Galumna flagellata Willmann, 1925

Galumna flagellata Willmann, 1925 View in CoL

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 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 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 View Figure 1 View Figure 2 View Figure 3 View Figure 4 ). Hypostomal setae short, h and m slightly longer than a ( Figure 2 View Figure 2 ). Cheliceral setae cha longer and thicker than chb, both barbed ( Figure 4c View Figure 4 ), most palp setae finely barbed ( Figure 4d View Figure 4 , 7d View Figure 7 ), 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 View Figure 5 , 6b View Figure 6 , 7a View Figure 7 ). Solenidia ω 1 and ω 2 on tarsus I of similar length, seta ft” short ( Figure 5a View Figure 5 , 6b–d View Figure 6 ). 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.

Description of juveniles

Larva egg-shaped in dorsal view ( Figure 8 View Figure 8 , 9a View Figure 9 ), light brown. Prodorsum subtriangular, prodorsal setae of medium size (in, ex) or long (ro, le, Table 1 View 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 View Figure 8 , 10a View Figure 10 , 11a View Figure 11 ) 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 View 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 View 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 View Figure 11 ). 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 View Figure 12 ). Legs of larva stocky, all femora with ventral keel ( Figure 9 View Figure 9 , 10a, b View Figure 10 , 12b View Figure 12 , 13 View Figure 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 View Figure 10 , 11b View Figure 11 , 12c, d View Figure 12 , 14a, b View Figure 14 , 15 View Figure 15 , 16a–c View Figure 16 ). Setae of c -series as in larva, anterior part of gastronotum with ornamentation ( Figure 11b View Figure 11 , 15 View Figure 15 , 16a–c View Figure 16 ). 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 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 View Figure 10 , 14a, b View Figure 14 ), 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 tritonymph two pairs of short and smooth anal setae present. In tritonymph, cupules ia, im and ip as in larva, cupule iad lateral to the anterior part of anal valves, cupules ips and ih displaced lateral and anterolateral to iad, respectively ( Figure 11b View Figure 11 , 14b View Figure 14 ). Typical galumnid humeral organ absent, but porose area present anterolateral to seta c 3. Opisthonotal gland opening lateral to seta h 3, without dark sclerotized surrounding ( Figure 11b View Figure 11 ). Legs of tritonymph stocky, all femora with ventral keel ( Figure 12b View Figure 12 , 16 View Figure 16 , 17 View Figure 17 ). Most leg setae barbed, some setae (d on all femora, l on all genua and tibiae, pl’’ and most pv on tarsi and ft on tarsi I–III) thicker than other setae.

Summary of ontogenetic transformations

In all juveniles, the prodorsal setae ro and le are longer than in, whereas in the adult seta in is longer than ro and le. Seta ex is of medium size in the juveniles, and short in the adult. The bothridium is rounded in all instars, but in the adult, it is covered by anterior tectum of notogaster. In all juveniles, the bothridial seta is clavate, with barbed head, which in the larva is thicker than in the nymphs, whereas in the adult the bothridial seta is fusiform, with narrow, barbed head. The larva has 12 pairs of gastronotal setae, including h 3, the nymphs have 15 pairs (p -series appearing in protonymph), whereas the notogaster of adult loses all setae and alveoli of setae c 1, c 3 and of d -series, such that 10 pairs of alveolar setae remain. The formula of gastronotal setae in G. flagellata is 12–15–15–15-10 (from larva to adult), the formulas of epimeral setae are 3–1–2 (larva, including scaliform 1 c), 3–1–2–1 (protonymph), 3–1–2–2 (deutonymph), 3–1–3–3 (tritonymph) and 1– (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 View 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 micro- and 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 View 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 View 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 View 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 View Table 3 ). 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 View 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 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. 2016 b, 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).