Amblyseius silvaticus (Chant)

Khaustov, Vladimir A., 2020, Review of Amblyseius Berlese (Acari: Phytoseiidae) in Western Siberia, Russia, Acarologia 60 (4), pp. 769-805 : 770-778

Amblyseius silvaticus (Chant) ( Figs. 1-8 , 26A )

Typhlodromus (Amblyseius) silvaticus Chant, 1959: 94 , Figs. 216, 217.

Amblyseius (Amblyseius) sylvaticus (sic): Muma 1961: 287.

Typhlodromus silvaticus: Hirschmann 1962: 24 .

Amblyseius (Amblyseius) silvaticus : Denmark & Muma 1989: 73.

Amblyseius patrius Karg, 1970: 295 (synonymized by Denmark & Muma, 1989: 73).

Material examined — two females, Russia, Tyumen province, vicinity of Tyunevo, 57°22 ′

N, 65°41 ′ E, 25 September 2018, A. Khaustov coll., on mushrooms of Armillaria genus; 8 females and 5 males, Russia, Tyumen province, Uspenka state zoological reserve, 57°04 ′ N, 65°04 ′ E, 28 June 2019, A. Khaustov coll., on bark of Picea obovata Ledeb. , Pinus sylvestris

L., ( Pinaceae ) and Betula pendula Roth. , ( Betulaceae ).

World distribution — Cuba, England, Finland, Norway, Switzerland ( Demite et al. 2020). Redescription — Female ( Figs. 1 , 2 B-2H, 3, 4, 6, 7A, 7B, 7D, 7E, 26A) (n = 10)

Idiosomal setal pattern – 10A:9B/JV–3:ZV.

Dorsal idiosoma ( Figs. 1A , 7A ) – Dorsal shield oval, smooth, 372 (351-386) long and 250 (240-266) wide; with 19 pairs of setae (included r3 and R 1), all setae smooth, except J5, Z4 and Z5, slightly barbed; length of setae: j1 34 (30-38), j3 61 (58-67), j4 6 (5-7), j5 5 (4-6), j6

6 (5-7), J2 6 (5-6), J5 9 (8-10), z2 20 (18-21), z4 37 (31-43), z5 5 (5-6), Z1 6 (5-7), Z4 146 (134-160), Z5 247 (233-258), s4 113 (107-116), S2 7 (7-9), S4 7 (6-7), S5 7 (6-8); setae r3 26 (24-28) and R 1 9 (8-9) on lateral soft cuticle; dorsal shield with seven pairs of solenostomes (gd1, gd2, gd4, gd5, gd6, gd8, gd9) and 16 pairs of poroids.

Gnathosoma ( Figs. 2A – 2D, 2F, 2G ) – Anterior margin of epistome bump-like and smooth. Hypostomal groove with seven transverse rows of denticles, each row with two teeth; subcapitular setae h1, h2, h3 subequal (28-30), slightly shorter than palp coxal setae (pc) 34-35. Chaetotaxy of palps: trochanter with two setae v1, v2; femur with five setae, thickened and apically spatulate antero-lateral al, three dorsal (d1, d2, d3) and one postero-lateral (pl); genu with six setae, antero-lateral setae (al1 and al2) thickened, three dorsal setae d (1, d2, d3) and one postero-lateral (pl); tibia with 14 setae, one antero-lateral (al), eight dorsal d1 – 8, two setae di-1, di-2, arise from the dorsal surface at the distal end, two ventral v (1, v2) and one postero-lateral (pl); tarsus with 15 setae (six simple d1, d2, d3, v1, v2, v3; nine stout setae with rounded tips di-1 to di- 9) and two-tined apotele ( Fig. 2C ).

Chelicera ( Figs. 2B , 7D ) – fixed digit 34 (31-37) long, with 10-11 teeth and pilus dentilis; movable digit 34 (31-38) long, with three teeth.

Ventral idiosoma ( Figs. 1B , 7B ) – Tritosternum with paired pilose laciniae 96-97, fused basally 41-44, columnar base 16-17 × 12-13 wide. Sternal shield smooth, 71 (68-72) long and 80 (78-82) wide, with three pairs of setae ST1 38 (35-43), ST2 32 (30-35), ST3 32 (31-33) and two pairs of lyrifissures iv1, iv2. Setae ST4 34 (32-36) located on small separate metasternal platelets, each with one pore iv3.

Genital shield smooth, 80 (75-84) wide at level of base of setae ST5 35 (32-38), para-genital poroids iv5 on soft cuticle.

Opisthosomatic venter with two pairs of elongated metapodal platelets, primary 24 (22-27) and accessory 16 (12-19) long; four pairs of setae, ZV1 21 (19-24), ZV3 14 (12-16), JV4 16 (13-17), JV5 103 (92-109) long, all smooth, and four pairs of poroids.

Ventrianal shield pentagonal in shape, smooth, 120 (115-125) long and 96 (92-100) wide at level of setae ZV2, with three pairs of pre-anal setae JV1 23 (22-25), ZV2 21 (20-25), JV2 25 (23-26), with small rounded pre-anal pores gv3 (distance between pores 45 (43-47)); para-anal setae 22 (21-23) and post-anal seta 26 (24-28).

Peritreme ( Figs. 1A , 2H ) – extends anteriorly to setae j1.

Spermatheca ( Figs. 2E , 7E ) – Calyx bell-shaped, 10 (8-13) long and at the opening 8 (7-11) wide, sides of calyx curved; atrium C-shaped, connected without neck with calyx; major duct thick, minor duct not visible.

Legs ( Figs. 3 , 4 ) – Legs I 393 (386-405) and IV 425 (412-429) longer than legs II 320 (313-329) and III 320 (317-329). Chaetotaxy normal for phytoseiid mites: Leg I: coxa 0 0/1

0/1 0, trochanter 1 0/1 0/2 1, femur 2 3/1 2/2 2, genu 2 2/1 2/1 2, tibia 2 2/1 2/1 2. Leg II: coxa

0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 2 3/1 2/1 1, genu 2 2/0 2/0 1, tibia 1 2/1 1/1 1. Leg III: coxa 0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 1 2/1 1/0 1, genu 1 2/1 2/0 1, tibia 1 1/1 2/1 1. Leg IV: coxa 0 0/1 0/0 0, trochanter 1 0/1 0/2 1, femur 1 2/1 1/0 1, genu 1 2/1 2/0 1, tibia 1 1/1 2/0 1. Chaetotaxy of tarsi II-IV typical for Phytoseiidae and bears 18 setae 3 3/2 3/2 3 + mv, md. Tarsus I with 37 setae, excluding apical sensorial setal cluster. Setae d3 13-15 with rounded tip, d4 30-34. Apical sensorial setal cluster ( Fig. 26A ) includes 10 short setae of different shape. Setae df-1 (12-14), df-3 (7-8) and df-7 (6-7) finger-shaped with blunt tips. Setae df-2 (5-6), df-5 (6-8), df-6 (12-13) and df-8 (11-12) baculiform with rounded tips, setae df-8 usually curved. Setae df-4 (8-9), df-9 (8-9) spur-like with lobe-like tips, setae df-10 (5-6) located between df-4 and df-9 also spur-like with acuminate tip. Measurements of macrosetae as follows: SgeI 36 (35-39), SgeII 40 (38-41), SgeIII 64 (58-73), SgeIV 143 (132-153), StiIII 43 (40-46), StiIV 108 (102-117), StIV 84 (78-93). All macrosetae are acuminate.

Male ( Figs. 2A , 5 , 7C , 8 ) (n = 5)

Idiosomal setal pattern – 10A:9B/JV-3,4:ZV-1,3.

Dorsal idiosoma ( Figs. 5A , 8A ) – Dorsal shield oval, smooth, 312 (306-316) long and 226 wide. As in female, dorsal shield with 19 pairs of setae, most of which smooth, except Z4 and Z5, slightly barbed. Setae r3 located on dorsal shield, setae R 1 on lateral soft cuticle or on dorsal shield. Length of dorsal setae as follows: j1 29 (27-30), j3 49 (46-52), j4 5 (4-7), j5 5 (4-5), j6 5 (5-6), J2 5 (5-6), J5 8 (7-8), z2 18 (17-18), z4 29 (28-32), z5 5 (4-5), Z1 5, Z4 106 (104-118), Z5 168 (163-174), s4 84 (81-91), S2 7, S4 6 (5-6), S5 5 (5-6), r3 18 (17-20), R 1 6 (5-6). Number and location of solenostomes and pores as in female, except gd3, which situated on dorsal shield posteriad base of setae s4.

Ventral idiosoma ( Figs. 5B , 8B ) – Sternogenital shield smooth with few sclerotized lines laterally, 125 (123-127) long (ST1- ST 5) and 70 (69-72) wide (ST2- ST 2); five pairs of setae ST1

30 (25-31), ST2 23 (21-26), ST3 24 (22-26), ST4 22 (20-25), ST5 22 (20-23) and three pairs of lyrifissures iv1, iv2, iv3.

Ventrianal shield reticulated only in anterior part, with three pairs of pre-anal setae JV1 17 (16-18), JV2 20 (17-22), ZV2 17 (16-20), one pair of anal setae PA 17 (16-17) and post-anal setae PST 20 (20-21), a pair of pre-anal pores gv3, posteriad base of setae JV2 and four pairs of poroids iv5, iv0, iv0, iv0. Ventrianal shield 139 (136-146) long, measured along midline; 185 (178-196) wide at level of anterolateral corners. Opisthogastric cuticle with one pair of setae

JV5 53 (50-57) and one pair of poroids ivp.

Chelicera ( Figs. 2A , 7C ) – Fixed digit 25 (23-26) long, with 9-10 teeth and pilus dentilis; movable digit 25 long with 1 tooth. Spermatodactyl as in Figs. 2A , 7C ; shaft of spermatodactyl 14 (13-14) long.

Legs – Legs I 344 (335-346) and IV 371 (367-374) longer than legs II 283 (278-289) and

III 288 (279-289). Legs chaetotaxy as in female. Measurements of macrosetae as follow: SgeII

33 (31-36), SgeIII 45 (41-47), SgeIV 97 (91-102), StiIII 36 (33-38), StiIV 72 (66-73), StIV 71 (67-75).

Remarks — In Denmark and Muma (1989), Amblyseius silvaticus is placed in the silvaticus species group. Also, Denmark and Muma (1989) synonymized A. silvaticus and A. patrius Karg. Karg and Huhta (2009) then removed this synonymy and updated the identification key of the species group. According to the key of Karg and Huhta (2009), the present specimens from Western Siberia are intermediate between A. silvaticus and A. tavasticus in having ratio lengths of setae z2 / z3 as in A. tavasticus and shape of spermatheca and length of setae Z5 as in A. silvaticus . Also, A. tavasticus in original description differs in number of teeth on fixed digit (14-16 versus 10-11 in the present Siberian specimens) and presence of delicate transverse lines on the dorsal shield. At my request, Drs Veikko Huhta (University of Jyväskylä, Finland) and Axel Christian (Senckenberg National Museum, Görlitz, Germany) examined paratypes of A. tavasticus deposited in Museum of Zoology, Helsinki, Finland and Senckenberg National Museum, Görlitz, Germany, respectively. They confirmed the absence of transverse lines on the dorsal shield. In specimens from Senckenberg National Museum, the number of teeth on fixed digit was about 10-11. The only relevant difference between A. silvaticus and A. tavasticus is thus the shape of calyx of spermatheca. In A. tavasticus it is wider than long, while in A. silvaticus the length and width of calyx is subequal (figure 2E). Siberian specimens show some variability in length/width ratio of calyx from equal length and width to length slightly longer than width. Both species have the same habitats and live on bark of trees, mainly in spruce forests. In my opinion, A. tavasticus is likely a potential junior synonym of A. silvaticus .

Figures

Figure 1 Amblyseius silvaticus (Chant, 1959), female: A – dorsal idiosoma, B – ventral idiosoma.

Figure 2 Amblyseius silvaticus (Chant, 1959), male: A – chelicera and spermatodactyle, female: B – chelicera, C – dorsal view of left palp tarsus, D – anterior margin of epistom, E – spermatheca, F – subcapitulum, G – left palp excepting tarsus, dorsal aspect, H – peritrema.

Figure 3 Amblyseius silvaticus (Chant, 1959), female: A–D – right legs I-IV, respectively, excepting tarsi, ventral view, macrosetae depicted in solid black.

Figure 4 Amblyseius silvaticus (Chant, 1959), female: right tarsi I-IV, respectively, macrosetae depicted in solid black: A – dorsal aspect; B – apical sensorial setal cluster area, C–E – ventral aspect.

Figure 5 Amblyseius silvaticus (Chant, 1959), male: A – dorsal idiosoma; B – ventral idiosoma.

Figure 6 SEM pictures of Amblyseius silvaticus (Chant, 1959), female: A – left tarsus of palp, dorsal aspect; B – right tarsus of palp, dorsal aspect; C – apical sensorial setal cluster area of tarsus I, left leg, dorsal aspect; D – apical sensorial setal cluster area of tarsus I, right leg, dorsal aspect.

Figure 7 Phase contrast (A, B) and DIC (C, D, E) pictures ofAmblyseius silvaticus (Chant, 1959). A – dorsal idiosoma of female, B – ventral idiosoma of female, C – chelicera of male with spermatodactyle, D – chelicera of female, E – spermatheca.

Figure 8 Phase contrast pictures ofAmblyseius silvaticus (Chant, 1959), male: A – dorsal idiosoma, B – ventral idiosoma.

Figure 26 Apical sensorial setal cluster area and setaed3 andd4 of tarsus I, female, right leg, dorsal aspect: A – Amblyseius silvaticus Chant, 1959; B – Amblyseius ampullosus Wu and Lan, 1991, C – Amblyseius krantzi Chant, 1959, D – Amblyseius meridionalis Berlese, 1914.