Tuckerella fossilibus Khaustov, Sergeyenko & Perkovsky, 2014

Sidorchuk, Ekaterina A. & Khaustov, Alexander A., 2018, Two Eocene species of peacock mites (Acari: Tetranychoidea: Tuckerellidae), Acarologia 58 (1), pp. 99-115 : 106-110

Tuckerella fossilibus Khaustov, Sergeyenko & Perkovsky, 2014 .

( Figs 5–7 )

Tuckerella fossilibus Khaustov, Sergeyenko & Perkovsky, 2014, p. 367 , Figures 1–5 .

Redescription — Deutonymph. Length of idiosoma – 245, width – 165.

Gnathosoma ( Figs 5D , 7B, C ) — Left palp covers main part of right palp dorsally, both palps preserved in a way to cover infracapitulum dorsally. Palpgenu dorsally with seta d slightly not reaching base of tibial claw. Palptibia with large, hooked tibial claw and three pairs of setae: d slightly longer than length of palpgenu; short l”, reaching to tip of tibial claw; medium-sized l’, about length of palptibia+tibial claw. Inner margin of tibial claw transversely striate. Palptarsus with 5 visible phaneres: 3 terminal, blunt-ended (probably palpal eupathidia), one short dorsal and one short ventral. Subcapitulum long and narrow with visible stylet protruding apically ( Figs 5D , 7B , st); ventrally with one pair of long subcapitular setae m. Peritremes not evident. Oval stylophore, ca 100x40, visible inside body ( Figs 5A , 6 , sty).

Idiosomal dorsum ( Figs 5 , 6 , 7B ) — Cuticular ornamentation, where visible anterodorsally, irregularly reticulate ( Fig. 5A ). Number of dorsal idiosomal setae as in T. weiterschani n. sp. Setae v 2, sc 1 and sc 2 fan-like ( Fig. 5C, D ); v 1 considerably different from other prodorsal setae, with smooth margins and weakly tapered tip ( Figs. 5D , 7 ). Two pairs of eyes located anterolaterally to bases of setae sc 1; posterior eye distinctly larger than anterior ( Fig. 7B , oc). All setae of C, D, E and F-rows broad, flat, ovate to obovate in shape: c 1 - c 3, d 1 - d 3 and e 1, e 2 of medium size, subequal (16 – 18 x 24 – 28); f 1 and f 2 slightly smaller than e 1 and e 2; f 2 situated on same transverse level as f 1. Lateral setae c 5 - c 7, d 4 - d6 and e3 distinctly larger than central, more elongate, with rounded tips, largest d 6 28 x 60. Setae h 1 large, flat, obovate (27 x 55), setae h 2 – h 8 flagellate: h 2, h 4, h 5, h 7 long, barbed, tapered (180, 270, 180, 220 respectively), h 6 short, thick, heavily barbed, blunt (40); h 3, h 8 intermediate in length and thickness, barbed, tapered (80). Only anterior margins of dorsal shields C and D clearly visible ( Fig. 6 ).

Idiosomal venter ( Figs 5B , 7A, D, E, F ) — Dark and collapsed, obscured by legs. Only coxal setae are partly discernible: 1a-c and 2b smooth, fine, 1a longest; 2c long, thick, heavily barbed. Genital and anal openings indiscernible.

Legs ( Fig. 7 ) — Dark and curled, mostly visible in ventral aspect, with some setae poorly discernible. Leg I ( Fig. 7A, B ): trochanter without visible setae; femur with three large obovate setae ( d, l’, l”) and setiform bv”, other ventral setae not visible. Genu with three large obovate setae ( d, l’, l”) and setiform v”, other ventral setae not visible. Tibia with large, obovate seta l” and narrower d, l’; ventral setae not visible; solenidion φ baculiform, situated on short tubercle. Tarsus with two claws and empodium, each with clearly visible tenent hairs; two solenidia present, ω 1 about 2 times longer than ω 2; setae: ( u) simple and short, abaxial ” () members of pairs ( ft) and ( pl) long, distinctly longer than tarsus, pl’ about half shorter on right leg, absent on left leg; ( tc) situated on tubercles, fine, tapered, ( p) blunt, short, apparently eupathidial, difficult to discern where hidden behind ambulacrum; pv’ setiform. Leg II ( Fig. 7C, D ): trochanter not discernible; femur with long, thick, heavily barbed seta bv” and 3 obovate large setae d and ( l) ( d and l” artificially split on left leg); genu with 3 obovate setae visible; tibia with 3 obovate and one or two long simple seta visible (( v) on left, only v” on right leg); tarsus with ambulacrum as in leg I (well visible on right leg), one solenidion, and 10 smooth setae: long ft”, shorter ft’, ( pl), ( tc), ( u) (one member of pair visible on each leg), p” and pv’. Leg III ( Fig. 7E, F ): trochanter with single visible seta l’ thick, long, heavily barbed; femur with small obovate seta d and smooth simple ev ’; genu with single visible small obovate seta l’; tibia with 2 clearly visible setae, simple v ’ and small obovate l’ (visible transversally on right leg), and one spot that may be alveolus of seta d; tarsus with ambulacrum like in leg II and 7 simple setae (only 4 clearly visible on right leg): ( ft), ( tc), ( u) and pv’. Leg IV ( Fig. 7 H, J ): poorly visible, dark, trochanter and setation of femur indiscernible; genu with one well visible narrowly obovate seta d on left leg, no visible setae on right; tibia with 2 ventral setae well visible, two discernible on right leg, one well visible seta and one discernible on left; tarsus with two claws discernible, 3 setae visible on left and one on right leg. See figure for possible setal homologies. Observed setation (trochanter to tarsus, solenidia in parentheses): leg I:?-5-3-4(1)-11(2); leg II:?-4-3-5-10(1); leg III: 1-2-1-2/3?-7; leg IV:?-?-1-2?/4?-?.

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Remarks — Khaustov et al. (2014) in original description of T. fossilibus were not able to identify its life stage. Now, after more detailed description we can suggest that it is probably a deutonymph. Our opinion is based on the setation of leg I, which shows: (1) two tarsal solenidia, (2) absence of the tarsal seta l 1 ’, (3) three obovate setae on each genu and tibia. According to observations by Quiros-Gonzalez and Baker (1984), Lindquist (1985), Beard and Walter (2005) and Beard et al. 2013, although there is some interspecific variation, the second tarsal solenidion is deutonymphal, tarsal seta l 1 ’ is tritonymphal, and three obovate setae on first genu and tibia are only present in deutonymphs: known protonymphs are found to have 1–2 obovate setae per segment, while tritonymphs and adults have five.

Addition to the differential diagnosis — Certain caution is necessary when using this comparison, for the immature specimen is being compared to adults. Based on the available descriptions ( Quiros-Gonzalez and Baker 1984, Lindquist 1985, Beard and Walter 2005, Beard et al. 2013), ontogenetic changes of the opisthonotal setation may affect setae v 1 (in T. revelata they are obovate, with rough edge, in larva, with outline smoothing out in the subsequent stages), leaf-shaped C-H-row setae (relatively narrower and more tapered in the immatures) and flagellate H-row setae (becoming relatively shorter during ontogeny). T. fossilibus is so far unique tuckerellid species known to have obovate setae h 1 similar in size to the lateral setae of C-, D- and E rows. By the shape of proterosomal setae v 1 and the relative shortness of setae h 1 and h 6, deutonymphal T. fossilibus is similar to adults of T. pavoniformis ( Ewing, 1922) , T. indica Prasad, 1973 and T. channabasavannai Malik and Kumar, 1992 . It differs from them by much larger setae h 1 and by the differentiated shapes of the other H-row setae T. ( pavoniformis has setae h 2 - h 5, h 7 and h 8 all similar, whip-like ( Baker and Pritchard 1953), as do T. indica and T. channabasavannai ). By the shape of setae v 1 T. fossilibus is also similar to T. japonica Ehara, 1975 and to T. kumaonensis Gupta, 1979 , but these species have three pairs of comparatively small leaf-like setae in h -series.

Holotype container — Amber fragment with holotype, sized 2x1x 0.5 mm, is mounted in the Buehler EpoThin epoxy resin between two 1 cm coverslips. The preparation is glued with a low-temperature hot-melt adhesive to a 1.5 mm-thick transparent plastic frame ( Fig. 5A ).

Figures

Figure 1 Tuckerella weiterschani n. sp. holotype. Layered DIC micrographs: A – dorsal view, inserts show two aspects of amber piece containing holotype and its package, not to scale; B – ventral; C – posterior; D, E, details of idiosomal setae, ventral view; F, eyes; G, posterior idiosomal setae laterally; H, detail of prodorsal setav1 and peritreme; J, lateral aspect. Rectangles in A, B, J show positions of Figs D-G. Abbreviations: an, anal area; ge, genital area; oc, eyes, per, peritreme; plp, palp; sub, subcapitulum; I–IV, legs.

Figure 2 Tuckerella weiterschani n. sp. holotype. Layered POL micrograph. Gnathosoma laterally, arrow points to adoral seta. Abbreviations: palp segments: Fe, femur; Ge, genu; Ta, tarsus; Ti, tibia; ti.cl, palptibial claw.

Figure 3 Tuckerella weiterschani n. sp. holotype dorsally.

Figure 4 Tuckerella weiterschani n. sp. holotype details. A’, right tarsus I adaxially; A, left leg I abaxially, gnathosoma and anterior idiosoma dorsally; B, leg II abaxially; C, leg III abaxially; D, leg IV abaxially; D’, tarsus and tibia IV dorsally. Abbreviations: oc, eyes; per, peritreme; plp, left (poorly visible) palp; sub, subcapitulum; ti.cl, palptibial claw. Gray lines represent poorly discernible structures.

Figure 5 Tuckerella fossilibus Khaustov, Sergeyenko & Perkovsky, 2014 holotype deutonymph. Layered DIC micrographs: A – dorsal view, rectangles show positions of figures C, D, insert shows container with holotype; B – ventral; C – detail of idiosomal setae; D – left leg I and anterior proterosoma dorsally. Abbreviations: st, cheliceral stylets; sty, stylophore; ta, palptarsus; ti.cl, palptibial claw.

Figure 6 Tuckerella fossilibus Khaustov, Sergeyenko & Perkovsky, 2014 holotype deutonymph dorsally. Abbreviation: sty, stylophore.

Figure 7 Tuckerella fossilibus Khaustov, Sergeyenko & Perkovsky, 2014 holotype deutonymph detail: A – right tarsus I in ventral view of mite; B – leg I, gnathosoma and anterior proterosoma, dorsal view; C–J, legs in ventral view of mite: C – right leg II; D – left leg II and seta 3a; E – right leg III F – left leg III; H – right leg IV; J – left leg IV. Abbreviations: oc, eyes; st, cheliceral stylets; ta, palptarsus; ti.cl, palptibial claw. Gray lines represent poorly discernible structures.