Extenuipalpus sagittus ( Meyer, 1993 )

Beard, Jennifer J., Ueckermann, Edward A., Castro, Elizeu B. & Seeman, Owen D., 2024, A revision of the genus Extenuipalpus Reck, 1959 (Trombidiformes: Tetranychoidea: Tenuipalpidae), with description of a new species, Zootaxa 5417 (1), pp. 1-62 : 36-49

Extenuipalpus sagittus ( Meyer, 1993)

( Figs 27–39 )

Tenuipalpus sagittus Meyer, 1993:71 , figs 143–147—original description.

Extenuipalpus sagittus ( Meyer, 1993) — Beard et al. 2016: 14.

Material examined. Paratypes: 2 females, ex species of Restionaceae, Ruiterbos, Outeniqua Pass near Mossel Bay , Western Cape Province, South Africa, 03.viii.1986, S. Neser (X86/192; AcY:92/167; ARC-PHP) . 1 male, 1 deutonymph, 1 larva, ex unidentified Restionaceae, Swellendam , Western Cape Province, South Africa, 30.xii.1991, S. Neser (same collection data as holotype listed in Meyer (1993)) (NF2083; X92/8; AcY:92/166; ARC-PHP) .

Diagnosis. Female. Prodorsal setae sc1 short, obovate, half size of obovate setae sc2; mid-prodorsum with reticulation. Opisthonotal setae c1, d1, e1 minute. Cuticle finely striate on coxal fields I–II. Ventral opisthosoma without small region of colliculate cuticle laterad anterior corners genital flap. Femora IV nude. Genua I–II with two setae (lʹ, lʺ present, d absent). Tibiae II with four setae (d, lʺ, vʹ, vʺ present, lʹ absent). Male. Setae v2 short, oblanceolate, about twice size of small oblanceolate setae sc1. Deutonymph. Setae sc2, c3 oblanceolate; femur II seta d lanceolate. Larva. Dorsal setae sc2 short, h2 flagellate, c3 short simple, e3 short lanceolate.

Description. Adult female. (2 measured). Dorsum. ( Figs 27–29 ) Body measurements: v2–h1 232–257, sc2–sc2 154–158, c3–c3 182–187, f3–f3 95–97. Anterior margin of prodorsum with broad median forked projection forming a central triangular notch 27–30. Prodorsal shield weakly developed, with some fine striae/plicae arching around a region of reticulate cuticle medially; with some fine oblique striae/plicae laterally. Prodorsum somewhat wider than long; setae sc1 and sc2 inserted in almost transverse line anteriorly, slightly posterior to setae v2. Opisthosoma with a small central region of reticulate cuticle, flanked laterally by band of fine longitudinal striae/plicae; lateral cuticle smooth. Dorsal setae of various forms. Prodorsal setae obovate; opisthosomal setae c1, d1, e1 minute; opisthosomal setae on lateral and posterior margins broadly lanceolate. Most dorsal setae inserted on small rounded tubercles. Setal measurements: v2 18–26, sc1 11–12, sc2 19–23, c1 6–8, c3 23–25, d1 5–6, d3 11–15, e1 5 –6, e3 25 –30, f3 30–34, h1 23–28, h2 30–31.

Gnathosoma . ( Fig. 30 ). Details of venter not completely discernible; cuticle appears mostly smooth with fine oblique striae/plicae laterally and some fine transverse striae/plicae posteriorly; infracapitular setae m 12–13. Palp tarsus with solenidion 1, eupathidium 4–5; tibiogenu with 2 setae 8–10, 9–10.

Venter. ( Fig. 30 ). Details of venter not completely discernible; cuticle with various patterns of fine striae/ plicae. With weak, very fine longitudinal striae/plicae between setae 1b–1a, coxae I–II appear smooth but with weak fine transverse striae/plicae between 1b–1c; with mostly transverse striae/plicae centrally between 1a–ag; striae/plicae oblique on anal valves and lateral of genital region. Setae g2 inserted just anterior to g1 on genital flap. All setae short, fine, smooth to finely barbed, except setae 1a elongate, flagellate (difficult to measure full length). Setal measurements: 1a 86–118, 1b 18–20, 1c 15–16, 2b 16–20, 2c 13–17, 3a 10–13, 3b 11–14, 4a 56–86, 4b 12–13, ag 10–12, g1 10–13, g2 12–13, ps2 17–21, ps3 14–15.

Spermathecal apparatus. Not visible.

Legs. ( Fig. 31 ). Setal formulae and chaetotaxy for legs I – IV as for type species, E. quadrisetosus , except fe IV nude (d, ev′ absent), ge I–II with 2 setae (l′, lʺ present; d absent; see Remarks), and ti II with 4 setae (d, lʺ, v′, vʺ present; l′ absent). Tarsi I and II each with one abaxial solenidion ωʺ (ta I 8–9; ta II 7–8), companion seta ftʺ (both 9–10), and one pair eupathidia p′ζ–pʺζ (all 8–9). Seta ft′ inserted on small tubercle. Companion seta ftʺ inserted adjacent and just proximal to ft′. Femora I–III setae d thickened and heavily barbed; seta l′ on femora I–II and genu III thickened and heavily barbed; seta bvʺ on femur II much thicker and more heavily barbed than on femur I; tarsi III–IV with setae tc′–tcʺ inserted on short projections.

Adult male. (1 measured). Dorsum. ( Fig. 32 ). Body measurements: v2–h1 196, sc2–sc2 124, c3–c3 128, f3–f3 62. Anterior margin of prodorsum with broad median forked projection forming a central notch 12. Prodorsum and dorsal opisthosoma mostly smooth with some fine, mostly longitudinal striae/plicae centrally and posteriorly, and with regions of sparse fine punctations; posterior lateral striae/plicae becoming oblique. Dorsal opisthosoma weakly divided into mesonotal region and pygidial region by narrow band of weak transverse striae/plicae; mesonotum with three regions indicated by striae/plicae patterns: central region mostly smooth with setae c1 and d1, flanked by finely punctate regions capturing setae c3 and d3. Pygidial region with some fine longitudinal striae/plicae, distinctly narrower than mesonotal region. Dorsal setae similar in general form to those of female, with prodorsal setae being slightly more acute distally. Most dorsal setae inserted on small rounded tubercles. Setal measurements: v2 13–14, sc1 10–11, sc2 15–16, c1 6–8, c3 17–18, d1 6, d3 11, e1 7, e3 18, h1 15, h2 18–19.

Gnathosoma . ( Fig. 33A ) Ventral cuticle posterad infracapitular setae m 9–10 with fine transverse striae/plicae. Palp tarsus with solenidion 4, eupathidium 5; tibiogenu with 2 setae 8, 9.

Venter. ( Fig. 33A ). Ventral cuticle appears mostly smooth; with some fine longitudinal striae/plicae on anterior lateral margins; with a band of transverse striae/plicae level with coxae IV; scattered mostly oblique striae/plicae posteriorly in genitoanal region. All setae short, fine, smooth to finely barbed, except setae 1a and 4a elongate, flagellate (difficult to measure full length), and ps3 modified as thickened lanceolate accessory genital stylets, inserted on strongly tapered projection from genitoanal region ( Fig. 33A ). Setae g1, g2, ps2 inserted together in paired rows anteriorly flanking genitoanal valves. Setal measurements: 1a 97, 1b 13, 1c 12–13, 2b 16, 2c 13–14, 3a 11–12, 3b 12–13, 4a 72–83, 4b 10–11, ag 9–11, g1 9–10, g2 8–9, ps2 14, ps3 15–16.

Aedeagus. ( Fig. 33B ) Sclerotised, extremely elongate, finely tapering (110), difficult to measure full length, with narrow membranous tube emerging basally.

Legs. ( Fig. 34 ) Setal formulae same as adult female except solenidion ω′ present on ta I–II. Tarsi I and II each with two solenidia (ta I adaxial ω′ 10–11, abaxial ωʺ 10–11; ta II adaxial ω′ 9–10, abaxial ωʺ 10), companion seta ftʺ (ta I 8–9, ta II 8), and one pair eupathidia p′ζ–pʺζ (all 7–8). Seta ft′ inserted on small tubercle. Femora I–III setae d broadly obovate to lanceolate; seta d absent on fe IV.

Deutonymph. (1 measured). Dorsum. ( Fig. 35 ). Body measurements: v2–h1 266, sc2–sc2 140, c3–c3 158, f3–f3 70. Anterior margin of prodorsum with median forked projection forming a central triangular notch 14. Prodorsum with central subrectangular shield indicated by striae/plicae, capturing setae v2, sc1 and two pairs minute pores. Dorsum with a broad band of widely-spaced transverse folds from setae sc2 to level with setae c3 and d1; cuticle posterior to d1–c3 mostly smooth, with a few longitudinal striae/plicae and pair of minute pores laterad e1. Setae v2, sc1, c1, d1, d3, e1 small to minute; other setae obovate to broadly lanceolate (similar in general form to those of female). Setal measurements: v2 5–6, sc1 5–6, sc2 21, c1 5, c3 15–16, d1 4–5, d3 5, e1 3 –4, e3 24 –27, f3 25–27, h1 18–20, h2 25–27.

Gnathosoma . Palp details not discernible.

Venter. ( Fig. 36 ) Ventral cuticle completely finely striate/plicate, with various patterns of fine striae/plicae. All setae short, fine, smooth to finely barbed, except setae 1a and 4a elongate, flagellate (difficult to measure full length). Setal measurements: 1a at least 35, 1b 13, 1c 7–9, 2b 12, 2c 9–10, 3a 9–10, 3b 8–9, 4a 46–47, 4b 7–8, ag 6–7, g1 7, ps2 9, ps3 10.

Legs. ( Fig. 37 ) Setal formulae for legs I – IV the same as the female except tr IV nude. Tarsi I and II each with one abaxial solenidion ωʺ (ta I 7; ta II 6), companion seta ftʺ (both 8), and one pair eupathidia p′ζ–pʺζ (all 6–7). Seta ft′ inserted on small tubercle. Seta bvʺ on femur II much longer and thicker than on femur I; tarsi III–IV with setae tc′–tcʺ inserted on short projections.

Protonymph. Unknown.

Larva. (1 measured). Dorsum. ( Fig. 38 ). Body measurements: v2–h1 174, sc2–sc2 105, c3–c3 107, f3–f3 44. Anterior margin of prodorsum broadly rounded, without projections or notch. Details of sculpturing on dorsal cuticle not discernible, entire dorsum appears smooth. Dorsal setae of various forms, but mostly short to minute; setae e3, f3 and h1 narrowly lanceolate, barbed; setae h2 elongate, flagellate, barbed; remaining setae all short to minute. Setal measurements: v2 5, sc1 5–6, sc2 7–8, c1 4–5, c3 7, d1 3–4, d3 4–5, e1 3 –4, e3 7 –9, f3 14–15, h1 9–10, h2 48.

Gnathosoma . Palp details not discernible.

Venter. Details of ventral cuticle not discernible, cuticle appears to be covered in faint, very fine, mostly transverse striae/plicae. Setal measurements: 1a at least 43, 1b 14, 3a 6–7, ps2 6, ps3 5.

Legs. ( Fig. 39 ). Leg segments with fine striae/plicae. Setal formulae for legs I – III as in E. quadrisetosus except ti II with 4 setae. Tarsi I and II each with one abaxial solenidion ωʺ (both 5–6), companion seta ftʺ (both 6–7), and one pair eupathidia p′ζ–pʺζ (all 6–7). Setae ft′ and ftʺ inserted on small tubercles.

Host. Restionaceae species.

Distribution. South Africa: Western Cape Province.

Remarks. According to Lindquist (1985), the basic pattern of leg setae additions for Tetranychidae larvae on genu I–II is l′, lʺ, v′, vʺ, with no setae being added in the protonymph, seta d being added in the deutonymph, and no setae added in the adult stage. Seta v′ is suppressed on the genua in all tetranychoid families except Tetranychidae (and Linotetranidae keeps v′ on ge I only) ( Lindquist 1985). Seta d is generally added to genua I–II and suppressed on genua III–IV in the deutonymphs of other tetranychoid families (not Tetranychidae ), and according to Lindquist (1985) the only seta added to the genua in the deutonymph stage is seta d. However, patterns in the ontogenetic additions of leg setae in the Tenuipalpidae are a little different, and here the expression of seta lʺ is delayed from the larva to the deutonymph. As in other tenuipalpid taxa, E. quadrisetosus larvae have just one seta (l′) present on genua I–II, while the deutonymph (and adult) has three setae present (l′, lʺ, d), as both setae d and lʺ are added in this stage. Extenuipalpus sagittus is different again in that only seta l′ is added in the deutonymph and seta d remains absent.

Meyer (1993) did not provide any details of the biology or colour of these mites.

Figures

FIGURE 27. Extenuipalpus sagittus, adult female paratype dorsum.

FIGURE 28. Extenuipalpus sagittus, adult female paratype, detail of posterior dorsum, presenting variation in sculpturing.

FIGURE 29. Extenuipalpus sagittus, adult female paratype dorsum. A—photographed using differential interference contrast (DIC), and B—phase contrast.

FIGURE 30. Extenuipalpus sagittus, adult female paratype, detail of posterior venter.

FIGURE 31. Extenuipalpus sagittus, adult female paratype legs I–IV (right side; dorsal aspect); with detail of tarsus I (left side; dorsal and ventral aspects), tarsus II (ventral aspect) and unguinal setae illustrated separately.

FIGURE 32. Extenuipalpus sagittus, adult male paratype, detail of dorsum.

FIGURE 33. Extenuipalpus sagittus, adult male paratype. A—detail of venter; B—detail of aedeagus.

FIGURE 34. Extenuipalpus sagittus, adult male paratype legs I–IV (right side; dorsal aspect); with unguinal setae illustrated separately.

FIGURE 35. Extenuipalpus sagittus, deutonymph paratype, detail of dorsum.

FIGURE 36. Extenuipalpus sagittus, deutonymph paratype, detail of posterior venter.

FIGURE 37. Extenuipalpus sagittus, deutonymph paratype legs I–IV (right side; dorsal aspect); with detail of ventral tip of tarsi I–II, and unguinal setae illustrated separately for tarsi III–IV.

FIGURE 38. Extenuipalpus sagittus, larva paratype, detail of dorsum.

FIGURE 39. Extenuipalpus sagittus, larva paratype legs I–III (right side; dorsal aspect); with tarsi I–II unguinal setae illustrated separately.