Aegyptobia gahnia, Beard & Seeman, 2025

Beard, Jennifer J. & Seeman, Owen D., 2025, A new flat mite genus and five new species (Tetranychoidea: Tenuipalpidae) from native Australian sedges (Cyperaceae), Zootaxa 5637 (1), pp. 1-56 : 9-21

Aegyptobia gahnia sp. nov. Beard & Seeman

( Figs 6–14)

Diagnosis. Adult female: as per genus and Aegyptobia macswaini species group, in addition to: body 2 times longer than wide; prodorsal, paired metanotal and pygidial shields developed; dorsal cuticle pattern of strong fine sulci; anterior margin of prodorsum smoothly rounded; dorsal setae not homogeneous in form with short setae centrally and much longer setae laterally and posteriorly; ventral plate not developed, region membranous; anal plates developed but membranous; ps setae inserted in a weak triangle; ps1–2 equal in length to g1–2, ps3 minute; metapodal plates not developed; trochanters 1-1-1-1 (n.b. v′ on tr I–II, IV; l′ on tr III); femora I–II 4-4; tarsi I–IV 9(1)-9(1)-5-5; femora I–III with seta d inserted dorsally, similar in form to posterior dorsal idiosomal setae; tarsal claws pad-like with a ventrally-directed claw-like structure.

Material examined. Holotype. Female, Australia, Victoria, Ararat-Hall’s Gap Road, approx. 7 km E Hall’s Gap turn off, ex. thatch saw-sedge Gahnia radula (R.Br.) Benth. ( Cyperaceae ), 37°09’13.5” S 142°34’30.5” E, 02.iii.2015, J.J. Beard and C.J. Burwell ( QM). Paratypes. 18 females, 6 males, 2 deutonymphs, 4 protonymphs, 1 larva, same data as holotype ( QM).

Description

Adult female (8 measured).

Dorsum. ( Fig. 6) Body measurements: v2–h1 310–348 [332], sc2–sc2 140–161 [160], c3–c3 164–192 [188], f3–f3 111–122 [117]. Prodorsum with widely spaced longitudinal plicae over most of region, with large central area of smooth cuticle; multiple minute pores visible; anterior margin without projections or notches. Opisthosoma with pair of large, rounded, smooth mesonotal shields between setae c1 and c2; anterior margin opisthosoma with band of finely colliculate cuticle; with longitudinal plicae between c1 setae and laterad mesonotal shields; with broad band of widely spaced transverse sulci from d1 to level with e2; cuticle posterior to e2 much smoother, forming a weak pygidial shield with few longitudinal to oblique plicae; 2 pairs small pores present (mesad d2, posteromesad e2) and multiple minute pores visible. Dorsal setae barbed, variable in length, with setae along posterior margin long, thick, barbed. Setal measurements: v2 8–10 [10], sc1 13–16 [13–15], sc2 21–28 [27–28], c1 13–19 [14], c2 10–13 [12], c3 16–27 [16–19], d1 7–9 [8–9], d2 7–11 [10–11], d3 30–43 [37–38–33], e1 7 –9 [-], e2 8 –11 [10], e3 39 –51 [39–51], f2 10–13 [11], f3 49–62 [54–62], h1 38–46 [44–46], h2 42–62 [57–60].

Infracapitulum. ( Fig. 6) Cuticle on dorsal infracapitulum with fine longitudinal plicae; infracapitular seta m present (10–12) [12]. Palps 5-segmented; palp tarsus small with solenidion (5–6) [5] and two eupathidia (4–5); femur and tibia each with single barbed dorsal seta (9–12) [10–12] and (11–12) [12] respectively.

Venter. ( Fig. 7A ) Ventral cuticle entirely plicate. Anterior margin of prosternal cuticle between 1b–1b finely colliculate to finely rugose with longitudinal wrinkles laterally; cuticle 1b–1a smooth; cuticle 1a–3a finely colliculate with widely spaced transverse sulci, becoming much more strongly colliculate along lateral margin of body; cuticle between 3a and 4a with widely spaced longitudinal sulci (weak to strong); band of widely spaced transverse sulci posterior to 4a becoming small central region of broadly V-shaped to oblique sulci anterior to ag; ag–ag with fine to widely spaced transverse sulci; setae g1 and g2 long, barbed, inserted along posterior margin of mostly smooth oval genital flap; entire pregenital and genital region flanked by strong, widely spaced longitudinal sulci that form corrugate cuticle over most of posterior ventral opisthosoma. Small pore at anterior limit of coxae III ( Fig. 7A , indicated by arrow). Ventral setae 1a, 1b, 2b, 2c, 3a, 4a fine, elongate (often broken and difficult to determine full length); setae g1, g2, ps1, ps2 long, thick, barbed; setae ps3 reduced, short, blunt (can be difficult to see). Setal measurements: 1a 55–80 [-], 1b 22–34 [22–25], 1c 14–16 [14], 2b 38–60 [-], 2c 49–80 [73], 3a 32–56 [32–37], 3b 15–22 [18], 4a 53–78 [78], g1 21–26 [22–25], g2 22–26 [22–23], ps1 19–24 [24], ps2 18–22 [22], ps3 2–3 [3].

Spermathecal apparatus. ( Fig. 7B )An elongate, highly coiled, fine membranous duct terminating in a rounded membranous vesicle.

Legs. ( Fig. 8 ) Setal formulae for legs I – IV: cx 2-2-1-1, tr 1-1-2-1, fe 4-4-2-1, ge 3-3-1-0, ti 4-4-3-3, ta 9(1)- 9(1)-5-5. Leg chaetotaxy: cx I 1b, 1c; cx II 2b, 2c; cx III 3b; cx IV 4b; fe I–II d, l′, v′, bvʺ; fe III d, ev′, fe IV ev′; ge I–II d, l′, lʺ; ti I–II d, l′, v′, vʺ (lʺ absent); ti III–IV d, v′, vʺ; ta I–II ft′, ft″, tc′, tc″, p′ζ, pʺζ, u′, uʺ, ωʺ; ta III–IV ft′, tc′, tcʺ, u′, uʺ. Aberrations: one individual with l′ absent on one tr III, and a different seta absent on each genua II— d and l″. Tarsi I and II each with one abaxial solenidion ωʺ (5–7 [7], 5–6 [5–6], respectively) associated with a short companion seta ftʺ (12–16) [15], (9–13) [11] respectively; pair proral setae p′ζ, pʺζ inserted on small truncate tubercles (all 6–7). Some long, thick, barbed setae on legs segments: trochanter III seta l′ 22–27 [25]; femur I seta d 31–41 [41]; femur II seta d 25–34 [34], bv″ 32–39 [32]; femur III seta d 28–35 [35]; genu III seta d 23–30 [29]; tibiae seta d —ti I 50–56 [56], ti II 19–21 [20], ti III 18–29 [29], ti IV 25–38 [35]. Tectal setae on tarsi distinctly shaped—basal section broad with cluster of small barbs and single large barb approximately half way along seta after which becomes very fine ( Fig. 8 ). The lateral true claws are pad-like with an acute ventrally-directed claw-like structure distally on pad, difficult to see clearly as obscured by the tenent hairs ( Fig. 9B ). The pads of the true claws have a finely toothed ventrolateral margin.

Adult male (6 measured).

Dorsum. ( Fig. 10) Body measurements: v2–h1 201–212, sc2–sc2 134–141, c3–c3 147–162, f3–f3 52–66. Prodorsum with widely spaced longitudinal sulci over most of region, with large central area of smooth cuticle (anteriorly with extremely fine plicae, difficult to see); multiple minute pores visible in sublateral longitudinal row; anterior margin without projections or notches. Opisthosoma with large, transversely rectangular, smooth mesonotal shield-like region between setal pairs c2 and d2, with single pair minute pores in each anterolaterad corner; with longitudinal plicae laterad shield; with broad band of fine transverse sulci from d1 to e1; with smooth shield-like region between e1 and h1; with fine transverse plicae posterior to h1; body terminating in projecting anogenital valves that bear short ps1–2 and modified ps3. Dorsal setae barbed, variable in length, with setae along posterior margin long, thick, barbed. Setal measurements: v2 7–10, sc1 8–12, sc2 10–21, c1 9–16, c2 9–11, c3 14–19, d1 7–10, d2 8–13, d3 13–19, e1 7 –10, e2 7 –12, e3 23 –30, f2 9–14, f3 29–43, h1 21–31, h2 27–36.

Infracapitulum. ( Fig. 10) Cuticle on dorsal infracapitulum with fine longitudinal plicae; infracapitular seta m present (7–8). Palps 5-segmented; palp tarsus small with solenidion (5–6) and two eupathidia (4–5), femur and tibia each with single barbed dorsal seta (7–8) and (10–11) respectively.

Venter. ( Fig. 11A ) Ventral cuticle entirely plicate. Anterior margin of prosternal cuticle between 1b–1b finely granulate with longitudinal plicae; cuticle 1b–1a smooth; cuticle 1a–3a finely colliculate with widely spaced transverse sulci, becoming much more strongly colliculate toward lateral margin of body; cuticle between 3a and 4a with weak fine longitudinal plicae; cuticle posterior to 4a with strong transverse plicae and sulci to genital setae and opening. Setae ps3 modified to form long , thick, blunt accessory genital stylets, inserted distally on short membranous projection flanked by projecting anogenital valves that bear short fine ps1–2 distally. Ventral setae very fine, often difficult to determine full length, especially setae 1a, 2b, 2c, 3a, 4a. Setal measurements: 1a 42–47, 1b 9–10, 1c 8–10, 2b 18–22, 2c 33–58, 3a 29–43, 3b 10–15, 4a 23–48, 4b 11–15, g1 10–12, g2 10–12, ps1 7–9, ps2 7–9, ps3 15–17.

Aedeagus. ( Fig. 11B ) Sclerotised, elongate, narrowly subulate (68–70), with narrow membranous tube emerging from sclerotised section, termination not visible.

Legs. ( Fig. 12 ) Setal formulae and chaetotaxy same as adult female. Tarsi I and II each with only a single solenidion ωʺ (both 8), with an associated companion seta ftʺ (8–10, 6–8 respectively), and pair proral setae p′ζ, pʺζ inserted on small truncate tubercles (all 5–6). The proral setae on ta I–II have a distal elongate nipple. Some long, thick, barbed setae on legs segments: trochanter III seta l′ 12–19; femur I seta d 46–50; femur II seta d 31–42, bv″ 12–16; femur III seta d 22–39; genu III seta d 11–14; tibiae seta d —ti I 36–48, ti II 11–15, ti III 17–35, ti IV 22–37. The lateral true claws are pad-like with a broad ventrally-directed claw-like structure on pad, difficult to see clearly as obscured by the tenent hairs ( Figs 9C–D , 12 ).

Deutonymph (2 measured).

Dorsum. Body measurements: v2–h1 292–301, sc2–sc2 129–134, c3–c3 158, f3–f3 95–111. Prodorsum with widely spaced longitudinal sulci over most of region, with large central area of faintly plicate and granulate cuticle; with transverse plicae between v2 and v2; 2 pairs minute pores visible; anterior margin without projections or notches. Opisthosoma with mostly transverse plicae; with longitudinal plicae laterad c2; cuticle posterior to e1 with arching plicae becoming longitudinal. Setal measurements: v2 7–14, sc1 13–24, sc2 22–29, c1 15–21, c2 12–31, c3 21–33, d1 7–11, d2 8–10, d3 25–27, e1 7 –9, e2 9 –11, e3 31 –42, f2 9–15, f3 33–42, h1 27–30, h2 33–43.

Infracapitulum. Cuticle as in adults; infracapitular setae m (9–12). Palps 5-segmented; palp tarsus with solenidion (5–6) and two eupathidia (both 3–4); femur and tibia each with single dorsal barbed seta (both 9–10).

Venter. Ventral cuticle with narrow band transverse plicae between 1b–1b; with longitudinal plicae between 1b–1a; with transverse plicae 1a–g1 with region of irregular between cx IV–IV; setae ag framed by longitudinal plicae laterally and transverse plicae anteriorly and posteriorly; with band of transverse plicae around ps3 becoming longitudinal to posterior. Setal measurements: 1a 34, 1b 22, 1c 13, 2b -, 2c 28–45, 3a 39–43, 3b 10, 4a 42–44, 4b 11–16, ag 9–10, g1 11–13, ps1 8–9, ps2 7–10, ps3 2.

Legs. Setal formulae and chaetotaxy for legs I – IV same as adult female except tr IV nude, fe I–II with 3 setae (l′ absent). Tarsi I and II each with one abaxial solenidion ωʺ (6 and 5, respectively) with associated barbed companion seta ftʺ (7–11 and 8–10, respectively); pair proral setae p′ζ, pʺζ (both 4–5 on both tarsi). Some long, thick, barbed setae on legs segments: trochanter III seta l′ 18–20; femur I seta d 29–42; femur II seta d 29–38, bv″ 26–32; femur III seta d 25–35; genu III seta d 15–19; tibiae seta d —ti I 41–48, ti II 16–24, ti III 19–27, ti IV 21–25. Ontogenetic setal additions: setae 2b are added to coxae II; v′ added to trochanters I–III; d and l″ added to genua I–II; tc′–tc″ added to tarsus IV.

Protonymph (4 measured).

Dorsum. Body measurements: v2–h1 210–238, sc2–sc2 108–116, c3–c3 141–148, f3–f3 60–71. Prodorsum with fine, weak longitudinal plicae over most of region with granular texture; with large central area smooth cuticle; anterior margin without projections or notches. Opisthosoma with mostly transverse plicae; with small region longitudinal plicae laterad c2; cuticle posterior to e1 with arching plicae. Setal measurements: v2 9–11, sc1 14–18, sc2 20, c1 15–18, c2 13, c3 16–24, d1 7–9, d2 9–11, d3 25, e1 7 –9, e2 9 –13, e3 23 –31, f2 9–12, f3 20–29, h1 17–22, h2 17–27.

Infracapitulum. Infracapitular setae m (7–10). Palps 5-segmented; palp tarsus with solenidion (5–6) and two eupathidia (both 3–4); femur and tibia each with single barbed dorsal setae (7–10 and 8–9, respectively).

Venter. Ventral cuticle with narrow band transverse plicae between 1b–1b; with longitudinal plicae between 1b–1a; with transverse plicae 1a–3a with region of irregular between cx IV–IV; cuticle posterior to cx IV transverse to ps3; setae ag framed by longitudinal plicae laterally and transverse plicae anteriorly and posteriorly. Setal measurements: 1a 35, 1b 10–20, 1c 9–10, 2c 19–27, 3a 14–37, 3b 7–9, ag 4–8, ps1 3–5, ps2 3–6, ps3 4–6.

Legs. Setal formulae for legs I – IV: cx 2-1-1-0, tr 0-0-1-0, fe 3-3-2-1, ge 1-1-1-0, ti 4-4-3-3, ta 9(1)-9(1)-5-3 respectively. Leg chaetotaxy: same as larva except 1c, 2c, 3b added to cx I, II, III respectively; l′ added to tr III; and tc′ added to ta I–II. Tarsi I and II each with one abaxial solenidion ωʺ (5 and 4–5, respectively) with associated companion seta ftʺ (both 5–8), and pair proral setae p′ζ, pʺζ (4–5 on both tarsi). Some long, thick, barbed setae on legs segments: trochanter III seta l′ 11–13; femur I seta d 25–38; femur II seta d 22–26, bv″ 14–18; femur III seta d 19–24; genu III seta d 12–14; tibiae seta d —ti I 30–36, ti II 20–21, ti III 17–21, ti IV 14–21.

Larva (1 measured).

Dorsum. ( Fig. 13 ) Body measurements: v2–e1 158 (v2 –posterior margin 175), sc2–sc2 87, c3–c3 118, f3–f3 36. Prodorsal shield weakly indicated, with fine longitudinal plicae becoming weak centrally; anterior margin smoothly rounded without median notch. Dorsal opisthosoma entirely with transverse plicae and sulci except for small region oblique plicae between c1 and c2. Setae h1, h2, f3 inserted ventrally, with setae f2 and e3 inserted on lateral margin. Setal measurements: v2 7, sc1 11, sc2 8, c1 16–18, c2 -, c3 16, d1 9–10, d2 14, d3 -, e1 -, e2 -, e3 15 –16, f2 13–14, f3 18–19, h1 13–17, h2 14–15.

Infracapitulum. ( Fig. 13 ) Cuticle on dorsal infracapitulum appears smooth; infracapitular seta m absent. Palps 5-segmented; palp tarsus with solenidion (5) and two eupathidia (both 4), femur and tibia each with single barbed dorsal seta (7) and (8) respectively.

Venter. ( Fig. 14 ) Ventral cuticle with narrow band transverse plicae between 1b–1b; with longitudinal plicae between 1b–1a; with transverse plicae 1a–3a; posterior 3a with large region of longitudinal plicae to setae h1 with a small central diamond-shaped region of transverse plicae anterior to setae ps3; with oblique plicae laterad genitoanal region. Setae h1, h2, f3 inserted ventrally, with setae f2 and e3 inserted on lateral margin. Setal measurements: 1a 28, 1b 7–8, 3a 12, ps1 2, ps2 2, ps3 3.

Legs. Setal formulae for legs I – III: cx 1-1-0, tr 0-0-0, fe 3-3-2, ge 1-1-1, ti 4-4-3, ta 7(1)-7(1)-3 respectively. Leg chaetotaxy: cx I 1b; fe I–II d, v′, bvʺ; fe III–IV d, ev′; ge I–II l′; ti I–II d, l′, v′, vʺ (lʺ absent); ti III d, v′, vʺ; ta I–II ft′, ftʺ, p′ζ, pʺζ, u′, uʺ, ωʺ; ta III ft′, u′, uʺ. Tarsi I and II each with one abaxial solenidion ωʺ (both 5) associated with companion seta ftʺ (both 5–7), and pair proral setae p′ζ, pʺζ (all 4). Femur I seta d 13; femur II seta d 11–12, bv″ 7–8; femur III seta d 13. Genu III seta d 9–10. Tibiae seta d —ti I 21–22, ti II 14–15, ti III 15–16.

Colour. These mites were broad, flat and shiny orange in colour when alive.

Host. Thatch saw-sedge, Gahnia radula (R.Br.) Benth. ( Cyperaceae ).

Distribution. This mite is so far known only from Victoria, Australia, where the host plant was growing along the side of the road.

Etymology. This species is named after the genus of its sedge host, Gahnia J.R. & G.Forst, which in turn was named after the Swedish botanist and student of Linnaeus, Dr Henricus Gahn.

Remarks. Aegyptobia gahnia sp. nov., the first species in this genus to be described from Cyperaceae , is an unusual species of Aegyptobia , but less so in the context of the macswaini species group, which includes several members with more elongate bodies with poorly defined dorsal shields, combined with a tendency to associate with host plants in the order Poales .

The macswaini species group bears a close resemblance to the genus Pseudoleptus Bruyant, 1911 , and no single character state separates these two assemblages. However, all Pseudoleptus have acutely-pointed anterior prodorsal projections ( Khanjani et al. 2012) and, as A. gahnia sp. nov. lacks these projections, we exclude this species from Pseudoleptus . Nevertheless, various species distributed within both genera show similarities that may reflect their shared association with Poales . In this respect, the body of A. gahnia sp. nov. is striate, mesonotal shields are apparent, and prodorsal, opisthosomal, and ventral shields are poorly expressed. Additionally, A. gahnia sp. nov. and other members of the macswaini group share the distinct triangular arrangement of the pseudanal setae with species of Pseudoleptus , although the triangle is not as exaggerated in the macswaini group with ps2 not always as lateral as that found in Pseudoleptus .

The unusual ventral claw-like structures on the pad-like empodia could be interpreted as an autapomorphy of A. gahnia sp. nov. However, re-examination of a paratype of A. bromi Khanjani, Khanjani & Seeman shows that this species has a similar claw-like structure ( Fig. 9A ). As the holotype of A. mcswaini does not have this structure (pers. comm. Aline Tassi), it is unknown how widespread it is within the species group. Closer examination of other Aegyptobia and Pseudoleptus with pad-like claws is needed to elucidate the prevalence of this unusual character state. Within the macswaini species group, A. gahnia sp. nov. is possibly unique by having minute setae ps3, but ventral details are not provided in several descriptions, restricting diagnostics to the dorsum alone. In this sense, A. gahnia sp. nov. is similar to A. torreyi Baker & Tuttle , in being the only species of the macswaini species group with distinctly long opisthomarginal setae that contrast with very short opisthosomal sublateral and central setae. The species are easily distinguished by the absence of a distinct metanotal region in A. torreyi . We note that the contrasting opisthosomal setae are also a feature of many Pseudoleptus species, further indicating a close relationship between A. gahnia sp. nov. and Pseudoleptus .

The minute pair of ps3 setae in Aegyptobia gahnia sp. nov. also raises the possibility of a close relationship with Phytoptipalpus , as this genus is separated from Aegyptobia by only the loss of a single ps seta. However, members of Phytoptipalpus all have uncinate claws ( Khanjani et al. 2012), suggesting a closer relationship with the tragardhi species group of Aegyptobia . Nevertheless, it may be pertinent to re-examine species of Phytoptipalpus for similar reduced setae, which may be concealed beneath the genital flap.

Figures

FIGURE 7. Aegyptobia gahnia sp. nov. Beard & Seeman adult female—A. posterior venter (arrow on anterior coxa III is indicating a pore); B. spermatheca.

FIGURE 8. Aegyptobia gahnia sp. nov. Beard & Seeman adult female legs (right side), with detail of ventral aspect of tarsi I–II.

FIGURE 9. Detail of ventral claw-like projection on true claws of the pretarsus (indicated by arrows)—A. Aegyptobia bromi Khanjani, Khanjani & Seeman adult female; B. Aegyptobia gahnia sp. nov. Beard & Seeman adult female; C.–D. Aegyptobia gahnia sp. nov. Beard & Seeman adult male.

FIGURE 11. Aegyptobia gahnia sp. nov. Beard & Seeman adult male—A. posterior venter (n.b. anogenital valves have been spread apart to reveal ps3); B. aedeagus.

FIGURE 12. Aegyptobia gahnia sp. nov. Beard & Seeman adult male—legs I–III (right side), with detail of both aspects of the tarsi, and detail of the dorsal and lateral aspects of the ventral claw-like projection on the true claws of the pretarsus.

FIGURE 13. Aegyptobia gahnia sp. nov. Beard & Seeman larva dorsum, with detail of palps.

FIGURE 14. Aegyptobia gahnia sp. nov. Beard & Seeman larva, ventral aspect.