Morphological ontogeny of Galumna flagellata Willmann (Acari: Oribatida: Galumnidae)

Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=taca20 International Journal of Acarology ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/taca20 Morphological ontogeny of Galumna flagellata Willmann (Acari: Oribatida: Galumnidae) Anna Seniczak, Stanisław Seniczak, Sofía Rodríguez-Fernández & Emilia Fernandez Ondoño To cite this article: Anna Seniczak, Stanisław Seniczak, Sofía Rodríguez-Fernández & Emilia Fernandez Ondoño (2021): Morphological ontogeny of Galumna�flagellata Willmann (Acari: Oribatida: Galumnidae), International Journal of Acarology, DOI: 10.1080/01647954.2021.1880478 To link to this article: https://doi.org/10.1080/01647954.2021.1880478 © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. Published online: 24 Feb 2021. Submit your article to this journal Article views: 89 View related articles View Crossmark data Morphological ontogeny of Galumna flagellata Willmann (Acari: Oribatida: Galumnidae) Anna Seniczak a , Stanisław Seniczak b , Sofía Rodríguez-Fernández c and Emilia Fernandez Ondoño c a Department of Natural History, University Museum of Bergen, University of Bergen, Bergen, Norway; b Department of Evolutionary Biology, Kazimierz Wielki University, Bydgoszcz, Poland; c Department of Soil Science and Agricultural Chemistry Faculty of Sciences, University of Granada, Spain ABSTRACT The morphological ontogeny of Galumna flagellata Willmann, 1925 is described and illustrated. The juveniles of this species are light brown, with prodorsal setae of medium size or long and barbed, and bothridial seta clavate. The larva has 12 pairs of gastronotal setae, most of the medium size and barbed, of which seven (d-, l-series, h 1 ) are located on gastronotal shield, nymphs have 15 pairs, mostly short setae, of which 10 (d-, l-, h-series, p 1 ) are located on the gastronotal shield, setae of c-series are inserted on individual sclerites. In all juveniles, the typical galumnid humeral organ is absent, but a porose area is present in this location, which is unique in Galumna. ARTICLE HISTORY Received 13 October 2020 Accepted 21 December 2020 Published online 24 February 2021 KEYWORDS Oribatid mites; juveniles; individual sclerites; leg setation; stage structure Introduction Galumna Heyden, 1826 sensu stricto is a large subgenus that comprises 198 species and seven subspecies, from which 22 are considered species inquirendae (Subías 2004). The diagnosis of Galumna has recently been given by Ermilov and Klimov (2017), with the main diagnostic characters as follows: body surface usually without strongly developed sculpture or ornamentation, sexual dimorphism in prodorsum and notogaster absent, lamellar and sublamellar lines present, rostral seta inserted close to end of the lamellar line, medial to lamellar lines or distanced from them, and lamellar seta inserted lateral to the lamellar line. Pteromorphs bilobed, partially reticulate, notogaster with 10 or 11 pairs of alveoli or microsetae, with one pair on pteromorphs, porose area Aa singular or divided into two parts, median pore absent or present, singular or subdivided. Leg tarsi tridactylous, leg setae not modified. Diagnosis of subgenus Galumna sensu stricto is the following: notogaster with porose areas, adanal lyrifissures located close and lateral to the anal aperture (Ermilov and Klimov 2017). The morphology of juveniles of Galumna species has rarely been studied. Based on the catalogue of oribatid juveniles by Norton and Ermilov (2014) and paper by Ermilov et al. (2017b), all instars of three Galumna species and one subspecies are known, which constitute nearly 2% of all species of this genus. Some of these studies, such as Haq and Adolph (1981) (G. flabellifera orientalis Aoki, 1966), Sengbusch (1954) [G. ithacensis (Jacot, 1929)], Woodring (1965) [G. parva Woodring (1965), G. louisianae (Jacot, 1929)], only investigated the ecological and biological aspects of juveniles such as development time, cultivating and feeding behaviour, while the described morphology is very general and insufficient for comparisons. Therefore, the morphological ontogeny of all instars of the following species is known: Galumna alata (Hermann, 1804), G. curvifamulus Ermilov et al. (2017a), and G. zachvatkini Grishina (1982) (Grishina 1982; Seniczak et al. 2012; Ermilov et al. 2017b). The juvenile stages of G. elimata (C.L. Koch, 1841), G. obvia (Berlese, 1914) and G. tarsipennata Oudemans, 1914 are partially known (Norton and Ermilov 2014). The morphological ontogeny of G. flagellata has not been investigated. The aim of this paper is to describe and illustrate the morphological ontogeny of G. flagellata, and compare it with that of congeners. Material and methods The juveniles and adults of G. flagellata used in this study for morphological investigation were collected on 30 December 2018 by S. Rodríguez-Fernández during the litterbag experiment carried out in the part of the Science’s Park of Granada, Biodomo, Spain (37° 9′45.28″N, 3°36′22.13″W, 656 m a. s. l.). This park was created in 2016, with controlled climate conditions (26°C and a high level of air moisture), tropical vegetation and soil substrate composed of 50% pine bark and 50% blond peat (renewed periodically). Twenty four litterbags of the size of 20 × 15 cm, made of nylon mosquito net with 2 mm mesh, were filled with 300 cm 3 of dry and crushed prunings of common lantana (Lantana camara L.) (12 litterbags) and with mango (Mangifera indica L.) prunings (12 litterbags), and placed on the soil in Biodomo on 26 November 2018. In order to study the ecology of G. flagellata, samples with common lantana prunings and mango prunings were collected during four sampling events between the end of December 2018 to the end of May 2019 (i.e., after one, two, three and six months from the start of the experiment), in three replications and were extracted in Tullgren funnels during eight days. In these samples, G. flagellata was the only member of Galumnidae, and therefore the assumption is made that the juveniles belong to this species. We investigated the density and stage structure of the mites, and based on 50 randomly selected adults, the sex ratio, number of gravid females and carried eggs, and body length and width in µm. We measured a total body length (tip of the rostrum to the posterior edge of notogaster) in lateral aspect and body width (widest part of notogaster without pteromorphs) in dorsal aspect, and size of anal and genital openings and setae perpendicularly to their length. The illustrations of instars are limited to the body regions of mites that show substantial differences between instars, including the dorsal, lateral aspect and some leg segments of the larva, tritonymph and adult, and ventral regions of all instars. The palp and chelicera of the adult are also illustrated. Illustrations were prepared from individuals mounted temporarily in lactic acid. In the text and figures we used the following abbreviations: rostral (ro), lamellar (le), interlamellar (in) and exobothridial (ex) setae, lamella (La), sublamella (Sub), bothridium (bo), bothridial seta (bs), dorsophragma (D), pleurophragma (Pl), sejugal porose area (Ad) notogastral or gastronotal setae or alveoli (c-, d-, l-, h-, p-series), porose areas (Aa, A1, A2, A3), lyrifissures or cupules (ia, im, ip, CONTACT Anna Seniczak [email protected] Department of Natural History, University Museum of Bergen, University of Bergen, Bergen, Norway. INTERNATIONAL JOURNAL OF ACAROLOGY https://doi.org/10.1080/01647954.2021.1880478 © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. Published online 24 Feb 2021 Figure 1. Galumna flagellata, female, a – dorsal aspect, scale bar 50 μm; b – shape of seta in (enlarged); c – shape of porose are A3 in another individual. 2A. SENICZAK ET AL. Figure 2. Galumna flagellata, female, ventral aspect, legs partially drawn, scale bar 50 μm. INTERNATIONAL JOURNAL OF ACAROLOGY 3 ih, ips, iad), opisthonotal gland opening (gla), pedotectum (Pd), pteromorph (Ptm), discidium (Dis), median pore (mp), postanal porose area (Ap), circumpedal carina (cp), subcapitular setae (a, m, h), cheliceral setae (cha, chb), palp setae (sup, inf, l, d, cm, acm, it, vt, ul, su) and solenidion ω, epimeral setae (1a, 2a, 3a, 3b, 4a–c), adanal and anal setae (ad-, an-series), aggenital seta (ag), leg solenidia (σ, φ, ω), famulus (ε) and setae (bv, ev, d, l, ft, tc, it, p, u, a, s, pv, pl, v). The terminology used follows that of Grandjean (1949, 1953) and Norton and Behan-Pelletier (2009). The species nomenclature follows Subías (2004, updated 2020). For scanning electron microscopy (SEM), the mites were airdried and coated with Au/Pd in a Polaron SC502, sputter coater and placed on Al-stubs with double-sided sticky carbontape. Observations and micrographs were made with a ZEISS Supra 55VP scanning electron microscope. Galumna flagellata Willmann, 1925 Diagnosis Adults dark brown, of medium size (462–540), without sexual dimorphism, and with characters of Galumna. Rostrum rounded, rostral setae distanced from lamellar lines. Bothridial seta fusiform, with long, narrow, barbed head. Dorsosejugal suture and postanal porose area present. Ten pairs of setal alveoli, four pairs of porose areas and median pore present on notogaster, adanal lyrifissures located close to the medial part of the anal opening. Juveniles light brown, prodorsal setae of medium size or long and barbed, bothridial seta clavate. Larva with 12 pairs of gastronotal setae, most of the medium size and barbed, d-, l-series and h 1 located on gastronotal shield, nymphs with 15 pairs, most short, d-, l-, h-series and p 1 located on gastronotal shield, setae of c-series inserted on individual sclerites. In all juveniles, typical galumnid humeral organ absent, but porose area present in this location, which is unique in Galumna. Morphology of adult Adult (Figure 1–7) similar to that described by Willmann (1925), but see Remarks. Mean length (and range) of females 516.2 ± 13.6 (494–- 540, n = 45) and males 481.0 ± 22.5 (462–520, n = 5), mean width (and range) of females 362.1 ± 21.9 (325–388) and males 364.0 ± 29.1 (312–377). Notogastral setae alveolar (10 pairs, including c 2 on pteromorph), porose area Aa larger (mean 36 × 22) than other porose areas (17 x 12), postanal porose area elongated (Figure 1–4a). Hypostomal setae short, h and m slightly longer than a (Figure 2). Cheliceral setae cha longer and thicker than chb, both barbed (Figure 4c), most palp setae finely barbed (Figure 4d, 7d), formula of palp setae 0–2–1–3–9(1). Leg femora relatively slim, most leg setae barbed, setae pv on all tarsi with longer barbs than others (Figure 5, 6b, 7a). Solenidia ω 1 and ω 2 on tarsus I of similar length, seta ft” short (Figure 5a, 6b–d). Formulae of leg setae [trochanter to tarsus (+ solenidia)]: I – 1–4–3(1)–4(2)–20(2); II – 1–4–3(1)–4(1)–15(2); III – 2–3–1(1)–3(1)–15; IV – 1–2–2–3(1)–12. Leg tarsi heterotridactylous. Remarks. The adults investigated herein are smaller than those investigated by Willmann (1925) – length 550–600, width 330 and Weigmann (2006) – length 550–610, sexually not separated. In our individuals, porose areas Aa and A2 are widely more separated than in Willmann (1925), but similar as in Weigmann (2006). The shape and distribution of prodorsal setae in our specimens are generally similar as in figures presented by these authors. Figure 3. Galumna flagellata, adult, posterior aspect, scale bar 50 μm. 4A. SENICZAK ET AL. Description of juveniles Larva egg-shaped in dorsal view (Figure 8, 9a), light brown. Prodorsum subtriangular, prodorsal setae of medium size (in, ex) or long (ro, le, Table 1) and barbed. Mutual distance between setal pair le nearly twice longer than between pair ro, and distance between setal pair in nearly three times longer than between pair ro; pair le inserted approximately midway between pairs ro and in. Opening of bothridium rounded, with anteromedial ridge, connecting bothridium with the insertion of seta in, and posterolateral ridge, connecting bothridium with the insertion of seta ex; bothridial seta clavate, with barbed head. Gastronotum of the larva (Figure 8, 10a, 11a) with 12 pairs of setae, including h 3 inserted lateral to the medial part of anal valves; most of the medium size and barbed, except for minute h 3 . Setae of c-series on individual microsclerites, length increasing from c 1 to c 3 (Table 1), all barbed. Gastronotal shield with seven pairs of setae (d-, l-series, h 1 ), setae h 2 and h 3 on unsclerotized integument. Small porose areas present, Aa anterior to seta la, A1 anterior to seta lm, and A2 posteromedial to seta lm (Figure 8). Cupule ia posterior to seta c 3 , cupule im posterior to seta lm, cupule ip between setae h 1 and h 2 , cupule ih lateral to the anterior part of the anal opening. Opisthonotal gland opening lateral to seta lp, without dark sclerotized surrounding. Typical galumnid humeral organ absent, but porose area present anterolateral to seta c 3 (Figure 11a). Paraproctal valves (segment PS) glabrous. Chelicera and palp of larva smaller than in other instars, but of similar morphology, except for absence of tarsal eupathidium su (Figure 12a). Legs of larva stocky, all femora with ventral keel (Figure 9, 10a, b, 12b, 13). Most leg setae barbed, some setae (d on all femora, l on all genua and tibiae, pl’’ and most ft and pv on tarsi) thicker than other leg setae. Shape of prodorsum of protonymph, prodorsal setae, bothridium and bothridial seta as in larva, but seta in relatively longer, and bothridial seta slimmer than in larva. Gastronotum oval, with 15 pairs of setae because p-series added, and retained in subsequent nymphs (Figure 10b, 11b, 12c, d, 14a, b, 15, 16a–c). Setae of c-series as in larva, anterior part of gastronotum with ornamentation (Figure 11b, 15, 16a–c). In all nymphs, gastronotal shield with 10 pairs of setae (d-, l-, h-series, p 1 ), setae p 2 and p 3 inserted on unsclerotized integument; all relatively short and smooth. Four Figure 4. Galumna flagellata, adult, a – lateral aspect, legs partially drawn; scale bar 50 μm; b – anterior part of body, pteromorph removed, scale bar 50 μm; mouthparts, right side, scale bars 20 μm; c – chelicera (Trägårdh organ in “transparent” area); d – palp. INTERNATIONAL JOURNAL OF ACAROLOGY 5 pairs of porose areas present, Aa anteromedial to seta la, A1 posteromedial to seta lm, A2 posteromedial to seta lp and A3 between setae h 1 and h 2 . In protonymph, genital valves appearing on the large, porose genital shield, with one pair of genital setae inserted lateral to these valves, two pairs added in deutonymph and tritonymph each (Figure 10b, 14a, b), all short and smooth. In deutonymph, one pair of aggenital setae appearing on genital shields and three pairs of adanal setae on porose adanal shield, and remained in subsequent instars; all short and smooth. In protonymph and deutonymph, anal valves glabrous, in Figure 5. Galumna flagellata, leg segments of adult (part of femur to tarsus), right side, antiaxial aspect, scale bar 20 μm. a – Leg I, (pl’ on tarsus not illustrated); b – leg II, c – leg III; d – leg IV. 6A. SENICZAK ET AL. Figure 6. Galumna flagellata, adult, SEM micrographs. a – dorsal view; b – lateral view; c – frontal view; d – shape of pteromorph and setae, lateral view. Figure 7. Galumna flagellata, adult, SEM micrographs. a – porose area Aa; b – posterior part of notogaster, lateral view; c – open anal plate, lateral view; d – mouthparts, dorsal view. INTERNATIONAL JOURNAL OF ACAROLOGY 7 Figure 8. Galumna flagellata, larva, a – dorsal aspect, legs partially drawn, scale bar 20 μm; b – shape of seta le; c – shape of seta in (b, c enlarged). 8A. SENICZAK ET AL. (0–1)–1–2–1 (adult). The formula of genital setae is 1–3–5–6 (protonymph to adult), and formula of aggenital setae is 1–1– 1 (deutonymph to adult), and setal formula of segments PS–AN is 03333–0333–022. The ontogeny of leg setae and solenidia of G. flagellata is shown in Table 2. Distribution, ecology and biology Galumna flagellata has a central to southern Palearctic distribution (absent from eastern regions, Subías 2004), and is included in microand panphyto-phagous feeding groups (Hülsmann and Wolters 1998). The density of G. flagellata in terresial ecosystems is generally low (Paoletti 1988). This species prefers the litter or uppermost soil layer, and is considerably mobile and able to migrate upwards on plants (Smrž 1989). In this study, G. flagellata was most abundant during the first sampling (i.e., at the end of December 2018), one month after the litterbags were placed on the soil of Biodomo. This species achieved higher mean density in common lantana prunings (61 individuals per 500 cm 3 ) than in mango prunings (30 individuals per 500 cm 3 ). A relatively high abundance of G. flagellata (15 individuals per 500 cm 3 ) was noted in mango prunings in the second sampling (i.e. at the end of January 2019), while in other samplings this species was represented by single specimens or was absent. In the samples collected, the juveniles were more abundant (63% of all individuals) than the adults. The stage structure of this species for all samples was the following: 28 larvae, 39 protonymphs, 41 deutonymphs, 16 tritonymphs and 134 adults. In 50 randomly selected adults, the sex ratio (females to males) was 1:0.1, and 4% of females were gravid and carried one large egg (266 × 119), comprising 52% of the length of females. Comparison of morphological ontogeny of Galumna flagellata with congeners and remarks We compare the morphological ontogeny of G. flagellata with that of G. alata, G. curvifamulus, G. obvia and G. zachvatkini (Seniczak et al. 2012; Ermilov et al. 2017b; Grishina 1982, respectively, Table 3) to know the morphological differences between these species. Although the tritonymph of G. obvia is unknown, the other nymphs of this species are sufficient for this comparison. Morphology of G. flagellata is most similar to that of G. zachvatkini, and most characters concern the juveniles. The adult of G. flagellata differs from that of G. zachvatkini in sexual characters and location of lyrifissure im, whereas the juveniles differ in absence of typical galumnid humeral organ (versus present in G. zachvatkini), the shape of seta in in the tritonymph and shape of seta c 2 in the larva (Table 3). The morphology of G. flagellata differs most from that of G. curvifamulus and G. obvia. The adult of G. flagellata differs from those of G. curvifamulus and G. obvia in three morphological characters, and the juveniles differ in 10 morphological characters (Table 3). The adult of G. flagellata differs from that of G. alata in two morphological characters, and the juveniles differ in eight morphological characters. The nymphs of all species have a large, porose genital shield, whereas the presence of porose adanal shields depends on species (Table 3). Figure 16. Galumna flagellata, tritonymph, SEM micrographs. a – anterior part of gastronotum, dorsal view, b – anterior part of body, dorsal view, c – anterior part of body, lateral view, d – legs III and IV, lateral view. INTERNATIONAL JOURNAL OF ACAROLOGY 15 Figure 17. Galumna flagellata, leg segments of tritonymph (part of femur to tarsus), right side, antiaxial aspect, scale bar 10 μm, a – leg I, (pl’ on tarsus not illustrated); b – leg II; c – leg III; d – leg IV. 16 A. SENICZAK ET AL. The juveniles of all species of Galumnidae are generally similar to one another, have most prodorsal setae of medium size or long and barbed, their gastronotum is oval or roundish, and most gastronotal setae of nymphs are short (Sengbusch 1954; Woodring 1965; Seniczak 1971/72; Seniczak and Seniczak 2007; Seniczak et al. 2012; Ermilov et al. 2013, 2017a, b, Bayartogtokh and Ermilov 2017), and usually have typical galumnid humeral organ. From these morphological characters, the most important is the absence of typical galumnid humeral organ in the juveniles of G. flagellata, which broadens the diagnosis of juveniles of Galumna. However, there are porose areas present in the place of humeral organ, which requires more investigations, also in other species of Galumna with unknown juveniles. Among species of Galumna compared in Table 3, the ontogeny of leg setae is known in G. flagellata and G. curvifamulus. The former species differ from the latter species by the absence of seta v 1 on genua I and II of tritonymph (versus present in G. curvifamulus, Ermilov et al. 2017b), which is added in the adult. The juveniles of these species have most leg setae barbed, but femora of G. flagellata are thicker and have larger ventral keels than those of G. curvifamulus. The juveniles of most species of Galumnidae have the typical humeral organ, which is located in the sejugal plane, above the level of leg insertions at the dorsal margin of the epimeral plate (Seniczak and Seniczak 2007; Seniczak et al. 2012; Ermilov et al. 2013, 2017a, b, Bayartogtokh and Ermilov 2017). The juveniles of Table 2. Ontogeny of leg setae (Roman letters), solenidia and famulus (Greek letters) in Galumna flagellata. Leg Trochanter Femur Genu Tibia Tarsus Leg I Larva – d, bv’’ (l), σ (l), v’, φ 1 (ft), (tc), (p), (u), (a), s, (pv), (pl), ε, ω 1 Protonymph – – – – ω 2 Deutonymph – (l) – φ 2 – Tritonymph v’ – – v’’ (it) Adult – – v’ –v’, l’’ Leg II Larva – d, bv’’ (l), σ l’, v’, φ (ft), (tc), (p), (u), (a), s, (pv), ω 1 Protonymph – – – – – Deutonymph – (l) – l” ω 2 Tritonymph v’ – – v’’ (it) Adult – – v’ – – Leg III Larva – d, ev’ l’, σ v’, φ (ft), (tc), (p), (u), (a), s, (pv) Protonymph – – – – – Deutonymph v’ l’ –l’ – Tritonymph l’ – – v’’ (it) Adult – – – – – Leg IV Protonymph – – – – ft’’, (p), (u), (pv) Deutonymph – d, ev’ d v’, φ (tc), (a), s Tritonymph v’ –l’ l’, v’’ – Adult – – – – – Note: structures are indicated where they are first added and are present through the rest of ontogeny; pairs of setae in parentheses, dash indicates no additions. Table 3. Comparison of selected morphological characters of Galumna flagellata, G. alata, G. curvifamulus, G. obvia and G. zachvatkini; Gn – gastronotal. Characters G. flagellata G. alata 3 G. curvifamulus 2,3 G. obvia 4 G. zachvatkini 5 Formula of Gn setae 12–15–15–15–10 11–15–15–15–10 12 6 –15–15–15–10 11–15–15–15–10 12–15–15–15–10 Adult Shape of bs Fusiform Fusiform Clavate Fusiform Fusiform Length of seta in Long Long Short Short Long Location of im Not close to A1 Close to A1 Close to A1 Close to A1 Not close to A1 Median pore Present Absent Present Absent Present Sexual dimorphism Indistinct Indistinct Indistinct Indistinct Distinct Juveniles Shape of bs Clavate Clavate Clavate Fusiform Clavate Setae of c-series On microsclerites On microsclerites On microsclerites On microsclerites ? Humeral organ Absent Present Present Present Present Nymphs Length of seta le As long as le As long as le As long as le Shorter than le As long as le Length of seta in As long as le As long as le Longer than le Shorter than le Shorter than le Length of seta c 2 Longer than c 1 Longer than c 1 Longer than c 1 As short as c 1 Longer than c 1 Length of seta c 3 As long as c 2 Shorter than c 2 Longer than c 2 Longer than c 2 As long as c 2 Most Gn setae Short Short Alveolar Short Short Setae of p-series On ad-sclerite On ad-sclerite On microsclerites On microsclerites On ad-sclerite Setae of ad-series On integument On microsclerites On microsclerites On integument ? Larva Length of seta le As long as ro Shorter than ro As long as ro As long as ro As long as ro Length of seta in Shorter than le Longer than le As long as le Shorter than le Shorter than le Length of seta ex Medium sized Short Short Medium sized Medium sized Length of seta c 2 Longer than c 1 Longer than c 1 Longer than c 1 As short as c 1 As long as c 1 Length of seta c 3 As long as c 2 Shorter than c 2 As long as c 2 Longer than c 2 As long as c 2 Most Gn setae Medium sized Short Alveolar Short Medium sized 1 According to Seniczak et al. (2012), 2 adult according to Ermilov et al. (2017a), 3 juveniles according to Ermilov et al. (2017b), 4 according to Ermilov et al. (2013), 5 according to Grishina (1982), 6 including alveolar h 3 . INTERNATIONAL JOURNAL OF ACAROLOGY 17 G. flagellata lack the typical humeral organ, but have a large porose area in this place, which is unique in Galumnidae. According to Alberti et al. (1997), a humeral organ is a secretory porose organ, which is probably homologous to the humerosejugal porose organ Ah of adults, and has taxonomic importance (Norton and Alberti 1997). Except for the juveniles of Galumnidae, a humeral organ is also present in those of Oribatellidae, Ceratozetidae and Punctoribatidae (Norton and Behan-Pelletier 2009), but in these families, it is placed higher, near the posterolateral corner of the prodorsal shield. In the juveniles of Oribatellidae, a humeral organ is present in all species (Behan-Pelletier 2011; Behan-Pelletier and Walter 2012; Seniczak and Seniczak 2013; Seniczak et al. 2015, 2020a), except for Oribatella reticulata Berlese, 1916 (Seniczak et al. 2021). In the juveniles of Ceratozetidae, presence of humeral organ depends on subfamilies sensu Shaldybina (1972). In all species of Ceratozetinae, this organ is present (Behan-Pelletier and Eamer 2009; Seniczak et al. 2016b, 2017, 2018a), whereas in the juveniles of Sphaerozetinae this organ is generally present (summarized by Seniczak et al. 2016a), except for the larvae of Sphaerozetes olympicus Seniczak et al. (2016a) and Fuscozetes coulsoni A. and S. Seniczak, 2020 (Seniczak et al. 2016a; Seniczak and Seniczak 2020). In the juveniles of Trichoribatinae, a humeral organ is generally absent, but in some species, it is present (summarized by Seniczak et al. 2018c, 2019). In the juveniles of Punctoribatidae, a humeral organ is generally present (Behan-Pelletier et al. 2001; Behan-Pelletier and Eamer 2005, 2008; Seniczak and Seniczak 2008, 2018; Seniczak et al. 2018b, 2020b), except for Punctoribates sellnicki Willmann, 1928 (Seniczak and Seniczak 2008). Acknowledgments We are very grateful to two reviewers for helpful comments on an earlier version of the manuscript. We appreciate the financial support of this work by the Spanish Ministry of Economy and Competitiveness (Project CGL-2013-46665-R) and the European Regional Development Fund (ERDF). The authors also thank the Biodomo of the Science Park of the city of Granada for providing the space to carry out this experience. Disclosure statement No potential conflict of interest was reported by the author(s). ORCID Anna Seniczak http://orcid.org/0000-0003-0224-5397 Stanisław Seniczak http://orcid.org/0000-0001-7393-5606 References Alberti G, Klimek A, Seniczak S. 1997. Fine structure of the humeral organ of juvenile Edwardzetes edwardsii (Ceratozetidae, Oribatida) compared with porose areas of the adults. Acarologia. 38:275–287. Aoki J.1966. The large-winged mites of Japan (Acari: Cryptostigmata). Bulletin of the National Science Museum, Tokyo. 9(3):257–275. Bayartogtokh B, Ermilov SG. 2017. 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