Abrolophus ripicola
Creators: name: Seeman, Owen D.
name: Beard, Jennifer J.
name: Fan, Qing-Hai
name: Otto, Jürgen C.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Erythraeidae
Abrolophus
Abrolophus ripicola

description: Abrolophus ripicola (Womersley, 1934)
Figures 7–17, 19–23
Diagnosis (adults). Prodorsal sclerite poorly developed, reduced to smooth cuticle around crista, capturing at most one pair of setae on anterolateral margins. Naso usually with 2, sometimes 1 or 3 setae. Dorsal setae only slightly thickened, barbs small. Female genital opening with a single line of setae on each flap, each line comprising no more than 18 setae. Palp slender, femur and tibia each about twice as long as wide; all palp setae smooth and unspecialised. Coxal apodemes III-IV fused to form a deep half-loop. Tibiae II-III with 23–24 tactile setae, all slender with few or no barbs, no setae obviously different from others (i.e. no anteroventral setae thicker, shorter and heavily barbed). Nymphs: Similar, except lacking genitalia (small genital sclerite absent), naso with 1–2 setae and tibiae II-III with 8–10 tactile setae.
Type material examined. Seven syntypes on six slides, as follows. South Australia: 5 females, 1 male, 1 nymph, Hindmarsh River, Victor Harbour, January 1934, H. Womersley (SAMA J24618–23).
Intercepted material examined, matching A. ripicola syntypes. 15 females, as follows. New Zealand: 2 females, ex kiwifruit, 13 May 1998 (Q7870). 1 female, ex kiwifruit, 3 Jul 2000 (QMB; Q18988). 1 female, ex kiwifruit, 12 Sep 2001 (Q23482). 1 female, ex kiwifruit, 7 Jun 2004 (Q105091, 17690QA). 1 female, ex kiwifruit, 12 Jul 2004 (BIN: 104159, Q105405, 18221QA). 1 female, ex kiwifruit, 31 May 2006, AQIS NSW (QMB; N114385, # 033632 NA)—specimen drawn. 1 female, ex kiwifruit, 22 Sep 2018 (QMB; N187595) —gnathosoma drawn. 1 female, ex kiwifruit, 14 Dec 2004, AQIS NSW (N108867, #024343NA). 1 female, ex kiwifruit, 16 Jun 2006, AQIS NSW (N114522, #033860NA). 1 female, ex kiwifruit, 30 Jun 2006, AQIS NSW (N114674, #034136NA). 1 female, ex live cacti, 23 Mar 2007, AQIS NSW (N117435, #038814NA). 1 female, ex kiwifruit, 4 Jul 2011, AQIS NSW (N137572, #070233NA). 1 female, ex kiwifruit, 10 Jun 2015 (N162437). 1 female, ex kiwifruit, 1 May 2019 (QMB; N193640) [smaller specimen but closest to syntypes; Table 3]; 1 female, ex kiwifruit, 11 Jun 2019 (N194782).
5 nymphs, as follows. New Zealand: 1 nymph, ex kiwifruit, 29 May 2002 (N44822). 1 nymph, ex kiwifruit, 8 Jun 2010, BSG CER (N130888, #060132NA). 1 nymph, ex kiwifruit, 30 Jul 2012 (QMB; N144023, # 080430 NA). 1 nymph, ex kiwifruit, 22 Sep 2018 (N187595). 1 nymph, ex kiwifruit, 8 May 2019 (QMB; N193892).
Australian material examined, matching A. ripicola syntypes. 4 females, 1 male, 4 nymphs, as follows. Queensland: Mundubbera region (locality not certain), fresh citrus, 10 Jul 2015 (BIN: 237194, Q148417, 79838QA). South Australia: 1 female, Myponga, 1 Jan 1947 (remounted 8 Dec 1988), R.V. Southcott, under bark Eucalyptus sp. (SAM J25796 *). 1 female, Waterfall Gulley [sic], 25 Feb 1951, R.V. Southcott (SAM J25839 *). 1 female, Heywood Park, 25 Dec 1951 (SAM J25834). 3 nymphs, Loveday, South Australia, 7–8 Sep 1985, By B. f. 22 Sep 1985, R.V. Southcott (SAM J25785, J25793, J25795). New South Wales: 1 female, 1 male, Armidale, 3 Oct 1960, H. Spencer (remounted 25 Jan 1996) (SAM J25778 - J25779 *). Victoria: 1 nymph, Dartmoor, May 1952, A.N.C. (SAM J25836). * = measured, other specimens checked for conspecificity.
New Zealand material examined, matching A. ripicola syntypes. Auckland: 2 females, 1 deutonymph, Pukekohe, 4 Aug 2021, S. George, Persea americana leaves (PANZ T21 _01393). 1 female, St Johns, 20 Mar 2024, Q.-H. Fan, Leptospermum scoparium leaves (PANZ no accession number). 4 females, St Johns, 10 Apr 2024, Q.-H. Fan, Muehlenbeckia sp. leaves (PANZ T24 _01496).
Intercepted material examined, close to A. ripicola syntypes. New Zealand: 1 nymph, BIN:94135, Q108175, 22630QA, 22.vi.2005, kiwifruit, fresh [poor specimen, more elongate palps and tarsus I].
Other material examined (SAM), close to A. ripicola syntypes. New South Wales: 1 female, ex mandarins, Sydney, BSG CER [possibly much smaller female of A. ripicola]. Queensland: 1 female, Cairns, Queensland, 31 Dec 1943 (ACA 1352, J25787) [poor specimen, ASens absent—not even bases present; possibly another species but is close to A. ripicola]. 1 male, Cairns, Queensland, 29 Feb 1943 (ACA 1555, J25792) [poor specimen with many key features distorted, but crista has a different form, becoming significantly broader posteriorly; dorsal setae shorter and seem more barbed]. 1 male, Dead Man’s Gully, Cairns, Queensland, 2 Jan 1944 (J25835) [similar to J25792]. 1 female, Wondecla, 15 Aug 1943, R.V. Southcott (J25832) [similar to J25792]. South Australia: 1 nymph, 4 miles SW of American River, Kangaroo Island, South Australia, 21 Sep 1959, H.M. Cooper, on tableland in tea-tree scrub [poor specimen, possibly A. ripicola but legs and palps obscured; prodorsal measurements similar]. Papua New Guinea: 1 nymph, Babiang, 14 Dec 1944 (J25838); 1 female, Suain, 28 Jan 1945 [both another species, intermediate between A. ripicola and A. novaeguinensis]. South Africa: 1 female, Potchefstroom, ex moist litter and grass, 28 Apr 1982, D.E. Johnston [J24239] [another species, similar to A. ripicola; Fig. 19B, 20B, 21B, 23B].
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Description.
Nymph (n= 1 syntype, n=5 intercepted non-types). Standard measurements in Table 4.
Figures 7–9, 16
Similar to female (see below).
Dorsum (Fig. 7). Scutum similar to M. brevipes, reduced to a lightly sclerotised region poorly defined by limits of prodorsal striation, with one pair of setae on anterolateral margins or just off margin. Naso with 2 setae (one specimen with one seta), several punctations between naso seta and ASens. Crista well-defined, similar to adult, anteriorly divided around and between bases of ASens but not extending far beyond ASens, posterior extension terminates beyond bases of PSens with short branches/extensions along distal margin. ASens and PSens slender with few barbs in distal half; cuticle anterior to and between PSens with few punctations. Dorsal setation similar to adult but with fewer setae.
Venter. Intercoxal region with numerous setae, finer and longer than dorsal setae; coxae I with 7–9 setae (including 2–3 anterolateral setae); coxae II with 1–2 setae, posterior margins poorly defined, sometimes capturing additional posterolateral seta; coxae III with 2 setae (incl. 1 anterolateral), posterior margins poorly defined; coxae IV with 1–2 setae (incl. 0–1 anterolateral), posterior margin of coxa IV poorly defined. Apodemes I–II broad, not fused together; apodemes III and IV fused in a deep half-loop. Genital opening absent. Anal opening with 3/2 setae (incl. syntype) or 2/2 setae.
Gnathosoma (Fig. 8). Partially obscured in syntype; with 2 pairs of pre-palpal setae; 7 pairs of larger subcapitular setae and three pairs of oral setae. Palp femur and genu more elongate in syntype than intercepted non-types (Table 4). Setal count, trochanter to tarsus, taken from non-types: 1-8-7-7+claw-17. Tarsal phaneres comprising 6 smooth, thin tactile setae and 11 thickened, blunt eupathid-like setae.
Legs. Similar to female but with fewer setae; same as M. brevipes larva plus additional setae, and most but not all trochantal–tibial setae could be designated with standard notation (e.g. Fig. 9). For example, additions for leg III as follows: d to trochanter; v’1, v’’2, and “x” to genu and tibia (x in a position between l’ and v’); tarsi with 5 additional setae. Setal counts for selected segments: femur II 4/4, femur III 4/4; genu II 6-8+1σ+1κ; tibia II 8-10+1 or 2ϕ (usually 2ϕ); genu III 6-8+1σ; tibia III 8-9+1ϕ. Variable setae are among those added, often asymmetrically. Specialised setae as follows. Leg I: Ge 1-2σ (usually 1σ); Ti 5φ+1κ; Ta with ca. 9 ω, 14 ζ. Leg II: Ge 1σ+1κ; Ti 1-2ϕ (variable); Ta 2ω, 3ζ. Leg III: Ge 1σ; Ti 1ϕ; Ta 1ζ. Leg IV: Ge 2σ; Ti 0-1ϕ (variable); Ta 1ζ. Ventral tarsal setae becoming more pilose towards distal end of tarsus. Tarsus II minute companion seta z absent.
Female (n= 5 syntypes; other specimens compared below and in standard measurements presented in Table 3).
Figures 10–15, 17, 19–23
Dorsum (Figs 10A, 10C, 15, 17A–B, 21A, 22A, 23A). Scutum reduced to a lightly sclerotised region poorly defined by limits of prodorsal striation, bearing one pair of setae on anterolateral margins. Naso with 1–2 setae (2–3 setae in other material), punctate between naso setae and ASens. Crista well-defined, anteriorly divided around and between bases of ASens but not extending far beyond ASens, posterior extension terminates beyond PSens with short distal branches. ASens and PSens slender with few barbs; transparent region between bases of PSens punctate. Prodorsal setae slender, with few small barbs, giving setae a roughened appearance, setae becoming slightly thicker posteriorly. Opisthodorsum with numerous setae (Fig 23A), similar to prodorsal setae, becoming slightly longer posteriorly.
Venter (Figs 11A, 19A). Intercoxal region with numerous setae, finer and longer than dorsal setae, becoming fine and smooth laterad genital region; coxae I with 8 setae and anterolateral cluster of 4 setae; coxae II with 5–6 setae; coxae III with 2 coxal setae and anterolateral cluster of 2–3 setae; coxae IV with 2–3 coxal setae and an anterolateral cluster of 2–3 setae. Apodemes I–II broad, not fused together; apodemes III and IV fine, fused to form a deep half-loop; posterior margin of coxa IV not well-defined. Genital opening with single row of setae, clearly visible in one syntype, symmetrical, with 16/18 setae on each flap (non-types: 14–18 setae, often asymmetrical, left side/right side 17/15, 14/15, 15/14, 17/16). Anal opening with 3/3 and 4/4 setae in two syntypes with visible anal flaps (non-types: 3/3 setae in five specimens, asymmetries 2/3, 2/4, 3/4, 3/4). All setae smooth, slender.
Gnathosoma (Figs 12, 20A). All setae fine, smooth, with four pairs of pre-papal setae; distal subcapitulum with five pairs of long, lateral setae and 6–7 pairs of shorter medial and apical setae. Palp femur and genu elongate, more so in syntypes (ratio L/W = 2.17–2.58, 1.93–2.32, respectively) than intercepted specimens (1.56–2.21, 1.49–1.85, respectively); palp tibia slightly longer than wide, palp tarsus about twice as long as wide. All setae fine, smooth; tibial claw about as long as tarsus. Setal count, trochanter to tarsus: Tr 1–2 (2 as asymmetry); Fe 13–14 (usually 13); Ge 10–15; Ti 7–10+claw; Ta 18–19. Number of tactile setae on genu and tibia highly variable, syntypes exhibit maximum range. Tarsal phaneres comprising 6 smooth, thin tactile setae and 12–13 thickened, blunt eupathid-like setae. Cheliceral shafts linear, their proximal ends forming a narrow arch.
Legs (Figs 13, 14B, 15, 17A). All legs shorter than body, legs I and IV longest, with leg I slightly longer than leg IV. Tarsus I about twice as long as high, with numerous fine setae proximally, tending to blunt sensory setae distally and ventrally, with pair of barbed setae apically. Tibia I subequal length to tarsus I. Tibiae II-IV with all setae slender, smooth, none obviously thicker than others. Pretarsi lacking empodia. Specialised setae as follows. Leg I: Ge 1–2σ (usually 1σ); Ti 5 or 6ϕ +1κ; Ta with ca. 15–20 ω, 40–55 ζ. Leg II: Ge 2σ+1κ; Ti 3ϕ; Ta 2ω, 4ζ. Leg III: Ge 2σ; Ti 2ϕ; Ta 3ζ. Leg IV: Ge 2σ; Ti 1-2ϕ (usually 2ϕ); Ta l 3 ξ. Ventral tarsal setae becoming more pilose towards distal end of tarsus. Tarsus II eupathidia positioned as ventrodistal pair, ventromedial, and dorsal tcξ′ (minute z absent); tarsus III eupathidia positioned ventrodistally, ventromedially, and dorsally tcξ′; tarsus IV eupathidia positioned as dorsal pair (tcξ) and ventromedial.
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Male (n= 1 syntype, n=1 non-type). Standard measurements in Table 4.
Figs 10B, 11B.
Similar to female except: naso with 1 seta (2 setae in Armidale specimen), with 1 medial ASens (syntype aberration) or 2 ASens (Armidale); crista Y-shaped anteriorly, lacking medial sclerotisation between bases of ASens, sclerotised between bases of PSens posteriorly, with punctations around bases of Psens. Genitalia with 16/15 setae on each side (20/21 setae in Armidale specimen). Internal genitalia with 13 pairs of setae.
Remarks.
Comparison of A. ripicola with original description. The description and syntype specimens match in the few measurements provided by Womersley (1934) but differ in the number of setae on the naso. Womersley (1934) drew four setae on the naso, but the syntype females have 1–2 setae. The nymph and male syntypes have one seta on the naso. The syntype male is highly unusual in having one anterior sensillum (ASens, Fig. 10B), suggestive of a developmental anomaly.
Comparison of A. ripicola syntypes with Abrolophus zelandicus (Luxton, 1989). Luxton (1989) considered A. zelandicus and A. ripicola as the two most closely related species. The sole diagnostic character separating the species was the number of setae on the naso (2–3 instead of 4). As noted above, Womersley’s description was wrong, and adult females of A. ripicola and A. zelandicus usually express 2–3 setae on the naso (Table 3). Thus, A. zelandicus could be a junior synonym of A. ripicola. To test this hypothesis, we examined the type material of A. zelandicus.
The question of synonymy lies with the holotype and its comparison with the A. ripicola syntype male. In this regard, the male of A. zelandicus is clearly distinguishable. Despite being just a little larger in body size (764 versus 620), numerous measurements are considerably larger, such as length of the anterior sensilli (ASens, 71 versus 46), distance between sensilli (ISD 132 versus 78), and length of the palp femur (121 versus 77) (Table 4; Fig. 24). Therefore, we consider A. zelandicus and A. ripicola as separate species.
Comparison of A. ripicola syntypes with intercepted material. The iterative process revealed just two related features differing between the syntypes and the intercepted material: the syntypes have more elongate palp femora and palp genua. These differences are due to the palp segments being thinner, as they are of a similar length in both sets of specimens. This difference may be real but some syntype specimens show signs of compression and collapse of these segments, suggestive of distortion, thus limiting their power. Without other characters, we do not treat these differences as diagnostic.
The syntypes were generally smaller than the intercepted material (Figs 17A, B), with their body lengths 680– 740 compared with 705–1000, although all but two specimens were 800–900 (one 750, one 1000).
Comparison of A. ripicola syntypes with new material from New Zealand. The Plant Health & Environment Laboratory, Auckland, New Zealand (PANZ) holds eight specimens (seven adults and one deutonymph) that we regard as A. ripicola (Table 3; Fig. 25). Taken collectively with the intercepted material, these specimens have no important differences compared with the syntype series. Most notably, the palpal differences noted above for the intercepted specimens are absent in these specimens.
Comparison of A. ripicola syntypes with other Australian material matching syntypes. The male from Armidale has 21 pairs of genital setae and has longer leg segments, but, as it was collected with a female that strongly matches A. ripicola, we consider it conspecific.
The female from Heywood Park has 20 pairs of genital setae and four pairs of anal setae but is otherwise similar.
description: Published as part of Seeman, Owen D., Beard, Jennifer J., Fan, Qing-Hai & Otto, Jürgen C., 2024, Abrolophus from Australasia, and the mysterious Mypongia (Trombidiformes: Parasitengona: Erythraeidae), pp. 151-189 in Zootaxa 5519 (2) on pages 160-177, DOI: 10.11646/zootaxa.5519.2.1, http://zenodo.org/record/13915687