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Three new species and new records of Pediculaster (Acari: Pygmephoridae) from Western Siberia, Russia

Khaustov, Alexander A.1

1✉ Tyumen State University, Tyumen, Russia.

2020 - Volume: 60 Issue: 2 pages: 317-337

DOI: 10.24349/acarologia/20204370
ZooBank LSID: D86736C3-28A9-427D-B243-41BF5C93465A

Original research

Keywords

Pygmephoroidea systematics, morphology female dimorphism larva fauna

Abstract

Three new species of Pediculaster: P. tjumeniensis sp. nov., P. bisetus sp. nov., and P. rarus sp. nov. are described from rotting wood in Western Siberia. P. tjumeniensis is described based on phoretic and non-phoretic females and larva; P. bisetus and P. rarus are described based on phoretic females only. Pediculaster camerikae Khaustov, 2008, P. montanus Khaustov, 2008, and P. dudinskyi Khaustov, 2011 are recorded for the first time from Asia, the latter species is also recorded for the first time from Russia. Unusual character states of P. tjumeniensis larva are discussed.


Introduction

The genus Pediculaster Vitzthum, 1931 (Acari: Pygmephoroidea) is one of the largest in the family Pygmephoridae and comprises more than 100 described species in the world fauna (Khaustov et al. 2014; Khaustov 2015). Pediculaster-mites are fungivorous and inhabit a great variety of habitats, e.g. soil, litter, mosses, dung, nest material, decaying organic material (Camerik and Kheradmand 2010). Several species are considered as pests of mushrooms in commercial mushroom-houses (Cross and Kaliszewski 1988). Mites of the genus Pediculaster are characterized by the presence of two morphologically different forms of females: non-phoretic or ''normal'' and phoretic (Camerik et al. 2006; Martin 1978). Most Pediculaster species are phoretic on various Diptera, especially associated with cattle dung (Camerik 2010). Little is known about Pediculaster mites inhabiting rotting wood and forest litter. Only few species were described from rotting wood: P. fusarii (Smiley and Moser, 1976) collected from the galleries of bark beetles from USA (Smiley and Moser 1976), P. dudinskyi Khaustov, 2011 collected from a tree hole from Ukraine (Khaustov 2011), P. ermilovi Khaustov, 2015 and P. lignarius Khaustov, 2015 collected from rotting wood in Western Siberia (Khaustov 2015). Khaustov (2015) reviewed mites of the genus Pediculaster of Russia and provided the key to phoretic females of Palaearctic species. Only two species, P. ermilovi and P. lignarius have been described and recorded from Western Siberia so far.

During the study of heterostigmatic mites of Western Siberia, three new species of Pediculaster were found in the samples of rotting wood. Moreover, three species, P. dudinskyi Khaustov, 2011, P. camerikae Khaustov, 2008b, and P. montanus Khaustov, 2008b were recorded from the Asia for the first time.

Materials and methods

Mites were collected from samples taken from decaying trees and cow dung, using Berlese funnels. They were posteriorly cleared in lactic acid and mounted in Hoyer's medium. The terminology for the idiosoma and legs follows that of Lindquist (1986); the nomenclature of subcapitular setae and the designation of cheliceral setae follow those of Grandjean (1944, 1947), respectively. The systematics of Pygmephoroidea follows that of Khaustov (2004, 2008a). All measurements are given in micrometers (μm) for the holotype and paratypes (in parentheses). For leg chaetotaxy, the number of solenidia is given in parentheses. Mite morphology was studied using a Carl Zeiss AxioImager A2 compound microscope with phase contrast and DIC illumination. Photomicrographs were taken with Hitachi KP-HD20A digital camera.

Abbreviations: ap1-ap5 apodemes 1-5, appr prosternal apodeme, appo poststernal apodeme, apsej sejugal apodeme, Tr trochanter, Fe femur, Ge genu, Ti tibia, Ta tarsus, TiTa tibiotarsus, ass accessory setigenous structure, sol solenidion, ags anterior genital sclerite, pgs posterior genital sclerite, mgs median genital sclerite, php 1-3 pharyngeal pumps 1-3.

Systematics

Family Pygmephoridae Cross, 1965

Genus Pediculaster Vitzthum, 1931

Type species: Pygmephorus mesembrinae Canestrini, 1881, by original designation.

Pediculaster tjumeniensis sp. nov.

ZOOBANK: 9C126801-3491-4277-8757-9C9AE42FB5BD

(Figs 1–9A)

Description

Phoretic female (Figs 1–3, 9A) — Length of idiosoma 265 (200–305), width 140 (105–160).

Figure 1. Pediculaster tjumeniensis sp. nov., phoretic female: A – dorsum of the body, B – venter of the body. Legs omitted.

Gnathosoma (Figs 1, 9A) – Length of gnathosomal capsule 26 (23–27), width 29 (28–32). Dorsal median apodeme weakly developed. All gnathosomal setae pointed; setae cha, chb and dFe with few very small barbs, other gnathosomal setae smooth. Palp tibiotarsus with well-developed blunt-tipped claw and tiny eupathid-like seta; palps ventrally with well-developed solenidion and mushroom-shaped accessory setigenous structure. Php 1 small, bow-shaped, located inside gnathosomal capsule; php 2 and 3 oval (Fig. 9A), situated close to each other on long oesophagus and far separated from php 1. Lengths of gnathosomal setae: cha 10 (8–12), chb 14 (10–15), dFe 13 (9–13), dGe 18 (12–18), m 16 (11–16).

Idiosomal dorsum (Fig. 1A) – All dorsal shields with numerous small round dimples. Stigmata small, oval, one-chambered and associated with long tracheal trunks. All dorsal setae blunt-ended and barbed; trichobothria sc1 short, spherical. Cupules ia on tergite D and ih on tergite H very small, round. Lengths of dorsal setae: v1 29 (22–29), v2 30 (25–32), sc2 57 (43–58), c1 40 (29–40), c2 48 (35–52), d 43 (32–45), e 24 (17–24), f 45 (30–45), h1 37 (27–38), h2 14 (10–16). Distances between setae: v1v1 10 (10–12), v2v2 31 (26–32), sc2sc2 46 (41–53), c1c1 44 (33–49), c1c2 30 (21–34), dd 73 (52–78), ef 21 (15–23), ff 45 (32–51), h1h1 51 (34–52), h1h2 18 (14–19).

Idiosomal venter (Fig. 1B) – Ventral plates with numerous small round dimples. Setae 1b and 2a pointed; other ventral setae blunt-ended; setae ps1 and ps3 smooth, over ventral setae weakly barbed; setae 2a much longer than other ventral setae; in one specimen left seta 2c abnormally long and pointed. Ap1, ap2 and apsej well developed and joined with appr; ap3 and ap4 well developed and joined with appo; ap5 weaker sclerotized than other apodemes and joined with appo. Posterior margin of poststernal plate evenly rounded, without median lobe. Anterior and posterior genital sclerites long and narrow; median genital sclerite small, oval. Lengths of ventral setae: 1a 19 (15–19), 1b 26 (18–29), 1c 17 (14–17), 2a 43 (38–48), 2b 18 (4–19), 2c 16/20 (14–17), 3a 18 (14–20), 3b 16 (13–17), 3c 19 (14–21), 4a 16 (12–17), 4b 19 (15–22), 4c 18 (13–20), ps1 8 (5–8), ps2 26 (17–27), ps3 7 (4–9).

Figure 2. Pediculaster tjumeniensis sp. nov., phoretic female: A – left leg I, dorsal aspect, B – left leg II, dorsal aspect.

Legs (Figs 2, 3) – Leg I (Fig. 2A). Leg setation: Tr 1 (v'), Fe 4 (d, l', l'', v''), Ge 4 (l', l'', v', v''), TiTa 17(4) (d, l', l'', v', v'', k, pl', pl'', p', p'', tc', tc'', ft', ft'', s, pv', pv'', ω1, ω2, φ1, φ2). Tibiotarsus slightly thickened, distinctly wider than genu. Lengths of solenidia ω1 14 (11–14), ω2 11 (9–11), φ1 9 (7–9), φ2 9 (8–10); solenidion φ1 slightly clavate, other solenidia finger-shaped. Setae (p), (tc) and (ft) eupathid-like; seta d of femur smooth, spatulate distally; seta k of tibiotarsus smooth and weakly blunt-ended; setae l' of femur and (l) of genu blunt-ended and barbed; other leg setae (except eupathidia) pointed and barbed. Leg II (Fig. 2B). Leg setation: Tr 1 (v'), Fe 3 (d, l', v''), Ge 3 (l', l'', v'), Ti 4(1) (d, l', v', v'', φ), Ta 6(1) (pl'', tc', tc'', pv', pv'', u', ω). Solenidia ω 9 (7–9) and φ 5 (4–5) finger-shaped. Tarsal claws with thickened basal half; empodium long and narrow, with widened tip. All leg setae barbed; setae d, l' of femur and u' of tarsus blunt-ended, other leg setae pointed. Leg III (Fig. 3A). Leg setation: Tr 1 (v'), F2 3 (d, v'), Ge 2 (l', v'), Ti 4(1) (d, l', v', v'', φ), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws and empodium as on tarsus II. Solenidion φ 4 (3–4) weakly clavate. All leg setae barbed; setae d, v' of femur and l' of genu blunt-ended, other leg setae pointed. Leg IV (Fig. 3B). Leg setation: Tr 1 (v'), Fe 2 (d, v'), Ge 1 (v'), Ti 4(1) (d, l', v', v'', φ), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws simple, hooked, empodium narrower than on tarsi II and III. Solenidion φ 3 (2–3) rod-like. All leg setae barbed; seta v' of femur blunt-ended, other leg setae pointed.

Figure 3. Pediculaster tjumeniensis sp. nov., phoretic female: A – left leg III, dorsal aspect, B – left leg IV, dorsal aspect.

Non-phoretic female (Figs 4–6) — Length of idiosoma 240–300, width 125–150.

Figure 4. Pediculaster tjumeniensis sp. nov., non-phoretic female: A – dorsum of the body, B – venter of the body. Legs omitted.

Gnathosoma (Fig. 4) – Length of gnathosomal capsule 27–31, width 33–38. Gnathosoma and pharyngeal pumps in general as in phoretic female, but cheliceral setae and seta dFe smooth. Lengths of gnathosomal setae: cha 9–11, chb 14–15, dFe 13–14, dGe 15–16, m 17–19.

Idiosomal dorsum (Fig. 4A) – as in phoretic female, but dorsal sclerites weaker sclerotized and dimples smaller, difficult to discern. Lengths of dorsal setae: v1 19–23, v2 19–24, sc2 37–44, c1 26–31, c2 39–44, d 28–36, e 15–20, f 27–39, h1 23–33, h2 6–8. Distances between setae: v1v1 11–12, v2v2 28–32, sc2sc2 29–33, c1c1 40–45, c1c2 25–34, dd 61–70, ef 16–18, ff 42–45, h1h1 45–49, h1h2 14–15.

Idiosomal venter (Fig. 4B) – similar to that of phoretic female, but plates weaker sclerotized and dimples smaller; setae 2a normally not very long and blunt-ended, and only in one specimen left seta 2a long and pointed and similar to that of phoretic female. Apsej indistinct; ap5 stronger sclerotized than in phoretic female. Lengths of ventral setae: 1a 13–15, 1b 13–18, 1c 11–15, 2a 14–33, 2b 12–16, 2c 10–13, 3a 14–18, 3b 13–17, 3c 14–18, 4a 12–15, 4b 13–18, 4c 14–15, ps1 6, ps2 17–22, ps3 4–5.

Figure 5. Pediculaster tjumeniensis sp. nov., non-phoretic female: A – left leg I, dorsal aspect, B – left leg II, dorsal aspect.

Legs (Figs 5, 6) – Leg I (Fig. 5A). Tibia and tarsus separated. Tarsal claw simple, hooked. Leg setation: Tr 1 (v'), Fe 4 (d, l', l'', v''), Ge 4 (l', l'', v', v''), Ti (6)(2) (d, l', l'', v', v'', k, φ1, φ2),\down Ta 13(2) (pl', pl'', p', p'', tc', tc'', ft', ft'', s, pv', pv'', u', u'', ω1, ω2). Lengths of solenidia ω1 16–19, ω2 13–15, φ1 6–8, φ2 10–11; solenidion φ1 clavate, other solenidia finger-shaped. Setae (p), (tc) and (ft) eupathid-like; seta k of tibiotarsus smooth and weakly blunt-ended; other leg setae (except eupathidia) pointed and barbed. Leg II (Fig. 5B). Leg setation: Tr 1 (v'), Fe 3 (d, l', v''), Ge 3 (l', l'', v'), Ti 4(1) (d, l', v', v'', φ), Ta 7(1) (pl'', tc', tc'', pv', pv'', u', u'', ω). Solenidia ω 11–12 and φ 8–9 finger-shaped. Tarsal claws simple, hooked; empodium short and wide. All leg setae barbed; seta l' of femur blunt-ended, other leg setae pointed. Leg III (Fig. 6A). Leg setation: Tr 1 (v'), Fe 2 (d, v'), Ge 2 (l', v'), Ti 4(1) (d, l', v', v'', φ), Ta 7 (pl'', tc', tc'', pv', pv'', u', u''). Claws and empodium as on tarsus II. Solenidion φ 6–7 finger-shaped. All leg setae barbed; seta v' of femur blunt-ended, other leg setae pointed. Leg IV (Fig. 6B). Leg setation: Tr 1 (v'), Fe 2 (d, v'), Ge 1 (v'), Ti 4(1) (d, l', v', v'', φ), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws and empodium as on tarsi II and III. Solenidion φ 3–4 rod-like. All leg setae barbed; seta v' of femur blunt-ended, other leg setae pointed.

Figure 6. Pediculaster tjumeniensis sp. nov., non-phoretic female: A – left leg III, dorsal aspect, B – left leg IV, dorsal aspect.

Larva (Figs 7, 8) — Length of idiosoma 195–215, width 105–115.

Figure 7. Pediculaster tjumeniensis sp. nov., larva: A – dorsum of the body, B – venter of the body. Legs omitted.

Gnathosoma (Figs 7, 8) – Length of gnathosomal capsule 27–30, width 31–34. Cheliceral setae cha short and thick, other gnathosomal setae smooth and pointed; setae chb absent. Dorsal median apodeme absent. Accessory setigenous structure distinctly shorter than palpal solenidion. Subcapitulum with two pairs of setae (m, n). Lengths of gnathosomal setae: cha 3–4, dFe 9–10, dGe 12–14, m 14–15, n 10–11. Pharyngeal pumps 2 and 3 as in female, php 1 small, bow-shaped and situated on the short distance from php 2 inside propodosoma.

Idiosomal dorsum (Fig. 7A) – Prodorsum with one trapezium-shaped shield with four pairs of setae; tergite C divided into three plates, one median with one pair of setae c1 and two laterals with setae c2; tergites D, EF and H with same number of setae as in females. All dorsal setae strongly barbed; setae h1 and h2 pointed, other dorsal setae blunt-ended. Tergites D and H with small round cupules ia and ih, respectively. All dorsal shields with small round dimples. Lengths of dorsal setae: v1 14–18, v2 12–16, sc1 21–29, sc2 30–35, c1 23–26, c2 25–31, d 25–33, e 18–23, f 29–35, h1 28–35, h2 59–63. Distances between setae: v1v1 9–11, v2v2 41–45, sc1sc1 28–29, sc2sc2 49–53, c1c1 40–42, dd 43, ef 11–12, ff 33–34, h1h1 12–14, h1h2 10–11.

Idiosomal venter (Fig. 7B) – Coxal fields I-III separated medially and with two pairs of setae each. Ap1, ap2 and ap3 well developed; other apodemes absent. All ventral setae barbed; setae ps1-3 pointed, other ventral setae blunt-ended. Lengths of ventral setae: 1a 11–13, 1b 11–13, 2a 12–13, 2b 12–14, 3a 15–20, 3b 12–16, ps1 14–16, ps2 17–20, ps3 18–20.

Figure 8. Pediculaster tjumeniensis sp. nov., larva: A – left leg I, dorsal aspect, B – left leg II, dorsal aspect, C – left leg III, dorsal aspect.

Legs (Fig. 8) – Leg I (Fig. 8A). Tarsus with two simple hooked claws; empodium absent. Leg setation: Tr 0, Fe 4 (d, l', l'', v''), Ge 4 (l', l'', v', v''), Ti (6)(1) (d, l', l'', v', v'', k, φ1),\down Ta 11(1) (pl', pl'', tc', tc'', ft', ft'', s, pv', pv'', u', u'', ω1). Lengths of solenidia ω1 10–14, φ1 7–9; solenidion ω1 finger-shaped; solenidion φ1 clavate. Setae (tc) eupathid-like; seta k of tibiotarsus smooth and weakly blunt-ended; setae l' of femur and v' of genu blunt-ended and barbed, other leg setae (except eupathidia) pointed and barbed. Leg II (Fig. 8B). Leg setation: Tr 0, Fe 3 (d, l', v''), Ge 3 (l', l'', v'), Ti 4(1) (d, l', v', v'', φ), Ta 7(1) (pl'', tc', tc'', pv', pv'', u', u'', ω). Solenidia ω 8–10 and φ 4–5 finger-shaped. Tarsal claws simple, hooked; empodium short and wide. Seta l' of femur smooth and blunt-ended; seta v' of genu barbed and blunt-ended, other leg setae pointed and barbed. Leg III (Fig. 8C). Leg setation: Tr 0), F2 3 (d, v'), Ge 2 (l', v'), Ti 4 (d, l', v', v''), Ta 7 (pl'', tc', tc'', pv', pv'', u', u''). Claws and empodium as on tarsus II. Solenidion φ absent. Seta pl'' of tarsus spine-shaped, smooth; setae d, v' of femur and l' of genu blunt-ended and barbed, other leg setae pointed and barbed. Femur not divided into basi- and telofemur.

Figure 9. DIC micrographs of pharyngeal pumps II and III of phoretic females: A – Pediculaster tjumeniensis sp. nov.,, B – Pediculaster bisetus sp. nov.

Male unknown.

Type material — Phoretic female holotype slide ZISP T-Pygm-004: Russia, Tyumen Province, Tyumen, ''Zatyumenskiy park'', 57°09' N, 65°26' E, in the rotting log of birch, 21 April 2019, A.A. Khaustov leg. Paratypes: 7 phoretic females, same data as holotype; 4 phoretic and 4 non-phoretic females, same locality and collector, 10 July 2019; 2 phoretic females and 7 larvae, same locality and collector, 26 April 2019.

Type deposition — The holotype and 4 phoretic females paratypes are deposited in the collection of the Zoological Institute of RAS, Saint Petersburg, Russia; other paratypes are deposited in the mite collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.

Etymology — The name of the new species refers to its distribution in Tyumen city, the capital of Tyumen Province, Russia.

Differential diagnosis — Phoretic female of the new species is most similar to P. sellnickianus (Rack, 1964) and P. limosinae Samsinak, 1984 (not separable morphologically from P. sellnickianus) by the presence of three pairs of setae on coxal fields I and II, setae ps2 longer than ps3, and setae 2a much longer than 2b. The new species can be distinguished from P. sellnickianus by having setae c2 clearly longer than c1 (setae c1 and c2 subequal in P. sellnickianus), by the presence of ap5 (ap5 absent in P. sellnickianus), and setae e no more than twice longer than h2 (setae e more than 3 times longer than h2 in P. sellnickianus). Non-phoretic female of the new species is most similar to P. permagnus (Rack, 1971) but can be distinguished from it by longer distance between setae e and f, which less than 3 times shorter than distance f-f (e-f about 4 times shorter than f-f in P. permagnus), by solenidion φ2 distinctly longer than φ1 (solenidia φ2 and φ1 subequal in P. permagnus), and by much longer solenidion ω2, which reaching far beyond the base of solenidion ω1 (solenidion ω2, much shorter and not reaching base of solenidion ω1 in P. permagnus). Larva of the new species can be distinguished from all described larvae of Pediculaster by the presence of setae n on subcapitulum (setae n absent in all described larvae of Pediculaster).

Pediculaster bisetus sp. nov.

ZOOBANK: 4AAFFE22-DC6F-40FD-B423-D666234F4DD3

(Figs 9B–12)

Description

Phoretic female (Figs 9B–12) — Length of idiosoma 210 (210–240), width 96 (105–115).

Figure 10. Pediculaster bisetus sp. nov., phoretic female: A – dorsum of the body, B – venter of the body. Legs omitted.

Gnathosoma (Figs 9B, 10) – Length of gnathosomal capsule 20 (20–21), width 21 (22–24). Dorsal median apodeme weakly developed. All gnathosomal setae smooth; setae cha and chb blunt-ended, other gnathosomal setae pointed. Palp tibiotarsus with well-developed blunt-tipped claw and tiny eupathid-like seta; palps ventrally with well-developed solenidion and mushroom-shaped accessory setigenous structure. Php 1 small, bow-shaped, located inside gnathosomal capsule; php 2 oval, php 3 with lateral ''wings'' (Fig. 9B), both pumps situated close to each other on long oesophagus and far separated from php 1. Lengths of gnathosomal setae: cha 6 (6), chb 8 (7–8), dFe 6 (6–8), dGe 7 (7–10), m 12 (12–13).

Idiosomal dorsum (Fig. 10A) – All dorsal shields with numerous small round dimples. Stigmata small, oval, one-chambered and associated with long tracheal trunks. Setae e and h2 smooth, other dorsal setae barbed; setae h2 pointed, other dorsal setae blunt-ended; trichobothria sc1 short, spherical. Cupules ia on tergite D and ih on tergite H very small, round. Lengths of dorsal setae: v1 22 (21–23), v2 21 (18–21), sc2 36 (36–40), c1 24 (24–29), c2 31 (31–39), d 29 (29–36), e 8 (8–13), f 31 (31–38), h1 29 (29–34), h2 5 (5–7). Distances between setae: v1v1 8 (7–9), v2v2 22 (21–22), sc2sc2 31 (31–34), c1c1 33 (33–39), c1c2 20 (20–23), dd 49 (49–61), ef 6 (5–7), ff 49 (49–59), h1h1 44 (44–53), h1h2 5 (5–8).

Idiosomal venter (Fig. 10B) – Ventral plates with numerous small round dimples. Setae 1b pointed, other ventral setae blunt-ended; setae ps2 barbed, over ventral setae smooth. Setae 2b on coxal fields II absent. Ap1, ap2 and apsej well developed and joined with appr; ap3 and ap4 well developed and joined with appo; ap5 weaker sclerotized than other apodemes and joined with appo. Posterior margin of poststernal plate with weak median lobe. Anterior and posterior genital sclerites long and narrow; median genital sclerite small, oval. Lengths of ventral setae: 1a 10 (9–11), 1b 13 (13–14), 1c 9 (9), 2a 10 (10–12), 2c 7 (6–8), 3a 10 (10–12), 3b 10 (10–11), 3c 12 (12), 4a 9 (9–10), 4b 12 (11–14), 4c 10 (10–12), ps1 4 (4–5), ps2 16 (14–16), ps3 3 (3).

Figure 11. Pediculaster bisetus sp. nov., phoretic female: A – right leg I, dorsal aspect, B – right leg II, dorsal aspect.

Legs (Figs 11, 12) – Leg I (Fig. 11A). Leg setation: Tr 1 (v'), Fe 4 (d, l', l'', v''), Ge 4 (l', l'', v', v''), TiTa 17(4) (d, l', l'', v', v'', k, pl', pl'', p', p'', tc', tc'', ft', ft'', s, pv', pv'', ω1, ω2, φ1, φ2). Tibiotarsus cylindrical, as wide as genu. Lengths of solenidia ω1 8 (8–9), ω2 4 (4), φ1 7 (7), φ2 4 (4–5); all solenidia clavate. Setae (p), (tc) and (ft) eupathid-like; seta d of femur smooth, spatulate distally; seta pl' of tibiotarsus smooth and pointed; setae v' of trochanter and k of tibiotarsus smooth or with one barb and blunt-ended; setae l' of femur and (l) of genu blunt-ended and barbed; other leg setae (except eupathidia) pointed and barbed. Leg II (Fig. 11B). Leg setation: Tr 1 (v'), Fe 3 (d, l', v''), Ge 3 (l', l'', v'), Ti 4 (d, l', v', v''), Ta 6(1) (pl'', tc', tc'', pv', pv'', u', ω). Solenidion ω 5 (5) clavate, solenidion φ absent, but pore-like structure situated on its typical insertion point. Tarsal claws with thickened basal half; empodium long and narrow, with widened tip. Setae v' of trochanter and l' of femur smooth and blunt-ended; setae d of femur and u' of tarsus blunt-ended and barbed, other leg setae pointed. Leg III (Fig. 12A). Leg setation: Tr 1 (v'), F2 3 (d, v'), Ge 2 (l', v'), Ti 4 (d, l', v', v''), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws and empodium as on tarsus II. Solenidion φ absent, but pore-like structure situated on its typical insertion point. All leg setae barbed; setae v' of trochanter, d, v' of femur and u' of tarsus blunt-ended, other leg setae pointed. Leg IV (Fig. 12B). Leg setation: Tr 0, Fe 2 (d, v'), Ge 1 (v'), Ti 4 (d, l', v', v''), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws simple, hooked, empodium as on tarsi II and III. Solenidion φ absent, but pore-like structure situated on its typical insertion point. All leg setae barbed; setae d and v' of femur blunt-ended, other leg setae pointed.

Figure 12. Pediculaster bisetus sp. nov., phoretic female: A – right leg III, dorsal aspect, B – right leg IV, dorsal aspect.

Non-phoretic female, male and larva unknown.

Type material — Phoretic female holotype slide ZISP T-Pygm-005: Russia, Tyumen Province, Tyumen, ''Zatyumenskiy park'', 57°09' N, 65°26' E, in the rotting log of birch, 29 September 2019, A.A. Khaustov leg. Paratypes: 11 phoretic females, same data as holotype.

Type deposition — The holotype and 2 phoretic female paratypes are deposited in the collection of the Zoological Institute of RAS, Saint Petersburg, Russia; other paratypes are deposited in the mite collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.

Etymology — The name of the new species is a combination of two Latin words bi meaning two and seta meaning bristle and refers to presence of two pairs of setae on coxal fields II.

Differential diagnosis — The new species is most similar to P. athiasae (Wicht, 1970) by the presence of three pairs of setae on coxal fields I, two pairs of setae on coxal fields II, subequal setae v1 and v2 and well-developed ap5. The new species can be distinguished from the latter in having one-chambered stigmata (two-chambered in P. athiasae), by smooth setae e (setae e barbed in P. athiasae), by the absence of seta on trochanter IV (trochanter IV with seta in P. athiasae), and distinctly shorter dorsal body setae (dorsal body setae distinctly longer in P. athiasae).

Pediculaster rarus sp. nov.

ZOOBANK: B3B6E53C-F601-46F5-A384-38011767AB4F

(Figs 13–15)

Description

Phoretic female (Figs 13–15) — Length of idiosoma 280, width 130.

Figure 13. Pediculaster rarus sp. nov., phoretic female: A – dorsum of the body, B – venter of the body. Legs omitted.

Gnathosoma (Fig. 13) – Length of gnathosomal capsule 25, width 29. Dorsal median apodeme well developed. All gnathosomal setae smooth; setae cha blunt-ended, other gnathosomal setae pointed. Palp tibiotarsus with well-developed blunt-tipped claw and tiny eupathid-like seta; palps ventrally with well-developed solenidion and mushroom-shaped accessory setigenous structure. Php 1 small, bow-shaped, located distinctly outside gnathosomal capsule; php 2 and php 3 oval, situated close to each other on long oesophagus and far separated from php 1. Lengths of gnathosomal setae: cha 7, chb 11, dFe 8, dGe 15, m 17.

Idiosomal dorsum (Fig. 13A) – All dorsal shields with numerous small round dimples. Stigmata small, oval, one-chambered and associated with long tracheal trunks. All dorsal setae blunt-ended; setae h2 smooth, other dorsal setae barbed; trichobothria sc1 short, spherical. Cupules ia on tergite D and ih on tergite H very small, round. Tergites C, D, and EF with porous areas as illustrated. Lengths of dorsal setae: v1 25, v2 24, sc2 46, c1 32, c2 39, d 35, e 22, f 38, h1 36, h2 6. Distances between setae: v1v1 11, v2v2 26, sc2sc2 35, c1c1 36, c1c2 25, dd 50, ef 14, ff 43, h1h1 37, h1h2 13.

Idiosomal venter (Fig. 13B) – Ventral plates with numerous small round dimples. Setae 1b, 1c, 2b, 3c, 4b, and 4c pointed, other ventral setae blunt-ended; setae ps2 barbed, other ventral setae smooth; setae 2b much longer than other ventral setae; setae ps2 situated distinctly anteriad ps1. Ap1, ap2 and apsej well developed and joined with appr; ap3 and ap4 well developed and joined with appo; ap5 weaker sclerotized than other apodemes and joined with appo. Posterior margin of poststernal plate evenly rounded, without median lobe. Anterior and posterior genital sclerites long and narrow; median genital sclerite indistinct. Lengths of ventral setae: 1a 10, 1b 14, 1c 12, 2a 12, 2b 73, 2c 13, 3a 16, 3b 13, 3c 20, 4a 12, 4b 21, 4c 19, ps1 7, ps2 7, ps3 27.

Figure 14. Pediculaster rarus sp. nov., phoretic female: A – left leg I, dorsal aspect, B – left leg II, dorsal aspect.

Legs (Figs 14, 15) – Leg I (Fig. 14A). Leg setation: Tr 1 (v'), Fe 4 (d, l', l'', v''), Ge 4 (l', l'', v', v''), TiTa 17(4) (d, l', l'', v', v'', k, pl', pl'', p', p'', tc', tc'', ft', ft'', s, pv', pv'', ω1, ω2, φ1, φ2). Tibiotarsus cylindrical, slightly wider than genu. Lengths of solenidia ω1 21, ω2 11, φ1 7, φ2 6; solenidion φ1 clavate, other solenidia finger-shaped. Setae (p), (tc) and (ft) eupathid-like; eupathidium p'' very short (Fig. 14A´); seta d of femur smooth, spatulate distally; setae v' of trochanter and pl' of tibiotarsus smooth and pointed; seta k of tibiotarsus smooth and weakly blunt-ended; other leg setae (except eupathidia) pointed and barbed. Leg II (Fig. 11B). Leg setation: Tr 1 (v'), Fe 3 (d, l', v''), Ge 3 (l', l'', v'), Ti 4(1) (d, l', v', v'', φ), Ta 6(1) (pl'', tc', tc'', pv', pv'', u', ω). Solenidion ω 10 finger-shaped, solenidion φ 3 weakly clavate, situated in depression. Tarsal claws with thickened basal half; empodium long and narrow, with widened tip. Setae v' of trochanter and tc'' of tarsus smooth and pointed; setae u' of tarsus blunt-ended and barbed, other leg setae pointed and barbed. Leg III (Fig. 15A). Leg setation: Tr 1 (v'), Fe 2 (d, v'), Ge 2 (l', v'), Ti 4(1) (d, l', v', v'', φ), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws and empodium as on tarsus II. Solenidion φ 3 weakly clavate, situated in depression. Seta tc'' of tarsus smooth and pointed; setae v' of femur and u' of tarsus blunt-ended and barbed, other leg setae pointed and barbed. Leg IV (Fig. 15B). Leg setation: Tr 1 (v'), Fe 2 (d, v'), Ge 1 (v'), Ti 4 (d, l', v', v''), Ta 6 (pl'', tc', tc'', pv', pv'', u'). Claws simple, hooked, empodium as on tarsi II and III. Solenidion φ absent, but pore-like structure situated on its typical insertion point. All leg setae pointed and barbed.

Figure 15. Pediculaster rarus sp. nov., phoretic female: A – left leg III, dorsal aspect, B – left leg IV, dorsal aspect.

Non-phoretic female, male and larva unknown.

Type material — Phoretic female holotype slide ZISP T-Pygm-006: Russia, Tyumen Province, Tyumen district, vicinity of lake Kuchak, 57°21'N, 66°03'E, in rotting stamp, 26 September 2018, A.A. Khaustov leg.

Type deposition — The holotype is deposited in the collection of the Zoological Institute of RAS, Saint Petersburg, Russia.

Etymology — The name of the new species is derived from Latin rarus meaning rare and refers to its rareness.

Remark — The new species is described based on single specimen. However, it is in good condition and very well differs from closely related species. All attempts to collect additional specimens were unsuccessful.

Differential diagnosis — The new species is most similar to P. chistyakovi Khaustov and Ermilov, 2008 by the presence of three pairs of setae on coxal fields I and II, setae ps3 distinctly longer than ps2, setae v1 and v2 subequal, and setae 2b much longer than 2a. The new species can be distinguished from the latter in having setae sc2, c2, f, and h1 blunt-ended (setae sc2, c2, f, and h1 pointed in P. chistyakovi), by setae ps2 situated distinctly anteriad ps1 (setae ps2 and ps1 situated on the same level in P. chistyakovi), by much shorter setae d on femur and tibia IV which not exceed beyond tip of tarsus (setae d on femur and tibia IV very long and exceed beyond tip of tarsus in P. chistyakovi), and by the presence of ap5 (ap5 absent in P. chistyakovi).

Pediculaster dudinskyi Khaustov, 2011

Pediculaster dudinskyi Khaustov, 2011, 265, Figs 1–5.

Phoretic female of this species was described from a tree hole of poplar in Western Ukraine (Khaustov 2011).

This is the first record of P. dudinskyi from Asia and Russia.

Material examined — One phoretic female, Russia, Tyumen Province, Tyumen, ''Zatyumenskiy park'', 57°09' N, 65°26' E, in the rotting log of birch, 26 April 2019, A.A. Khaustov leg.

Pediculaster camerikae Khaustov, 2008

Pediculaster camerikae Khaustov, 2008b, 166, Figs 25–29.

Phoretic female of this species was described from the cow dung in Crimea (Khaustov 2008b).

This is the first record of P. camerikae from Asia.

Material examined — Four phoretic females, Russia, Kurgan prov., Zverinogolovskiy distr., vicinity of settl. Ukrainets, 54°24ʹN 64°49ʹE, in cow dung, 20.09.2019, A.A. Khaustov leg.

Pediculaster montanus Khaustov, 2008

Pediculaster montanus Khaustov, 2008b, 162, Figs 13–24.

Phoretic female and male of this species were described from the cow dung in Crimea (Khaustov 2008b).

This is the first record of P. montanus from Asia.

Material examined — 30 phoretic females, 2 males, Russia, Kurgan prov., Zverinogolovskiy distr., vicinity of settl. Ukrainets, 54°24ʹN 64°49ʹE, in cow dung, 20.09.2019, A.A. Khaustov leg.

Discussion

Larval stage is currently described only for five species of Pediculaster: P. fusarii (Smiley and Moser, 1976), P. mesembrinae (Canestrini, 1881), P. morelliae Rack, 1974, P. permagnus (Rack, 1971), and P. pseudomanicatus Camerik, 2001 (Smiley and Moser 1978; Martin 1978; Camerik 2001; Camerik et al. 2006). All described larvae are very similar morphologically and differ mainly by the lengths of setae and number of cheliceral setae (setae chb present or absent). The description of larva in P. tjumeniensis sp. nov. revealed several unusual characters. The most remarkable is the presence of two pairs of subcapitular setae (setae n present). The presence of subcapitular setae n is unknown in all described pygmephoroid mites, including available descriptions of larval stages. Occasionally, the abnormal seta n was recorded in adult female of scutacarid mite Pygmodispus latisternus Paoli (Khaustov 2008a). In larva of P. tjumeniensis sp. nov. subcapitular setae n present in all seven studied larvae and undoubtedly is not abnormal. The presence of this plesiomorphic character is most likely a result of an evolutionary reversion rather than retention. Other unusual characters found in P. tjumeniensis sp. nov. larvae are the absence of the solenidion on tibia III and spiniform seta pl'' on tarsus III. These characters could be used in the future not only for separation of species but probably also for creating of species-groups or subgenera in the genus Pediculaster.

Acknowledgements

The author thanks to Mr. Latyntsev R.V. (Tyumen State University, Russia) for the help in logistics.

References

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Date received:
2020-02-04
Date accepted:
2020-04-09
Date published:
2020-04-16

Edited by:
Baumann, Julia

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2020 Khaustov, Alexander A.

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