1✉ Odessa I. I. Mechnikov National University, Odessa, Ukraine & Ukrainian I. I. Mechnikov Anti-Plague Research Institute, Odessa, Ukraine.
2Institute of Systematics and Ecology of Animals, Novosibirsk, Russia.
3Institute of Environmental and Agricultural Biology (X-BIO), Tyumen State University, Tyumen, Russia.
2019 - Volume: 59 Issue: 4 pages: 531-541https://doi.org/10.24349/acarologia/20194353
Like other nest-making animals (e.g. birds, rodents, scarab beetles, wasps, ants and termites), bees, including bumblebees, are hosts to a wide diversity of gamasid mites (Eickwort, 1994). Members of the genera Parasitellus Willmann, 1939 (Parasitidae), Pneumolaelaps Berlese, 1920 (Laelapidae) and some species of Proctolaelaps Berlese, 1923 (Melicharidae) have a more intimate association with bumblebees (Westerboer, 1963; Bregetova, 1977b; Hyatt, 1980; Joharchi et al., 2019). The fauna of bumblebee-associated gamasid mites in North Asia has been well studied before (Davydova, 1976; Davydova and Bogdanov, 1976; Davydova and Nikolsky, 1986; Davydova, 1988; Davydova and Bogatyrev, 1990; Klimov, 1998; Joharchi et al., 2019). During a survey of bumblebee-associated gamasid mites in Western Siberia (Tyumen Region) Proctolaelaps sibiriensis (Davydova, 1988) was collected, a species known only from the type series. The aim of this article is to redescribe the female of P. sibiriensis based on type series and new material because the original description of this species is brief and both the description and illustrations lack many important details. Moreover, we provide a world key to bumblebee-associated species of the genus Proctolaelaps.
Bumblebees were collected with a sweep net from flowers and placed individually in vials of 70% ethanol. Thereafter, alcohol sediments from the vials were inspected for phoretic mites with the aid of the stereomicroscope Discovery V8 (Carl Zeiss). Specimens were cleared in lactic acid solution and mounted in Hoyer's medium (Walter and Krantz, 2009). The morphology of mites was studied with the aid of an Axioskop 40 microscope (Carl Zeiss), and Axio Imager A2 microscope (Carl Zeiss) with DIC and phase-contrast objectives. Photomicrographs were taken with a M3CMOS 10000 camera (Sigeta).
The morphological terminology generally follows Evans and Till (1979). Dorsal and ventral setae were labelled according to the systems of Lindquist and Evans (1965), and Lindquist (1994). Palpal and leg chaetotaxy follows Evans (1963a, b). The notation for idiosomal pore-like structures follows Johnston and Moraza (1991). Lengths of shields were measured from the anterior to posterior shield margins along the midline. The length of the second cheliceral segment was measured from their base to the apex of the fixed digit. The length of legs was taken from the base of the coxa to the apex of the tarsus, excluding the ambulacrum. The measurements are given in micrometers (μm).
Proctolaelaps sibiriensis is redescribed based on type series (Novosibirsk Province) and specimens collected in Tyumen Province. The studied material is deposited in Zoological Museum of Institute of Systematics and Ecology of Animals (Novosibirsk, Russia) (type series of P. sibiriensis), the Zoological Museum of Tyumen State University (Tyumen, Russia), and the Department of Zoology of Odessa I. I. Mechnikov National University (Odessa, Ukraine).
Type species: Proctolaelaps productus Berlese, 1923, by monotypy.
Diagnosis — the diagnosis of Proctolaelaps used here is based on that of Moraes et al. (2016).
(Figs 1–4, 5A, B)
Material examined — Holotype female, Russia, Novosibirsk, arboretum, 55°05ʹN, 82°51ʹE, from nest of Bombus hypnorum, 1984, N.R. Bogatyrev coll.; two females, same data; four females, same geographical data, from nest of Bombus agrorum, 22 July 1985, N.R. Bogatyrev coll.; three females, same geographical data, from nest of Bombus hypnorum, 10 and 16 July 1987, N.R. Bogatyrev coll.; two females, Russia, Tyumen Province, Nizhnetavdinsky Region, vicinity of lake Kuchak, 57°21ʹN, 66°03ʹE, from Bombus sp., 27 April 2018, O. Joharchi coll.
Diagnosis — Dorsal shield with complex volumetric shape, harshly sclerotized with distinct reticulate ornamentation over whole surface except more poorly sclerotized regions in anterior extension and posterior; with 43 pairs of setae; dorsal setae simple, needle-like, except spindle-like setae j1 and serrated setae Z5. Pre-sternal area transversely lineate, without platelets. Sternal shield completely reticulated except posteriorly where overlapped by hyaline flap of epigynal shield, with group of small rounded cells in centre of shield. Poroids iv3 absent. Anterior membranous margin of epigynal shield subtriangular, elongate; posterior margin of shield slightly rounded; shield reticulated. Three pairs of postgenital platelets present. Anal shield subquadrate; reticulated; anus small, located in centre of shield. Soft opisthogastric cuticle with 11 pairs of setae. Epistome subtriangular with small blunt process distally and undulated laterally. Deutosternum with seven rows of denticles, rows 1–6 connected, 7th row free; rows with two lateral and 1–2 medial denticles. Corniculi with paraxial process. Fixed cheliceral digit with apical hook, two teeth on cutting surface and one small tooth on median line; subapical tooth with well-expressed membranous lobe instead of pilus dentilis. Movable digit with apical hook and one small tooth on cutting surface. Leg chaetotaxy formulae normal for genus, including tibia III with 9 setae; most leg setae thickened and born on small tubercles.
Idiosomal dorsum (Figs 1, 5A) —Dorsal shield ovoid; 367–425 long and 275–300 maximum width at R1 level; shield completely covers dorsum; shield strongly sclerotized and reticulate except lateral to J1– J3 and posterior; cells transversally elongated near lateral margin, with a median ridge consisting of oval and rectangular reticulations; dorsum with 43 pairs of setae (j1–j6, z1–z6, s1–s6, r2–r6, J1– J5, Z1– Z5, S1– S5, R1– R5; base of setae R5 visible ventrally) and 24 pairs of distinguishable pore-like structures (seven gland pores and 17 poroids). All dorsal setae simple, needle-like, except spindle-like setae j1 and serrated setae Z5; lengths of setae: j1 10–17, j2 45–51, j3 40–50, j4 47–57, j5 51–63, j6 45–55, z1 18–21, z2 36–45, z3 38–50, z4 39–50, z5 46–56, z6 24–30, s1 25–31, s2 30–37, s3 35–41, s4 37–47, s5 26–36, s6 24–30, r2 25–28, r3 30–36, r4 29–37, r5 35–40, r6 28–40, J1 35–45, J2 33–42, J3 27–39, J4 10–20, J5 12–17, Z1 15–25, Z2 15–25, Z3 15–25, Z4 9–17, Z5 15–25, S1 18–30, S2 18–25, S3 13–17, S4 10–15, S5 9–15, R1 24–33, R2 22–27, R3 20–25, R4 17–25, R5 8–10.
Idiosomal venter (Figs 2, 5B) — Tritosternum with trapezoidal base, 11–13 long, 11–13 wide at base, laciniae pilose, fused for about fifth of total length 9–10, free parts 34–44 long. Pre-sternal area transversely lineate, without platelets. Sternal shield fused with endopodal elements of coxae I/II and coxae II/III; 57–65 long along midline, 94–125 wide at level of endopodal projections between coxae I/II, 135–160 wide at level of endopodal projections between coxae II/III, 76–95 wide at narrowest part between coxae II; with three pairs of setae (st1–st3) and two pairs of poroids (iv1, iv2); poroids iv1 positioned posteriad of seta st1, poroids iv2 positioned between setae st2 and st3; posterior margin weakly concave, arched to level of bases of setae st3; reticulated except posteriorly where overlapped by hyaline flap of epigynal shield, with group of small rounded cells in centre of shield. Setae st4 located on small metasternal platelets; poroids iv3 absent. Anterior membranous margin of epigynal shield subtriangular, overlapping posterior margin of sternal shield, extending to level of setae st2, posterior margin of shield slightly rounded; epigynal shield reticulated; epigynal shield 142–146 long with hyaline membrane, 100–105 without membrane, with greatest width of hyaline flap 93–95, greatest width of posterior part 72–85; poroids iv5 on soft cuticle, closely associated with shield. Three pairs of postgenital platelets present. Free endopodal plates between coxae III and IV. Anal shield subquadrate; reticulated; 95–100 long and 89–95 wide; anus small, located in centre of shield, anal opening 17–19 long; cribrum wide, reaching posterolateral corners of shield; one pair of gland pores (gv3) close to shield margin, at level of paranal setae. Posterior to coxae IV, two pairs of elongate metapodal platelets present; largest platelet 21–33 long, 5–9 wide; smaller platelet 4–6 long, 2–3 wide. Opisthogastric cuticle with 11 pairs of setae ( JV1– JV5, ZV1– ZV5, UR) and three pairs of small poroids. Exopodal platelets fused, curved posteriorly around coxa IV , bearing gland pores gv2 at posterior extremity. Peritrematal shields fused with dorsal shield at level of setae s1; with four pairs of distinguishable pore-like structures (poroids ip2, ip3 and gland pores gp2, gp3); peritreme extending forward to level of j2. All ventral setae simple, needle-like; setae JV5 and post-anal seta stout; lengths of setae: st1 38–43, st2 27–33, st3 21–28, st4 22–33, st5 19–25, JV1 15–20, JV2 16–20, JV3 14–17, JV4 12–13, JV5 16–22, ZV1 15–18, ZV2 13–17, ZV3 11–15, ZV4 9–13, ZV5 9–13, UR 9–13, para-anal setae 10–13, post-anal seta 19–23. Spermathecal apparatus not distinguishable.
Gnathosoma (Fig. 3) — Epistome subtriangular with small blunt process distally and undulated laterally (see Fig. 3A). Subcapitulum 65–72 wide at widest level. Deutosternum with seven rows of denticles, rows 1 to 6 connected by lateral margins, and row 7 free; rows with two lateral and 1–2 medial denticles (Fig. 3B). Hypostome with 4 pairs of simple setae; palpcoxal seta (pc) 18–25, hp1 15–20, hp2 12–15, hp3 24–26. Corniculi 20–25 long, 5–6 wide, horn-like, sclerotized, with small paraxial processes; internal malae slender, extending to paraxial processes of corniculi; salivary styli with blunt apices, reaching tips of corniculi. Palp length from trochanter to apex of tarsus 75–83; palpfemoral seta al, palpgenual setae al1 and al2 spatulate, other setae simple, palptarsal apotele 2-tined. Fixed cheliceral digit with short dorsal projection (dorsal mucro) over base; with apical hook, two teeth on cutting surface and one small tooth on median line (presumably for gripping hairs of bumblebee); subapical tooth with well-expressed membranous lobe instead of pilus dentilis, protrudes freely above the top of fixed digit or leans towards the movable digit of chelicera (at pressure on the slide as in Fig. 3c); dorsal and antiaxial lyrifissures present, dorsal seta blunt; second cheliceral segment length 56–60. Movable digit 17–18, with apical hook and one small tooth on cutting surface and with two ventral mucros: one strong spine-like in the middle of digit and second one small near base.
Legs (Fig. 4) — Lengths: I 274–313, II 231–243, III 216–236, IV 291–317. Leg chaetotaxy formulae normal for genus: leg I: coxa 2 (0 0/1 0/1 0), trochanter 6 (1 0/1 1/2 1), femur 12 (2 3/1 2/2 2), genu 13 (2 3/2 3/1 2), tibia 13 (2 3/2 3/1 2); leg II: coxa 2 (0 0/1 0/1 0), trochanter 5 (1 0/1 0/2 1), femur 11 (2 3/1 2/2 1), genu 11 (2 3/1 2/1 2), tibia 10 (2 2/1 2/1 2); leg III: coxa 2 (0 0/1 0/1 0), trochanter 5 (1 0/1 0/2 1), femur 6 (1 2/1 1/0 1), genu 9 (2 2/1 2/1 1), tibia 9 (2 1/1 2/1 2) pl2 present; leg IV: coxa 1 (0 0/1 0/0 0), trochanter 5 (1 0/1 0/2 1), femur 6 (1 2/1 1/0 1), genu 9 (2 2/1 3/0 1), tibia 10 (2 1/1 3/1 2). Tarsi II-IV: 18 (3 3/2 1/1 3/2 3). Most leg setae stout and inserted on small tubercles. All legs with elongate pretarsi, bearing paired claws, paradactyli and three rounded pulvillae.
Currently, fifteen species of the genus Proctolaelaps have been reported from North Asia: P. arctorotundus Nikolsky, 1984; P. bickleyi (Bram, 1956); P. bombophilus (Westerboer, 1963); P. dendroctoni Lindquist and Hunter, 1965; P. fiseri Samšiňák, 1960; P. hystricoides Lindquist and Hunter, 1965; P. hystrix (Vitzthum, 1923); P. jueradeus (Schweizer, 1949); P. longisetosus (Postner in Westerboer, 1963); P. ornatus (Postner in Westerboer, 1963); P. parvanalis (Thor, 1930); P. pseudofiseri Nikolsky, 1984; P. pygmaeus (Müller, 1859); P. scolyti Evans (1958); P. sibiriensis (Davydova, 1988) (Bregetova 1977a; Nikolsky 1984; Davydova and Nikolsky 1986; Davydova 1988; Davydova and Bogatyrev, 1990; Klimov 1998; Makarova, 2012; Marchenko, 2010, 2012; Khaustov et al. 2016, 2018; Trach and Khaustov, 2017).
Genus Proctolaelaps Berlese, 1923 includes about 140 described species, but only five species are associated with bumblebees: Proctolaelaps bombophilus (Westerboer, 1963); P. longanalis (Westerboer, 1963); P. longisetosus (Postner, 1963); P. ornatus (Postner, 1963); P. sibiriensis (Davydova, 1988).
Their distribution is limited to the Holarctic (e.g. P. sibiriensis is known only from Western Siberia). Although the genus Bombus Latreille, 1802 is more widely distributed, and data on Proctolaelaps mites associated with bumblebees in the Neotropical and Indomalayan regions are not recorded at all (Williams, 1998; OConnor, Klimov, 2012).
Nothing is known about the feeding behavior of these mites or any other aspects of their biology. Females of these species of mites disperse and overwinter on adult queen bees (Klimov et al., 2016). OConnor and Klimov (2012) are of the opinion that Proctolaelaps mites could be harmful to their bee hosts by feeding on its eggs, larvae, and pupae. However, we agree with Halliday (2019) that the mites and the bees have a symbiotic relationship though these suggestions are still mere speculation and not yet confirmed.
The following key is based on published descriptions and illustrations, except for P. ornatus and P. sibiriensis.
1. Dorsal shield strongly sculptured; setae j1 and z1 located on anterior extension of shield; anal shield subquadrate; setae of JV- and ZV-series short, never reaching base of consecutive seta
— Dorsal shield sculptured more lightly; anterior extension of shield absent; anal shield ovale or subrectangle; setae of JV- and ZV-series longer, mostly reaching base of next consecutive seta
2. Setae of dorsal shield shorter than distances to setae next behind (Fig. 5C); circum-anal setae subequal (Fig. 5D); epistome triangular, pointed distally (Holarctic)
...... P. ornatus (Postner, 1963)
— Most setae of j-, z-, s-, and r-series reach base of seta next behind (Fig. 5A); post-anal seta 1.5–2 times as long as para-anal setae (Fig. 5B); epistome subtriangular with small blunt process distally and undulated laterally (Palaearctic: Western Siberia)
...... P. sibiriensis (Davydova, 1988)
3. Epistomal margin denticulate; fixed digit of chelicera with numerous teeth (Holarctic)
...... P. longanalis (Westerboer, 1963)
— Epistomal margin smooth; fixed digit of chelicera with one or two teeth
4. Setae of dorsal shield significantly longer than distances to setae next behind; deutosternum with rows of denticles 1 to 5 connected by lateral margins, and rows 6–7 free; movable cheliceral digit with one tooth (Holarctic)
...... P. longisetosus (Postner, 1963)
— Setae of dorsal shield as long as distances to setae next behind; deutosternum with all 7 rows of denticles connected; movable cheliceral digit with two teeth (Holarctic)
...... P. bombophilus (Westerboer, 1963)
We are very grateful to the reviewers for their comments. We also thank Dr. Edward A. Ueckermann (School of Environmental Sciences and Development, Potchefstroom Campus, North-West University, South Africa) for his valuable suggestions and the English correction. The study of I.I. Marchenko was supported by the Russian Federal Fundamental Scientific Research Program AAAA-A16-116121.
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