z1). Peritrematal shields anteriorly united with dorsal shield at anterior level of setae z1, and posteriorly united with parapodal strips behind coxae IV and exopodal fragments alongside coxae II-IV; shields bearing five pairs of discernible pore-like structures: two pairs of gland pores and three pairs of poroids, gv2 on soft cuticle behind coxae IV (Figures 4B & 7B).

Spermathecal system (Figure 7J): sperm access system consists of unsclerotized structures, leading by way of a long, uniformly narrow tubulus from an infundibulum on either side at the inner bases of legs III–V to a single, more visually evident, oval receptaculum, from which a more conspicuous duct leads to rather circular sacculus.

Gnathosoma — (Figures 4C–E & 7E–H). Epistome anterior margin triramous, with denticulate apices (Figures 4D & 7G). Hypostomal groove with seven transverse rows of denticles, each row with 2–8 denticles, with smooth anterior and posterior transverse lines (Figures 4C & 7F), subcapitular setae h1 and h3 similar in length (18–22), clearly longer than capitular setae pc (14–17), and h2 (10–13) (Figures 4C & 7F). Corniculi subparallel, robust and horn-like, with bluntly pointed tips, shorter than internal malae. Supralabral process not distinguishable. Internal malae with one pair of fimbriate projections (Figures 4C & 7F); labrum markedly longer than internal malae with pilose surface. Palptarsal claw two-tined, all setae on palps smooth and needle-like except setae al and d3 on femur, al1–2 on genu somewhat spine-like; palptarsus without long setae (Figure 7E). Second segment of chelicera (including the fixed digit) 85–90 long, fixed digit of chelicera with tiny offset subapical tooth, short pilus dentilis and row of four or five well-spaced teeth, dorsal cheliceral seta matchstick-shape, arthrodial membrane with a rounded flap and some filaments, cheliceral lyrifissures distinct; movable digit of chelicera (32–36) bidentate (Figures 4E and 7H).

Legs — (Figure 5). Legs II (Figure 5B) (215–225) and III (Figure 5C) (185–205) short, legs I (Figure 5A) (270–285) longer than legs IV (Figure 5D) (255–270), and shorter than dorsal shield. Complement of setae on leg segments for coxae I-II-III-IV: 2, 2, 2, 1; for trochanters: 6, 5, 5, 5; for femora: 12, 11, 6, 6; chaetotactic formulae for genua I-IV, respectively: (2-3/2, 3/1-2) (2-3/1, 2/1-2) (2-2/1, 2/1-1) (2-2/1, 3/0-1); tibiae: (2-3/2, 3/1-2) (2-2/1, 2/1-2) (2-1/1, 2/1-1) (2-1/1, 3/1-2); genu I and tibia I with av-2 (Figure 5A), genu IV with nine setae, pd3 present (Figure 5D); tibia III with al-2, without pl-2 (Figure 5C). Tarsi II–IV with 18 setae, all setae on tarsi II–IV similar in form and moderate length to most other tarsal setae; not differentiated in curved whip-like form, setae (v-1) and (v-2) similar in form and moderate length to most other tarsal setae; (d-2) not differentiated in curved whip-like form; (d-1) less than half as long as pretarsus to bases of claws; shape of setae on leg segments as Figures 5A–D.

Description (adult male)

(Figures 6 & 7I)

Three specimens measured.

Dorsal idiosoma — Dorsal shield 320–335 long, 160–170 wide; shield ornamentation, complement of pore-like structures and setation as in female.

Ventral idiosoma — (Figures 6A) — Tritosternum formed as in female, with paired pilose laciniae (47–52), fused basally (6–8), columnar base 12–14 × 8–10 wide. Presternal region with a pair of distinct platelets flanking genital opening. Sternitigenital shield length 140–145, narrowest between coxae IV (25–30), widest at level between coxae II-III (77–83); posterior margin width 32–36; shield reticulated over nearly entire surface, free from endopodal strips beside coxae III–IV; setae st1, st2 similar in lengths (18–20), st3–st5 slightly shorter (10–13). Poroids iv5 on soft cuticle behind posterolateral corners of sternitigenital shield (Figure 6A). Postgenital groove with strip of four platelets, as in female. Ventrianal shield reticulated over most of surface, with lines punctate posteriorly, anterior margin flat, and posterolateral margins gradually tapered; shield wider (163–12) than long (123–12), with seven pairs of opisthogastric setae, Zv3 (10–12) off shield; JV1 and ZV1(11–13), JV2, JV3, ZV2 (14–17), JV4 (11–13), JV5 (20–23); postanal seta (24–27) with a few barbs and about 1.5 as long as paranal setae (13–16). Peritremes, peritrematal shield and exopodal fragments as in female.

Gnathosoma — (Figures 6B & 7I) — Fixed digit with offset subapical tooth, pilus dentilis and row of about five teeth similar as in female; movable digit (22–25) unidentate; spermatodactyl (24–27) apex narrowed and strongly incurved (Figures 6B & 7I). Form and length of other gnathosomatic structures as in female.

Legs — Legs similar to those of female, without dimorphism in thickness or spine-like setal modifications. Lengths I 251–255, II 195–205, III 150–160, IV 207–215.

Immature stages — Unknown.

Etymology

The specific name is derived from the name of the region (subarctic zone) in which the type locality occurs.

Remarks

According to Lindquist and Moraza (2018) and the identification key to Leioseius species provided in this publication, L. subarcticus Joharchi most resembles Leioseius tuberculatus Lindquist & Moraza, 2018 (couplet 19 in the identification key), but L. subarcticus can easily be distinguished from this species by having a pair of platelets bearing setae st1 in presternal region, while platelets absent in L. tuberculatus; leg I tibia and genu each with 13 setae (av2 present), while in L. tuberculatus tibia and genu of leg I each with 12 setae, av2 absent; postanal seta on ventrianal shield with a few barbs, while completely smooth in L. tuberculatus; ventrianal shield of male with seven pairs of opisthogastric setae (setae Zv3 off shield), while in L. tuberculatus ventrianal shield of male with eight pairs of opisthogastric setae including Zv3. The following key is based on direct examination of all species.

Key to species of Leioseius occurring in the Russia, partly from Lindquist and Moraza 2018

1. Ventrianal shield with two pairs of opisthogastric setae
...... 2

— Ventrianal shield with three or four pairs of opisthogastric setae
...... 3

2. Lateral incisions of dorsal shield shallow, not reaching transverse level of setae Z1; ventrianal shield with opisthogastric setae Jv2, Jv3 (Jv4 and Jv5 off shield, on soft cuticle), clunal setae Z5 not elongated, less than twice as long as other Z-series setae
...... L. minusculus (Berlese, 1905)

— Lateral incisions of dorsal shield twice as deep as level to setae Z1; ventrianal shield with opisthogastric setae Jv3, Jv5 (Jv2 and Jv4 on soft cuticle close to anterior margin of shield), dorsal shield with elongated clunal setae Z5, at least twice as long as other Z-series setae
...... L. mirabilis Nikolsky, 1981

3. Ventrianal shield with four pairs of opisthogastric setae
...... L. naglitschi Karg, 1965

— Ventrianal shield with three pairs of opisthogastric setae
...... 4

4. Ventrianal shield subtrapezoidal, its lateral margins not bearing setae Jv4 but diverging posteriorly to bear setae Jv5
...... L. elongatus Evans, 1958

— Ventrianal shield inversely subtriangular to subcircular, with lateral margins rounded to bear setae Jv4; setae Jv5 on soft cuticle close to posterolateral corners of ventrianal shield
...... 5

5. Dorsal shield strongly reticulated over entire surface, somewhat scabrid (Figures 1A & 2A), clunal setae Z5 thicker and hardly ciliated (Figures 1A & 2C), postanal seta of ventrianal shield smooth (Figures 1B, 2E)
...... L. changbaiensis Yin & Bei, 1991

— Dorsal shield tuberculate-reticulate over nearly entire surface (Figure 7A), postanal and clunal (Z5) setae with a few barbs (Figures 4B & 7D)
...... L. subarcticus Joharchi n. sp.

Acknowledgements

The present research was supported by the grant from the Russian Science Foundation, project number 20–64–47015. We cordially thank Dr. Alexander Khaustov and Mr. Roman Latyntsev (Tyumen State University, Russia) for their help in collecting samples, and in logistics, respectively.

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