Licnobelba latiflabellata ( Paoli, 1908 )

Seniczak, Stanisław, Ayyıldız, Nusret & Seniczak, Anna, 2012, Setal losses in the dorsal hysterosoma of Plateremaeoidea (Acari: Oribatida) in the light of ontogenetic studies, Journal of Natural History 46 (7 - 8), pp. 411-451 : 437-446

Licnobelba latiflabellata ( Paoli, 1908)

( Figures 9D,E , 11B , 12B , 20–26 )

Licneremaeus latiflabellatus Paoli, 1908 .

Licnobelba alestensis Grandjean, 1931 .

Licnobelba montana Mihelčič, 1957 .

Licnobelba latiflabellata: Grandjean 1934a ; Bernini et al. 1987; Pérez-Íñigo 1993; Schatz and Schatz 2009; Mahunka and Mahunka-Papp 2010.

Diagnosis

Adult brown, rather small (266–329 µm), with rather short setae ro and le, short seta in, and minute seta ex ( Figure 20 , Table 1). Bothridium large, rounded, sensillus long, with spatulate, barbed head. Body and setae covered with granules of cerotegument.

Notogaster oval, with transverse ridge on anterior part of notogaster ( Figure 21C ), four pairs of posterior setae (h 1, p 1 – p 3), and large gland opening gla, protruding above surface of notogaster. Adult with exuvial scalps of juveniles ( Figure 21A,B ), loosely connected to notogaster. Genital plates relatively large ( Figure 12B ), some parts of anogenital region with thick layer of cerotegument ( Figure 22B–D ). Formula of leg setae (and solenidia): I – 1-5-4(1)-4(2)-19(2); II – 1-5-4(1)-5(1)-16(2); III – 2-3-3(1)-4(1)-13; IV – 1-3-3-4(1)-13. Legs tridactylous.

Juveniles with plicate cuticle, unpigmented. Prodorsal setae ro and le rather long, curved, other setae short. Gastronotal setae also short, except long and raised h 1 in nymphs, inserted in posterior part of gastronotum. Tritonymph with long, thick anteromedial projection, covering setae c 1, and extending beyond anterior margin of gastronotum; projection and most setae covered with granular cerotegument. Larva with 11 pairs of setae (h 3 absent), nymphs with seven pairs (d -series, l -series and h 2 lost, p -series appear). Nymphs with exuviae of previous instars, loosely connected to gastronotum, and well-formed posterior excrescence bearing long, raised seta h 1.

Description of juvenile stages

Larva unpigmented, with plicate cuticle, subtriangular prodorsum, and lateral depression at level of leg I ( Figure 23 ). Prodorsal setae rather short, length decreasing from ro to in, seta ex longer than in ( Table 1). Bothridium rounded, sensillus with spatulate head.

Gastronotum with 11 pairs of small setae, seta h 3 absent ( Figure 24A ). Paraproctal valves (segment PS) with two pairs of small setae. Gland opening gla and cupules as in larva of Licnodamaeus costula . Body and most setae covered with granules of cerotegument.

Nymphs slimmer than larva, unpigmented, and with plicate cuticle. Gastronotum of protonymph with seven pairs of setae (d -series, l -series and h 2 lost, p -series added), which remain in deutonymph and tritonymph; all setae short, except for long and raised h 1, inserted on posterior excrescence. Genital valves of protonymph with pair of short setae ( Figure 24B ), two pairs added in deutonymph ( Figure 25A ) and two more pairs added in tritonymph ( Figure 25B ). One pair of aggenital setae appears in deutonymph, lateral to posterior region of genital valves, and remains in tritonymph. Paraproctal valves of protonymph (segment AD) and deutonymph (segment AN) glabrous, those of tritonymph with two pairs of small setae. In deutonymph three pairs of adanal setae (ad 1 – ad 3) appear on segment AD, and remain in tritonymph; these setae smaller and thinner than p -series. Body and most setae covered with granules of cerotegument.

Prodorsum of tritonymph ( Figure 26 ) relatively shorter than in larva, but prodorsal setae as in larva. Gastronotal setae small and in marginal position on gastronotum, as in Licnodamaeus costula . Gastronotum with long, thick anteromedial projection, extending beyond anterior margin of gastronotum, and covering setae c 1. Seta h 1 long, raised and curved anteriorly; other setae small, but posterior setae thicker than anterior setae. Gland opening gla anterolateral to seta p 3. Cupules ia and im as in larva, cupule ip anterolateral to seta p 2, cupule iad lateral to anterior part of anal opening, cupules ips and ih not observed in folded cuticle, covered with cerotegument. Nymphs usually with exuvial scalps of previous stages ( Figure 18B ), loosely connected to gastronotum, and well-formed posterior excrescence, with long and anteriorly curved seta h 1. Tarsus I rather short, with two curved solenidia, ω 1 longer than ω 2, tarsus and some setae covered with granular cerotegument, famulus ε not observed ( Figure 9D,E ). Tibia with two solenidia, ϕ 1 long, ϕ 2 short, and setae l covered with granular cerotegument.

Ontogenetic transformations

During ontogeny of Licnobelba latiflabellata five pairs of setae are present on the prodorsum, including a sensillus. In all instars prodorsal and gastronotal setae are short, except for setae ro and le, which are longer. The sensillus has a spatulate head. The larva has 11 pairs of gastronotal setae, the nymph have seven pairs (d -series, l -series and h 2 lost, p -series appears), whereas the adult loses setae of the c -series ( Table 2), so that four pairs of notogastral setae remain (h 1 and p -series). The nymphs develop a characteristic medial projection above setae c 1; it is not observed in the protonymph, is small, but distinct in the deutonymph, and is large and thick in the tritonymph, extending beyond the anterior margin of the gastronotum. The nymphs also develop a distinct posterior excrescence, bearing raised and curved anteriorly seta h 1. The adult carries the exuvial scalps of juveniles ( Figure 11B ), which are fastened to the notogaster by strong, springy anterior projection, and are protected against loss by raised, and curved anteriorly seta h 1 (if we try to raise the exuviae above the notogaster, the process projection presses them to the notogaster again). The formula of gastronotal setae is 11-7-7-7-4 (larva to adult), the formula of segments PS–AN is 23333-0333-022, and the formulae of coxisternal and genital setae are as in Licnodamaeus costula ( Table 3).

Distribution and ecology

According to Subíasc (2004, 2011) Licnobelba latiflabellata is a Palaearctic occidental species, except absent from northern regions, while Schatz and Schatz (2009) consider it Palaearctic. This species inhabits the soil under dry litter, especially of pine, juniper and box trees, but also mosses on soil ( Pérez-Íñigo 1993). It is frequent in mountains, but also occurs in the lowland landscapes. Grandjean (1934a) found it to be very common in the forest litter near Taza and Azrou (Ifrane, Ain Leuh, Middle Atlas, Morocco), near the spring of the river Oum er Rebia, between 1100–1850 m above sea level), and in Tadlest (Grand Atlas, 2100 m above sea level). Bernini et al. (1987) recorded this species in the Pollino Massifs (Southern Italy), Mahunka and Mahunka-Papp (2010) in oak forest in Karitsa (Larisa county, Greece), while Migliorini (2009) found it in Holm oak ( Quercus ilex L.) vegetation near Planotzara (Carbonia-Iglesias province, Sardinia, Italy). Schatz and Schatz (2009) recorded this species from leaf litter under Holm oak shrubs in Isola del Garda island in Lake Garda (northern Italy, southern slope of the Alps). In Catalunya ( Spain) this species lives in litter under cypress trees in mountains (Montserrat Monastery, 41 ◦ 35.31 ′ N, 01 ◦ 50.07 ′ E, 763 m above sea level).

Setal losses on the dorsal hysterosoma during ontogeny of Plateremaeoidea

Aleurodamaeus setosus , Licnodamaeus costula and Licnobelba latiflabellata represent interesting species of Plateremaeoidea, which have in the adults relatively few setae, all positioned on the posterior part of the notogaster. However, the intensity of loss of these setae does not depend on the number of gastronotal setae in nymphs. For example, adults of Al. setosus and Licnobelba latiflabellata have four pairs of notogastral setae, but the nymphs of the former species have 12 pairs of gastronotal setae, whereas those of the latter species have only seven pairs. For a broader view, we can also compare respective instars of other well-studied members of Plateremaeoidea. These include Ar. reticulatus , G. bicostatus and J. neonominata – as described by Seniczak and Seniczak (2011a) – and Aleurodamaeus africanus and Pedrocortesella africana – investigated by Ermilov et al. (2010).

Considering the larva, some species like Al. setosus , Al. africanus and Licnodamaeus costula have the full complement of gastronotal setae that is associated with Grandjean’s unideficiency nomenclature ( Grandjean 1953). However, other species ( Ar. reticulatus , G. bicostatus , J. nominata and Licnobelba latiflabellata ) lack seta h 3, and P. africana lacks also setae la and lm ( Table 2).

The protonymphs of all these species lose setae of the d -series. In some species ( Al. setosus and Al. africanus ) no other setae are lost, so that 12 pairs (c -, l -, h - and p -series) remain in the nymphs. Interestingly, in both species seta lm translocates in the direction of seta lp, which results in a large glabrous area of the gastronotum that is commonly associated with bearing exuvial scalps by nymphs. The adults of these species lose eight further pairs of notogastral setae (l -series, c -series, h 3 and h 2), so that only four pairs remain (h 1 and p -series).

The protonymphs of Ar. reticulatus , G. bicostatus and J. neonominata lose setae of d -series and setae la and lm, so that these and subsequent nymphs retain 10 pairs of gastronotal setae (lp and c -, h - and p -series). The adult of Ar. reticulatus further loses seta lp and the c -series, so that six pairs of notogastral setae (h -series and p -series) remain ( Seniczak and Seniczak 2011a). Balogh and Balogh (1992) and Pérez-Íñigo (1997) noted species of Arthrodamaeus with five pairs of notogastral setae; these probably also lose seta h 3. The adult of G. bicostatus loses five pairs of notogastral setae (lp, c -series and h 3), whereas that of J. neonominata loses six pairs (lp, c -series and h 3 and h 2), so that five pairs remain in the former species (h 2, h 1 and p -series), and four pairs in the latter species (h 1 and p -series), as in Al. setosus .

The protonymphs of Licnodamaeus costula and Licnobelba latiflabellata lose all setae of the d -series and l -series, and the latter species also loses seta h 2, so only nine pairs of setae remain in nymphs of the former (c -, h - and p -series), and seven pairs in the latter species (h 1 and c - and p -series). The adults of these species lose setae of the c -series, so that six pairs remain in Licnodamaeus costula (h -series and p -series), and four pairs in Licnobelba latiflabellata (h 1 and p -series), as in Ar. reticulatus and J. neonominata .

The setal ontogeny of P. africana differs distinctly from that of other studied Plateremaeoidea. According to Ermilov et al. (2010), its larva has nine pairs of gastronotal setae (lacks la, lm and h 3), and nine pairs are present in the nymphs (lost d -series, adds p -series). The adult, on which they did not report, has five pairs of notogastral setae ( Pletzen 1963), probably h 2, h 1 and the p -series.

The juveniles of species discussed here differ also in the pattern of cuticle. Aleurodamaeus setosus , Al. africanus and Ar. reticulatus have it smooth, while the other species have it plicate ( Table 3). Most species have setae on the paraproctal valves of the larva; the exception is P. africana , which has paraproctal valves glabrous. The genital setation also varies in species, both in adult number and in ontogenetic pattern: Al. setosus , Ar. reticulatus and G. bicostatus share the formula 1-4-6-7, whereas additions are slower in J. neonominata (formula 1-3-4-7) and Licnodamaeus costula and Licnobelba latiflabellata (formula 1-3-5-6) lack the seventh seta. Other morphological characters are listed in Table 3.

Figures

Figure 9. Tarsus I and part of tibia I of tritonymph, scale bars 20 µm. (A) Aleurodamaeus setosus, paraxial aspect; (B) Licnodamaeus costula, fragment of tarsus with solenidia; (C) L. costula, paraxial aspect; (D) Licnobelba latiflabellata, fragment of tarsus with solenidia; (E) L. latiflabellata, paraxial aspect. Explanation of labels in text.

Figure 11. Lateral aspect of adults, scale bars 100 µm. (A) Licnodamaeus costula; (B) Licnobelba latiflabellata. Legs partially drawn. Explanation of labels in text.

Figure 12. Adult, anogenital region, scale bars 50 µm. (A) Licnodamaeus costula; (B) Licnobelba latiflabellata. Explanation of labels in text.

Figure 18. Lateral aspect of tritonymphs, scale bars 100 µm. (A) Licnodamaeus costula; (B) Licnobelba latiflabellata. Legs partially drawn. Explanation of labels in text.

Figure 20. Licnobelba latiflabellata, adult, dorsal aspect, scale bar 50 µm. Legs partially drawn. Explanation of labels in text.

Figure 21. Licnobelba latiflabellata, adult, scanning electron micrographs. (A) Lateral aspect; (B) hysterosoma, lateral aspect; (C) dorsal aspect, scalps removed; (D) anterior region, ventral aspect.

Figure 22. Licnobelba latiflabellata, adult, scanning electron micrographs. (A) Prodorsum and anterior part of notogaster; (B) ventral aspect; (C) anogenital region; (D) anogenital region.

Figure 23. Licnobelba latiflabellata, larva, dorsal aspect, scale bar 50 µm. Legs partially drawn. Explanation of labels in text.

Figure 24. Licnobelba latiflabellata, scale bars 50 µm. (A) Anal region of larva; (B) anogenital region of protonymph. Explanation of labels in text.

Figure 25. Licnobelba latiflabellata, anogenital region, scale bar 50 µm. (A) Deutonymph; (B) tritonymph. Explanation of labels in text.

Figure 26. Licnobelba latiflabellata, tritonymph, dorsal aspect, scale bar 100 µm. Legs partially drawn. Explanation of labels in text.