Tarsonemus striatus, Khaustov, 2017

Khaustov, Alexander A., 2017, A new species of Tarsonemus (Acari: Tarsonemidae) associated with the bark beetle, Polygraphus proximus (Coleoptera: Curculionidae: Scolytinae) from the Far East of Russia, Acarologia 57 (3), pp. 673-687 : 674-685

Tarsonemus striatus n. sp.

( Figures 1-11 )

Zoobank: AAE737EE-99B0-4A20-B8AE-9293AC340DDE

Description

Female ( Figures 1-4 , 11 ) — Length of idiosoma

180 (170-190), width 110 (105-125).

Gnathosoma — Gnathosomal capsule subtriangular, slightly longer than its width. Length of gnathosomal capsule 29 (27-29), width 23 (20-23). Dorsomedian apodeme well developed, extending nearly entire distance from union basally with circumcapitular apodeme to level of insertion of dorsal gnathosomal setae (ch). Gnathosoma with dorsal pair of setae ch 13 (13-14) subequal to subcapitular setae su 13 (12-13); both setae slender and smooth. Palpcoxal setae (pp) subequal to ch, slen- der and pointed. Palps short 8 (7-8) cylindrical, with short dorsolateral setae. Pharynx ( Figure 2D ) with well-developed muscular sheath and with inconspicuous pair of glandular structures at its posterior extremity.

Idiosomal dorsum ( Figures 1A , 2 A-C, 11C) — Prodorsal shield with distinct linear microsculpture ( Figure 2A ); margin of shield distinctively triarcuate anteriorly and laterally, although lateral arches sometimes inconspicuous if folded ventrally. Prodorsum without median apodeme. Tracheal trunks without sclerotized sacs. Pseudostigmatic organs capitate, ellipsoidal, finely spiculate but with two larger spicules apically, and completely covered by prodorsal shield. All hysterosomal tergites with fine longitudinal striation ( Figures 2 B-C, 11C). Setae v 1, sc 2, c 1 and c 2 smooth and pointed; setae d and f weakly barbed and pointed; setae e and h blunt-ended and weakly barbed. Posterior margin of tergite C distinctly undulate ( Figures 2 B-C, 11C), posterior margin of tergite D sometimes also weakly undulate. Lengths of dorsal setae: v 1 18 (17 - 19), sc 2 36 (34 - 36), c 1 21 (17 - 22), c 2 25 (22 - 26), d 14 (13-15), e 7 (6-7), f 20 (19-21), h 7 (6-7). Distances between setae: v 1 - v 1 26 (25-28), v 2 - v 2 36 (35-37), sc 2 - sc 2 39 (38-40), c 1 - c 1 60 (59-63), c 2 - c 2 97 (91-98), c 1 - c 2 34 (31-34), d-d 36 (34-37), e-e 71 (66-72), e-f 28 (26-30), f -f 15 (14-15), h-h 39 (36-39).

Idiosomal venter ( Figures 1B , 2 E-F) — Prosternal apodeme (appr) extending posteriad only slightly beyond apodemes 2 (ap2), and with nodule between apodemes 1 (ap1) and ap2. Ap2 very slightly curved, and ending with small nodule medially. Sejugal apodeme (apsej) well developed, continuous, and with few weak processes directed anteriorly. Anterior sternal plate with uniform, very small dimples ( Figure 2F ). Setae 1 a needle-like; 2 a pointed, smooth. Apodemes 3 (ap3) united medially to form one continuous, subsurface band across metapodosomal venter, and extending laterally beyond anterior extremities of trochanters III. Setae 3 a and 3 b minute, needle-like. Apodemes 4 (ap4) reach- ing slightly posteriad of 3 b bases. Tegula rounded, short, flanked on either side by short, curved, conspicuous line. Posterior sternal plate with distinctly larger dimples in central part and smaller laterally ( Figure 2E ). Pseudanal setae smooth, pointed, about as long as distance between their bases. Lengths of ventral setae: 1 a 7 (7), 2 a 9 (7-9), 3 a 4 (4), 3 b 5 (5-6), ps 10 (7-10). Width of tegula 13 (12-13).

Legs ( Figures 3-4 ) — Legs: chaetotaxy (including unguinal setae u’, u” on tibiotarsus I and u” on tarsi II and III) of leg I: Fe4-Ge4-TiTa6(2F)+10(1ř); leg II: Fe3-Ge3-Ti4-Ta7(1ř); leg III: FeGe1+3-Ti4-Ta5. Lengths of legs: I 60 (56-60), II 58 (55-58), III 53 (49- 54), IV 32 (30-33). Leg I ( Figure 3A ). Solenidion ř capitate, with slightly pointed tip; solenidia F 1 and F 2 capitate; seta k 7 (6-7) rod-shaped, slightly longer than solenidion F 1. Lengths of solenidia: ř 6 (6) = F 1 6 (5-6)> F 2 4 (3-4). Seta d of femur slightly thickened, blunt-ended and smooth; seta s slightly thickened, spiniform; unguinal setae (u) short, blunt-ended; setae l” of femur, (l) and v’ of genu blunt-ended and smooth; seta l’ of femur distinctly barbed and slightly blunt-ended, seta v” of femur distinctly barbed and pointed; other leg setae (except eupathidia) pointed and smooth. Femur with weak flange near base of seta v”. Leg II (Figure 3B). Solenidion ř 4 (4) capitate. Setae pl” and u’ spine-like; setae l’ of femur, l’ of genu, and tc’ of tarsus blunt-ended and weakly barbed; seta d of femur needle-like; setae v’ of genu and l’ of tibia slightly blunt-ended and smooth; setae v” of femur, l” of genu, and (v) of tibia long, pointed and weakly barbed; other leg setae pointed and smooth. Leg III ( Figure 4A ). Setae v’ of femur and l’ of genu needlelike; setae v’ of genu and l’ of tibia blunt-ended and weakly barbed; seta u’ slightly thickened, spiniform; other leg setae pointed and smooth. Leg IV ( Figure 4B ). Seta v’ of femur slightly blunt-ended, smooth; other leg setae pointed and smooth.

Male ( Figures 5-8 ) — Length of idiosoma 125-150, width 85-95.

Gnathosoma — Gnathosomal capsule, including pharyngeal structures, similar to that of female. Length of gnathosomal capsule 21-23, width 16-20. Lengths of gnathosomal setae: ch 11-13, su 10-12.

Idiosomal dorsum ( Figures 5A , 8 A-B) — Prodorsal shield weakly sclerotized, with poorly defined edges, subtriangular, with weak linear microsculpture and small uniform dimples ( Figure 8A ). All dorsal setae smooth; setae c 1 and d blunt-ended; other dorsal setae pointed. Tergite CD with delicate longitudinal striation and very small dimples ( Figure 8B ). Tergite EF smooth, with two arch-like lines. Cupules ia situated posteromedially to bases of c 1; cupules im situated just anterolaterally to bases of setae f. Lengths of dorsal setae: v 1 18 - 22, v 2 10 - 12, sc 1 43 - 48, sc 2 18 - 19, c 1 13 - 16, c 2 27 - 31, d 14-18, f 12- 14. Distances between setae: v 1 - v 1 12-13, v 2 - v 2 22-23, sc 1 - sc 1 26-28, sc 2 - sc 2 42-43, c 1 - c 1 68-77, c 2 - c 2 74-84, c 1 - c 2 28-29, d -d 35-40, f -f 21-23.

Idiosomal venter ( Figures 5B , 8C ) — Appr extending posteriorly to posterior edge of prosternal plate, but weakened along its posterior half between ap1 and ap2. Ap2 straight, not uniting with appr. Apsej indistinct. Setae 1 a and 2 a inserted well behind ap1 and ap2, respectively. All ventral setae smooth; setae 1 a needle-like, other ventral setae pointed. Anterior and posterior sternal plates with uniform, very small dimples ( Figure 8C ). Ap3, ap4, and apodemes 5 (ap5) well developed. Setae 3 a inserted between anterior ends of ap3 and ap4; setae 3 b inserted on ap4 Lengths of ventral setae: 1 a 7-8, 2 a 11-12, 3 a 18-21, 3 b 17-20.

Legs ( Figures 6-7 ) — Legs: chaetotaxy of leg I: Fe4-Ge4-Ti6(2F)-Ta10(1ř); leg II: Fe3-Ge3- Ti4-Ta6(1ř); leg III: Fe1-Ge3-Ti4-Ta6; leg IV: Tr1- FeGe1+2-Ti1(1F)-Ta3. Lengths of legs: I 53-59, II 51-62, III 64-71, IV 50-66. Leg I ( Figure 6A ). Solenidia on tibia and tarsus I as in female. Lengths of solenidia: ř 3-4> F 1 4-5> F 2 3; seta k 5-6. Seta d, (l) of femur, l’, v’ of genu, l’, v’ of tibia, and (ft) of tarsus blunt-ended and smooth; seta s slightly thickened, spiniform; setae v” of tibia weakly barbed and pointed; other leg setae (except eupathidia) pointed and smooth. Leg II ( Figure 6B ). Solenidion ř 5 capitate. Setae pl” and u’ spine-like; setae l’ of genu and tc’ of tarsus blunt-ended and weakly barbed; seta d, l’ of femur, v’ of genu, and l’ of tibia needlelike; setae v” of femur, (v) of tibia and pv” of tarsus long, pointed and weakly barbed; other leg setae pointed and smooth. Leg III ( Figure 7A ). Setae v’ of femur and l” of genu needle-like; setae v’ of genu blunt-ended and weakly barbed; setae l’ of tibia u’, pv” of tarsus thickened, spiniform; other leg setae pointed and smooth. Leg IV ( Figure 7B ) stout. Trochanter conspicuously punctate ( Figure 8C ). Femorogenu robust, with small projection near base of seta v’ of femur. Setae l” of genu and v’ of tibia weakly barbed, blunt-ended; all tarsal setae needle-like; other leg setae pointed and smooth. Seta v’ of tibia almost as long as leg IV. Tarsal claw strongly developed. Solenidion F 4 rod-shaped.

Larva ( Figures 9 , 10 ) — Length of idiosoma 140-

150, width 83-92.

Gnathosoma — Gnathosomal capsule, including pharyngeal structures, similar to that of female, but palpcoxal setae not evident. Length of gnathosomal capsule 25-28, width 19-20. Lengths of gnathosomal setae: ch 13-14, su 11-13.

Idiosomal dorsum ( Figure 9A ) — Dorsal shields of idiosoma weakly sclerotized, smooth. Prodorsal shield subtriangular. Dorsal setae c 2 smooth, pointed; other dorsal setae distinctly blunt-ended and barbed. Posterior margin of tergite C deeply concave. Segment HPs almost completely covered by tergite EF. Setae h 1 long, slightly rounded at the

Khaustov A.A.

tip. Lengths of dorsal setae: v 1 9 - 10, sc 1 10 - 11, sc 2 28 - 29, c 1 9 - 11, c 2 17 - 18, d 10-11, e 14-16, f 17-21, h 1 31- 33, h 2 14. Distances between setae: v 1 - v 1 10, sc 1 - sc 1 40-41, sc 2 - sc 2 37-40, c 1 - c 1 67-69, d-d 29-30, e-f 16-17, f -f 8-11, h 1 - h 1 5, h 2 - h 2 15.

Idiosomal venter ( Figure 9B ) — Ventral plates of idiosoma weakly sclerotized, smooth. Ap1 longer than in adults, ap2 curving posteromedially, not uniting with appr. All ventral setae smooth; setae 1 a, 2 a and 3 b needle-like, other ventral setae pointed. Lengths of ventral setae: 1 a 7, 2 a 7, 3 a 10-13, 3 b 8-9, ps 1,2 5-7.

Legs ( Figure 10 ) — Legs: chaetotaxy of leg I: Fe4- Ge4-Ti6(1F)-Ta8(1ř); leg II: Fe3-Ge3-Ti4-Ta7(1ř); leg III: Fe1-Ge3-Ti4-Ta6. Lengths of legs: I 46-47, II 44- 46, III 46-47. Leg I ( Figure 10A ). Solenidia on tibia and tarsus I capitate. Lengths of solenidia: ř 4 = F 1 4; seta k 5. All setae of leg I smooth. Seta d, (l) of femur, all setae of genu, l”, v’ of tibia, and (u) of tarsus needle-like; seta s slightly thickened, spiniform; other leg setae (except eupathidia) pointed and smooth. Leg II ( Figure 10B ). Solenidion ř 3- 4 capitate. All leg setae smooth. Setae pl” and u’ spine-like; setae d, l’ of femur, l’, v’ of genu, l’ of tibia, and u” of tarsus needle-like; seta tc’ of tar-

Acarologia 57(3): 673–687 (2017)

sus slightly thickened, blunt-ended; other leg setae pointed. Leg III ( Figure 10C ). All leg setae smooth. Setae v’ of femur and (l) of genu needle-like; setae l’ of tibia u’, pv” of tarsus thickened, spiniform; other leg setae pointed and smooth.

Type material — Female holotype, slide AK280816, Primorsky Krai, Lazo reg., 43°30’04.6”N, 133°34’47.1”E, 902 m. a.s.l., 28 August 2016, between coxae I and II of adult bark beetle Polygraphus proximus Blandford, 1894 under the bark of Manchurian fir ( Abies nephrolēpis ), coll. A.A. Khaustov. Paratypes: 18 females, same data; 1 female, 3 males and 5 larvae, same locality and date, but in the galleries of Polygraphus proximus under the bark of Manchurian fir.

Etymology — The specific epithet of the new species is derived from Latin word striatus meaning striate and refers to the presence of distinct linear microsculpture on the idiosomal tergites of the female and male.

Differential diagnosis — The female of the new species is very similar to T. triarcus Lindquist, 1969 , described from North America, in having a triarcuate prodorsal shield, continuous ap3, and similar shape and position of idiosomal setae. The female of the new species differs from T. triarcus by the presence of distinct linear microsculpture on the idiosomal tergites (absent in T. triarcus ), undulate posterior margin of tergite C (not undulate in T. triarcus ), and by the absence of seta pv” on tarsus III (present in T. triarcus ). The male of the new species differs from the male of T. triarcus by the presence of weak linear microsculpture on the idiosomal tergites (absent in T. triarcus ) and presence of a short projection near the base of seta v’ of femur IV (absent in T. triarcus ).

Figures

FIGURE 1: Tarsonemus striatus n. sp., female: A – dorsum of the body; B – venter of the body.

FIGURE 2: DIC micrographs of Tarsonemus striatus n. sp. female: A – central part of prodorsal shield; B – central part of tergite C; C – central parts of tergites D and EF; D – pharynx; E – central part of posterior sternal plate; F – central part of anterior sternal plate.

FIGURE 3: Tarsonemus striatus n. sp., female: A – left leg I in dorsal view; B – left leg II in dorsal view.

FIGURE 4: Tarsonemus striatus n. sp., female: A – left leg III in ventral view; B – left leg IV in ventral view.

FIGURE 5: Tarsonemus striatus n. sp., male: A – dorsum of the body; B – venter of the body

FIGURE 6: Tarsonemus striatus n. sp., male: A – left leg I in dorsal view; B – left leg II in dorsal view.

FIGURE 7: Tarsonemus striatus n. sp., male: A – left leg III in dorsal view; B – left leg IV in dorsal view.

FIGURE 8: DIC micrographs of Tarsonemus striatus n. sp. male: A – central part of prodorsal shield; B – central part of tergite CD; C – right part of posterior sternal plate.

FIGURE 9: Tarsonemus striatus n. sp., larva: A – dorsum of the body; B – venter of the body.

FIGURE 10: Tarsonemus striatus n. sp., larva: A – right leg I in dorsal view; B – right leg II in dorsal view; C – right leg III in dorsal view.

FIGURE 11: SEM micrographs of Tarsonemus striatus n. sp. females, phoretic on four-eyed fir bark beetle, Polygraphus proximus: A – ventral view of the beetle with phoretic mite (arrow); B, C – detailed view.