Eotetranychus spinophilus Zhang, Beard & Seeman, 2017

Zhang, Lanni, 2017, A new Australian species of Eotetranychus (Acari: Tetranychidae) from buck spinifex Triodia mitchelli (Poaceae), intraspecific variation in Eotetranychus, and the synonymy of Platytetranychus with Eotetranychus, Zootaxa 4324 (3), pp. 491-517 : 497-508

Eotetranychus spinophilus Zhang, Beard & Seeman sp. nov.

Figures 1–37

Diagnosis. Both sexes: Peritreme anastomosing; dorsal setae weakly barbed (each seta with minute distal fork); dorsocentral setae (c1, d1, e1, f1) generally relatively short: setae c1 much shorter than distance c1–d1; setae d1, e1, f1 about as long as distance to setal bases in next row. Tibiae III–IV with longitudinal striae mesally and with proximal and distal rings of transverse striae; tarsi III–IV with entirely longitudinal striae. Female: dorsal opisthosoma with mostly transverse striae; with some weakly arched striae between f1–f1; with longitudinal striae laterad c2 and d1–e1. Venter with mostly transverse striae; pregenital striae transverse, weak; genital striae transverse to weakly arched. Leg setal counts: trochanters 1, 1, 1, 1; femora 10, 7, 2, 2; genua 5, 5, 3, 3; tibiae 9 (1), 5, 5, 5; tarsi 15 (3+3), 12 (2+3), 8 (1+0), 8 (1+0). Male: dorsal opisthosoma with mostly transverse striae; with band of more widely-spaced transverse striae posteriad h1; with longitudinal striae laterad c2 and d1–e1. Aedeagus directed dorsally, strongly sigmoid, blunt-tipped; dorsal margin with distinct angle forming a weak yet distinct distal knob; ventral margin smoothly sigmoid.

Material examined. Holotype. ♀. Australia, ex. buck spinifex Triodia mitchellii Benth (Poaceae) , 90 km W Moonie, on Moonie Highway, Queensland, 27°56′57″S 149°31′19″E, 5.v.2007, J.J. Beard. Paratypes. 4 ♀♀, 5 ♂♂, 4 deutonymphs, data same as holotype. Holotype and 9 paratypes deposited in QM; 1 ♀, 1 ♂ paratype deposited in ANIC; 1 ♀, 1 ♂ paratype deposited in USNM.

Description. Adult female. Dorsum. ( Fig. 1 ) Body measurements: v2 –h1 255–261, sc2–sc2 145–170; idiosomal length 310–360, width 220–235. Distances between other setae: v2–v2 62 –72, sc1–sc1 85–92, c1–c1 53–58, c3–c3 176–213, d1–d1 44–53, d1–d 2 29–32, e1– e 1 53–59, e1– e 2 32–34, f1–f 1 30–33, h1–h 1 17–19; c1–d1 45–51, d1– e 1 30–33; e1–f1 40–45; f1–h 1 28–32. Prodorsal striae longitudinal; opisthosomal striae transverse medially between dorsocentral setae and arched between setae f1–f1, striae longitudinal to oblique laterally. Dorsal setae weakly barbed, with minute distal fork. Opisthosomal setae shorter than (c1, d1), or about as long as (c2, d2, e1–2, f1–2) distance to base of seta in next row. Setal lengths: v2 42 –51, sc1 45–56, sc2 45–56, c 1 31–42, c2 48–58, c3 53–64, d1 33–42, d2 43–54, e1 35 –43, e2 42 –55, f1 36–51, f2 44–56, h1 46–55, h2 33–38, h3 32–36.

Venter. ( Figs 2–3 ) Striae almost entirely transverse, without lobes; coxae with fine transverse striae; pregenital striae weak, transverse; striae on genital flap transverse to weakly arched, fine; genital region flanked by oblique to longitudinal striae; all ventral setae thin, smooth: 1a 19–29, 1b 24–30, 1c 37–46, 2b 28–34, 2c 44–55, 3a 13–19, 3b 29–34, 4a 19–22, 4b 28–33, ag 23–26, g 1 24–26, g 2 27–31, ps 1 16–21, ps 2 16–21.

Gnathosoma . ( Figs 8–12 ) Palp tarsus with short, broad spinneret (suζ) (2 wide, 5 long), one solenidion (4–5) and two eupathidia (Μl ′ 4–5, Μl" 5–6) ( Figs 11–12 ). Peritremes anastomosing ( Figs 8–10 ).

Spermatheca. ( Figs 4–7 ) A short narrow tube ending in small rounded (dorsal aspect Figs 4–5 ) to weakly reniform (lateral aspect Figs 6–7 ) bulb with honeycomb surface patterning.

Legs. ( Figs 13–19 ) Trochanters I–IV, femora I–IV, genua I–IV, tibiae I–II and proximal tarsi I–II with transverse striae; tibiae III–IV with mostly longitudinal striae except with proximal and distal rings of transverse striae; distal tarsi I–II with oblique–longitudinal striae; tarsi III–IV with longitudinal striae. Tarsus I ( Fig. 13 ) with two distal and adjacent duplex setae (solenidia: proximal ω ′ 31–33, distal ω" 42–46; companion fastigial setae: ft', ft" 8–10), single proximal solenidion (ω" 1 12–14), and three distal eupathidia (p'ζ, p"ζ 18–20; pv ′ζ 12–13); with three tactile setae and one solenidion (ω"1) proximal to or overlapping with bases of proximal duplex setae. Tibia I with single short solenidion φ 9–10. Tarsus II ( Fig. 15 ) with one duplex seta (solenidion ω" 26–31), proximal solenidion (ω" 1 9–11) and three distal eupathidia (p'ζ, p"ζ 18–20; pv ′ζ 12–13). Tarsus III ( Fig. 17 ) with single proximal solenidion (ω ′ 14–24). Tarsus IV ( Fig. 19 ) with single proximal solenidion (ω ′ 17–24). Empodia split into two sets of three proximoventral hairs, with proximal pair of hairs thicker than other two pairs ( Figs 14 , 16, 18 ). All leg setae finely barbed. Number of phaneres on legs I–IV:

Leg setation as shown in Figures 13 , 15, 17, 19 . Anomalies: one specimen with asymmetrical loss of tibia I seta l ′1, one specimen with asymmetrical addition of tibia I solenidion φ ′, one specimen with duplication (bases touching) of tarsus I seta v ′1.

Ontogenetic changes in leg setation. In general, most of the setae that are suppressed on the legs of E. spinophilus are adult setae. Here, femur I with ten setae in the adult matches the standard tetranychid chaetotaxy, as outlined in Lindquist (1985); however, femur II has seven setae, which has an extra seta present, l", that is not usually present on Tetranychinae spider mites. One to three of setae l', l" and v" are usually added to femur II of Bryobiinae deutonymphs, but usually none are added in Tetranychinae deutonymphs ( Lindquist, 1985). Parallel trends towards suppression of additional femoral setae on legs II–IV are found in other tetranychoid families, with no setae added in Linotetranidae and Tenuipalpidae . However, Tuckerellidae is similar to the Bryobiinae in adding l' and l" to femur II, but v" is suppressed. According to Lindquist (1985), the standard larval and protonymphal setae on femur II are d, v', bv", and no setae are added in the deutonymph. Therefore the deutonymph retains the larval complement on femur II, while three setae are added in the adult, l'1, l"1, v"1. Here, the deutonymph of E. spinophilus indeed has the standard larval complement of setae present, although we do not have a larva/ protonymph to unequivocally confirm it; and the standard three setae, along with the extra seta l", are added in the adult. Femora III–IV retain the larval/protonymphal complement of two setae, d and ev', in all known stages, meaning that two adult setae are not expressed on femur III–IV, i.e. l'1 and v'. Genua I–II have standard adult chaetotaxy of five setae present (d, l', l", v', v"), with seta d assumed to be added in the deutonymph as would be standard, and the remaining setae being larval. Genu III with three setae (d, l', v') is missing adult seta v" (n.b. seta d is assumed to be added in the deutonymph, as is typical). Genu IV with three setae (d, l', v') is missing adult seta v" (n.b. the expression of deutonymph seta d is delayed until the adult stage). Two setae are normally added to tibia I in the adult; however, only one of these setae is added in this species, v'1, while the other seta, v"1, is suppressed. It is assumed that the standard deutonymphal additions of l'1 and l"1 were made to tibia I in the deutonymph stage. Tibia II–IV all retain the larval complement of five setae (d, l', l", v', v"), with tibia II missing the two adult setae normally added, l'1 and v'1; tibia III is missing the one standard adult addition, v'1; and tibia IV is missing the two standard adult additions, l"1 and v'1. Tarsus I with 15 (3+3) setae is missing three setae, adult seta v'2, and two of the four standard deutonymph setae, v"1 and l"1. Tarsus II with 12 (2+3) setae is missing four setae, three of the four adult setae v'2, v"1, l'1 (ω"1 is added in adult as is standard), and the deutonymphal seta v'1. Tarsus III with 8 (1) setae is missing two setae, the single adult seta v'1 and the larval seta pv". Tarsus IV with 8 (1) setae is missing three setae, two of the three adult setae v'1 and v"1 (ω' is added), and the larval seta pv".

Colour. Yellow to pale orange in life.

Adult male. Dorsum. ( Fig. 20 ) Body measurements: v2 –h1 196–228, sc2–sc2 110–125; idiosomal length 240– 305, width 140–180. Distances between other setae: v2–v2 52 –60, sc1–sc1 66–77, c1–c1 44–51, c3–c3 148–216, d1–d1 41–44, d1–d 2 22–25, e1– e 1 43–44, e1– e 2 21–23, f1–f 1 24–28, h1–h 1 11–14. Body tapering caudally, striation and setal form similar to that of female; dorsal opisthosoma with mostly transverse striae; with band of more widely–spaced transverse striae posteriad h1; with longitudinal striae laterad c2 and d1–e1; dorsal setae weakly barbed, each with minute distal fork. Setal lengths: v2 39 –46, sc1 37–51, sc2 48–57, c 1 28–37, c2 44–54, c3 56–63, d1 32–38, d2 46–53, e1 33 –40, e2 39 –52, f1 36–40, f2 46–49, h1 33–39, h 2 21–23, h 3 21–23. Setae h3 often inserted ventrally, depending on mounting.

Venter. ( Fig. 21 ) Body finely striate, striae almost entirely transverse with no lobes; all ventral setae thin, smooth: 1a 23–26, 1b 23–26, 1c 36–41, 2b 30–31, 3a 14–15, 3b 26–30, 4a 19–20, 4b 25–28, ag 21–24, g 1 14–17, g 2 12–15, ps 1 12–15, ps 2 12–15. Setae ps1 often inserted dorsally to dorsolaterally ( Figs 20–21 ), depending on mounting.

Gnathosoma . ( Fig. 31 ) Short spinneret (suζ) on palp tarsus slightly smaller than that of female (1.5–1.8 wide, 4 long); single solenidion (4–5) and two eupathidia (Μl ′ 4, Μl" 5). Dorsal femoral seta dPFe modified as short thick peg-like seta, as occurs in males of other genera. Peritreme anastomosing.

Aedeagus. ( Figs 32–37 ) Directed dorsally, strongly sigmoid, thickened with blunt tip. Measurements (see Fig. 32 ): a: 5–7, b: 10–11, c: 5, d: 30.

Legs. ( Figs 22–30 ) Leg striation same as female. Empodia I split into two sets of three proximoventral hairs with middle pair of hairs significantly thickened, uncinate, appearing as a pair of “claws” when viewed dorsally ( Figs 23–25 ) (depending on angle of mounting, empodium I can appear to be uncinate with a dorsal spur, Figs 23– 24 ). Empodia II–IV, similar to female empodia, split into two sets of three proximoventral hairs, with proximal pair of hairs thicker than other two pairs ( Figs 27, 28 ). Tarsus I ( Fig. 22 ) with two distal and adjacent duplex setae (solenidia: proximal ω ′ 30–33, distal ω" 42–44; companion fastigial setae: ft', ft" 6–9), a single, spindle-shaped proximal solenidion (ω" 1 10–11), and three distal eupathidia (p'ζ, p"ζ 17–18; pv'ζ 7–9). Tibia I with three solenidia (φ'Ƌ 6, φ"Ƌ 7 (both spindle-shaped), φ 8–9). Tarsus II ( Fig. 26 ) with one duplex seta (solenidion ω" 29–30; companion seta ft" 5–7), a pair of short spindle-shaped proximal solenidia (ω ′1Ƌ, ω" 1 11–12) and three distal eupathidia (p'ζ, p"ζ 16–17, pv ′ζ 6–7). Tarsus III ( Fig. 29 ) with single proximal solenidion (ω ′ 18–21). Tarsus IV ( Fig. 30 ) with single proximal solenidion (ω ′ 16–19). All leg setae finely barbed. Number of setae on legs I–IV respectively: trochanters 1, 1, 1, 1; femora 10, 7, 2, 2; genua 5, 5, 3, 3; tibiae 11 (3), 5, 5, 5; tarsi 15 (3+3), 13 (3+3), 8 (1+0), 8 (1+0). Leg setation as presented on Figures 22, 26 , 29–30 , with same chaetotaxy as female except for the presence of additional solenidia on certain segments. One specimen with three anomalies: lacking seta v″ on femur I and seta d on tibia II on left-hand side, and with symmetrical addition of two extra solenidia on tarsus I.

Deutonymph. Dorsum. S etal form and body striation similar to adult. Body measurements: v2 –h1 210–230, sc2–sc2 110–135. Distances between setae: c1–c1 46–48, c3–c3 175–200, d1–d1 37–41, d1–d 2 28–31, e1–e1 45–48, e1– e 2 27–29, f1–f 1 22–24, h1–h 1 13–14. Setal lengths: v2 32 –40, sc1 38–43, sc2 40–49, c 1 24–29, c2 42–43, c3 50–57, d 1 28–35, d2 39–47, e 1 28–35, e2 36–45, f 1 31–36, f2 39–44, h1 42–45, h 2 28–31, h 3 26–30.

Venter. Striation similar to adult, except longitudinal–oblique striae from aggenital setae (ag) to setae h2, h3. Setal lengths: 1a 22–24, 1b 22–25, 1c 39–40, 2b 23–30, 2c 41–45, 3a 13–17, 3b 27–38, 4a 17–19, 4b 25–27, ag 20–24, g 1 17–19, ps 1 17–18, ps 2 17–20.

Gnathosoma . Similar to female.

Legs. Leg striation and form of setae similar to female. Number of setae on legs I–IV respectively: trochanters 1, 1, 1, 0; femora 6, 3, 2, 2; genua 5, 5, 3, 2; tibiae 8 (1), 5, 5, 5; tarsi 15 (3+3), 11 (1+3), 8 (1), 7.

Ontogenetic changes in leg setation. Without having a larva or protonymph of E. spinophilus to examine, it was difficult to determine whether the setae we have labelled as pv" on both tarsus I and II are indeed pv" or if in fact they are v"1 and v'1 respectively, which are normally added in the deutonymph. However, by examining different developmental stages of other species, we are confident the setae are pv". Tarsus III should have 9 (1+0) setae (10 in adult) and tarsus IV should have 8 setae (11 in adult) in the deutonymph; however E. spinophilus is missing the same seta on each of these segments, pv", and consequently seta pv" is missing on tarsi III–IV. The absence of setae pv" is unusual, as larval setae are normally present. This seta is also absent in Tuckerellidae , and both primiventrals are absent in Tenuipalpidae and Linotetranidae . For additional comments, see section in female description.

Protonymph and Larva. Unknown.

Differential diagnosis. Few species of Eotetranychus are like E. spinophilus . The species E. thewkei Baker & Tuttle, 1994 shares the short dorsal setae and a reduced leg setal chaetome (e.g. genu III with three setae, tibia II–III with five setae) with E. spinophilus , but has a peritreme terminating in a small bulb, transverse striae on the prodorsum, and much shorter dorsocentral setae c1, d1 and e1. As with the new species, the host of E. thewkei is a grass, Aristida adscensionis (Poaceae) . The only other species of Eotetranychus from Poaceae are E. pomeranzevi ( Reck, 1956) , E. qinlingensis Wang, 1980 and E. roederei Gutierrez, 1967 , none of which share the above mentioned features of E. spinophilus , and all of which are more typical Eotetranychus with long dorsal setae, complete setal leg chaetome and linear peritremes.

Remarks. The tribe of grasses, Triodieae , known as spinifex grasses, is one of the most characteristic of all Australian arid zone plant groups. Spinifex forms a dominant vegetation community known as ‘hummock grassland’ on over 22% of the continent of Australia, with vast tracts of central and north-western Australia dominated by spinifex grasses. Hummock grassland is the most widely distributed biome on the Australian continent (Dickman et al., 2 014), and this group of grasses is of key importance to the ecology of arid and semiarid Australia ( Griffin 1992; Beard et al., 2 013). The new spider mite species E. spinophilus was found in association with four other species of mites ( Eriophyidae , Phytoseiidae , Tydeidae , and a new species of Dolichotetranychus ( Tenuipalpidae )) and a species of thrips ( Thripidae ), suggesting that Australian spinifex grasses host a rich fauna of arthropods.

Etymology. The specific name spinophilus (spine-lover) refers to the exceptionally sharply pointed tips of the leaves of the host plant genus Triodia that make collecting from these plants a memorably painful experience.

Figures

FIGURE 1. Eotetranychus spinophilus sp. nov., female, dorsal idiosoma.

FIGURES 2 – 7. Eotetranychus spinophilus sp. nov. female. (2) mid-ventral region; (3) posterior ventral opisthogaster; (4 – 7) spermatheca variation.

FIGURES 8 – 14. Eotetranychus spinophilus sp. nov. female. (8 – 10) peritreme, different specimens; (11) palp, ventral view; (12) palp, dorsal view; (13) leg I, right side, dorsal to abaxial view; (14) ambulacrum I. Scale bar for ambulacrum = 40 µm.

FIGURES 15 – 19. Eotetranychus spinophilus sp. nov. female. (15) leg II, right side, dorsal view; (16) ambulacrum II; (17) leg III, right side, abaxial view; (18) ambulacrum III; (19) leg IV, right side, abaxial view.

FIGURES 20 – 21. Eotetranychus spinophilus sp. nov. male. (20) dorsal idiosoma; (21) posterior ventral opisthogaster.

FIGURES 22 – 28. Eotetranychus spinophilus sp. nov. male. (22) leg I, right side, dorsal to abaxial view; (23 – 24) empodium I, different specimens and views; (25) ambulacrum I; (26) leg II, dorsal to adaxial view; (27) empodium III; (28) ambulacrum III, different specimen. Scale bar for ambulacra = 20 µm.

FIGURES 29 – 37. Eotetranychus spinophilus sp. nov. male. (29) leg III, left side, dorsal to adaxial view; (30) leg IV, right side, abaxial view; (31) palp, dorsal view; (32 – 34) aedeagus, different aspects of same specimen; (35 – 37) aedeagus, different aspects of another specimen. Scale bar for aedeagi = 100 µm.