Spatiodamaeus cf. fageti Bulanova-Zachvatkina, 1957

Bayartogtokh, Badamdorj, Burkitbaeva, Ulzhan D. & Enkhbayar, Tojoo, 2016, Lichenophilous species of Epidamaeus and Spatiodamaeus from high mountains of Mongolia, with remarks on their ontogeny (Acari: Oribatida), Zootaxa 4097 (3), pp. 451-474 : 463-470

Spatiodamaeus cf. fageti Bulanova-Zachvatkina, 1957

( Figs 8–11 )

Damaeus (Spatiodamaeus) fageti Bulanova-Zachvatkina, 1957 , p. 1179, figs. 8–11. Spatiodamaeus fageti: Bulanova-Zachvatkina 1967 , p. 143, pl. 6, fig. 92; 1975, p. 125, fig. 236; Miko 2006, p. 187, fig. 99c–h; Xie et al. 2012, p. 418.

Diagnosis. Adult of damaeid shape, large, dark brown to almost black in color, without exuvial scalp or adherent debris. Prodorsum with apophyses P; tubercles Da, Ba and Bp well developed. Sensillus short, nearly same width throughout its length, its distal 1/3 part finely barbed. Interlamellar seta long, nearly as long as sensillus. Notogastral setae 10 or 11 pairs (see Miko, 2006), thin, smooth, subequal in length; spina adnata of moderate size, conspicuously diverging distally as viewed in dorsal aspect, but strongly curved downwards from lateral view. Full complement of ventral enantiophyses E2, V and S strongly developed; epimeral region II with two pairs of setae; epimeral seta 1c inserted on large tubercle; discidium well developed, acute distally. Setae d on genua I–III much longer and thicker than respective coupled solenidia σ.

Deutonymph slimmer than adult, elongated, lightly pigmented. Prodorsal setae ro and le medium long, finely barbed, le conspicuously thicker than ro; setae in and ex relatively short; sensillus setiform, finely barbed. Gastronotum slightly elongate, with posterior excrescence; most of dorsal gastronotic setae very long, raised and inserted on large sclerites, setae of c -series and la finely barbed; setae of p -series relatively short. Cornicle thick, long, inserted at level of seta h 2.

Adult. Dimensions. Body length 647–720 Μm; length of notogaster 476–521 Μm; width of notogaster 415–451 Μm.

Integument. Adult dark brown to virtually black in color. Surface of body and legs with thick cerotegument having granular to short columnar excrescences. Only distal portions of leg tarsi, gnathosoma and setiform organs free of cerotegument. Cuticle microtuberculate conspicuously in lateral regions of prodorsum and around leg acetabula I and II. Exuvial scalps and adherent debris absent.

Prodorsum ( Fig. 8 A, C). Rostrum rounded in dorsal view, but conspicuously projecting anteroventrally in lateral view, with dark transverse band at level of setae ro in transmitted light due to contour of transverse groove and underlying rostrophragma. With pair of central swellings at level of legs I (above sigillae for cheliceral retractor muscles). Prodorsal enantiophyses A absent, but tubercles and Da, Ba and Bp well developed, nearly conical in shape, their tips rounded. Propodolateral apophysis P well developed, subtriangular. Prodorsal setae mostly smooth, only setae ro and in with minute barbs. Rostral seta 121 Μm in length, lamellar seta 139 Μm long, thin; interlamellar seta 117 Μm long, directed posterolaterad; exobothridial seta 65 Μm long. Sensillus 176 Μm long, nearly same width throughout its length, its distal 1/3 finely barbed. Bothridium typical of family, irregular funnelshaped, directed posterolaterad, with large opening ( Fig. 8 C).

Notogaster ( Fig. 8 ). Almost circular, slightly longer than wide. Spinae adnatae thin, moderate length (96 Μm), in dorsal view directed anterolaterally, but strongly incurved ventrad in lateral view; mutual distance slightly greater that of setal pair c 2. Ten pairs of notogastral setae medium in length, thin, smooth; seta h 1 absent; setae of c - and l -series 130–136 Μm, h -series 88–102 Μm, p -series 91–108 Μm in length. Seta c 1 directed anteriorly, c 2 laterally, other setae directed posterolaterally. Lyrifissures ia, im, ih, ip, ips and opisthosomal gland opening (gla) well developed.

Gnathosoma ( Fig. 8 B). Subcapitular mentum slightly wider than long. Mentum microtuberculate, subcapitular setae h 74 Μm, m 59 Μm, a 28 Μm long, thin, smooth. Chelicera 149 Μm in length, fixed and movable digits with three blunt teeth on each, setae cha and chb finely barbed. Palp slender, 112 Μm in length, palpal setation: 0–2–1– 3–9, including solenidion.

Epimeral region ( Fig. 8 B, C). Epimeral tubercles E2a, E2p, ventrosejugal tubercles Va and Vp well developed, large. Parastigmatic tubercles Sa and Sp subtriangular, Sa elongate, much longer than Sp. Discidium (di) elongate, spiniform, acute at tip. Epimeral setae thin, smooth; inserted on small tubercles; seta 1a 56 Μm, 1b 120 Μm, 1c 63 Μm, 2a 74 Μm, 2b 75 Μm, 3a 82 Μm, 3b 93 Μm, 3c 85 Μm, 4a 121 Μm, 4b 86 Μm, 4c 84 Μm and 4d 85 Μm in length. Epimeral setal formula: 3–2–3–4.

FIGURE 12. Adult (A–D) and deutonymph (E–H) of Spatiodamaeus cf. fageti , compound microscope images (not to scale). (A) Rostral seta of adult; (B) Sensillus of adult; (C) Interlamellar seta and spina adnata of adult; (D) Part of epimeral region showing parastigmatic tubercle in adult; (E) Gastronotic setae c 2 and la in deutonymph; (F) Cornicle k of deutonymph; (G) Gastronotic seta c 3 of deutonymph; (H) Posterior part of gastronotum showing insertions of setae h 1- h 3 and p 1 of deutonymph.

Ano - genital region ( Fig. 8 B, C). Anal and genital plates almost smooth, with sparse microtubercles. Genital opening 139 Μm in length and 125 Μm in width, anal opening 121 Μm long and 118 Μm wide. Ano-genital setae thin, smooth, genital setae 56–71 Μm, aggenital seta 81 Μm, anal setae 57–62 Μm, adanal setae 58–65 Μm in length. Adanal lyrifissure (iad) situated obliquely, at level of anal seta an 2.

Legs ( Figs 9 , 10 ). Structure of legs I–IV typical for genus, sub-moniliform. Trochanter and femur IV subequal in length; each with distal tectum rounded, not projecting. Setae d on genua I–III much longer and thicker than respective coupled solenidia σ; solenidia φ1 of tibia I and ω1 of tarsus I situated on distinct dorsal projections. Formula of leg setation (including famulus): I (1–7–4–4–21), II (1–6–4–4–17), III (2–4–4–4–16); IV (1–4–4–3– 15); formula of solenidia: I (1–2–2); II (1–1–2); III (1–1–0); IV (0–1–0). Homology of leg setae and solenidia as indicated in Table 2 .

Adult v ’ d, bv ”, (l), (v) d σ, (l), v ’ (l), (v), φ, d (ft), (tc), (p), (u), (a), s, (pv), ω1, ω2, (it), (v)

lost

Leg III

Deutonymph. Dimensions. Body length (excluding posterior excrescence of gastronotum) 488 µm, width of gastronotum 238 µm, length of gastronotum 323 µm.

Integument. Body cuticle yellowish to light brownish. Prodorsum, epimeral region and legs with tuberculate cerotegument. Tubercles of medium size, round to slightly elongate conical. Cuticle of medio-basal part of gastronotum with minute granules. Lateral body sides, epimeral and anogenital regions slightly folded. With securely attached exuvial scalp of previous instars.

Prodorsum ( Fig. 11 A). Subtriangular, relatively short, about 1/2 length of gastronotum. Rostrum widely rounded, rostral seta 67 µm long, setiform, finely barbed. Lamellar seta 80 µm in length, finely barbed, conspicuously thicker than ro, both setae without cerotegument. Interlamellar seta 32 µm long, truncate, smooth, blunt distally; exobothridial seta 30 µm long, pointed distally. Sensillus setiform, 144 µm long, with fine barbs. Bothridium irregular funnel shaped, with large opening.

Gastronotic region ( Fig. 11 A, B). Slightly elongate, with large posterior excrescence bearing setae h 1 and p 1. Gastronotic setae inserted on isolated sclerotized tubercles, except tubercle of pair h 1 connected by inconspicuous medial sclerite. With 12 pairs of gastronotic setae (с 1– с 3, la, lm, lp, h 1– h 3, p 1– p 3); most of dorsal setae very long; setae of c -series and la finely barbed, other setae smooth; setae c 3 and p -series relatively short. Seta c 1 262 µm, c 2 256 µm, c 3 70 µm, la 253 µm, lm 202 µm, lp 189 µm, h 1 304 µm, h 2 125 µm, h 3 154 µm, p 1 64 µm, p 2 61 µm, p 3 54 µm in length. Cupules ia, ih, ips and opisthosomal gland opening (gla) clearly developed. Cornicle (k) by which gastronotic exuviae of previous instars firmly attached, thick, elongate and tapered terminally, 115 µm long, inserted at level of seta h 2. Protonymphal exuvial scalp of reticulate granular sculpture, without additional adherent materials, firmly fastened to gastronotum, and located directly over the central region ( Fig. 11 C); with nine pairs of setae (с 1, с 2, с 3, la, lm, lp, h 1, h 2, h 3).

Gnathosoma ( Fig. 11 B). Subcapitular setae a, m and h of medium size, 9–14 µm, setiform, smooth. Adoral setae short, thin, smooth. Palp with setation 0–2–1–3–9(+ω). Solenidion (ω) of palptarsus thickened, straight, blunt-ended. Chelicera with two setiform setae, cha longer than chb. Trägårdh’s organ (Tg) inconspicuous.

Epimeral region ( Fig. 11 B). Epimeral setae simple, thin, smooth, without cerotegument; setae 1b and 3b about twice as long as other setae. Setal formula of epimeres: 3–1–2–2.

Ano-genital region ( Fig. 11 B). Genital papillae sub-equal in size; adanal cupules iad well developed. Genital, aggenital and anal setae thin, smooth; three pairs of genital (right plate with four setae), one pair of aggenital and three pairs of adanal setae. Cupules ih and ips appearing in normal ontogenetic pattern.

Legs. Tarsus I and tibia I relatively thin, solenidion φ1 on tibia I very long, slightly flagellate, with coupled seta d. Solenidia on tibiae II–IV of medium size or short, thickened, straight, with respective coupled setae d; famulus ε regressive, sunken, submerged in fovea with sclerotized, cup-like elevated rim. Most setae of legs barbed, except p on tarsi. Formulas of leg setation: I (1–4–4–5–16), II (1–4–4–4–13), III (2–3–3–4–13), IV (0– 2 –3–3–12), formula of solenidia: I (1–2–2), II (1–1–2), III (1–1–0); IV (0–1–0). Homology of leg setae and solenidia as indicated in Table 2 .

Material examined. Two adults (male and female) and one deutonymph: Khuitnii-Am area, Mts Mongol Altai, close to Lake Dayan, District Sagsai, Province Bayan-Ulgii, fruticose lichens growing on larch tree barks ( Larix sibiricus Ledebour, 1833 ), N48o14’, E88o55’, elevation 2356 m a.s.l., 18 July 2010, Col. B. Bayartogtokh.

Remarks. As mentioned above, due to inadequate original definition, the identity of some of the known species of Spatiodamaeus had long been in doubt. One of such inadequately defined species is S. fageti (see Bulanova-Zachvatkina, 1967, 1975; Cancela da Fonseca and Bahou, 1970; Miko, 2006). When first trying to determine the specific name of our materials, we were doubted due to lack of the detailed definition of these disputable species, and therefore, the present identification can be questioned. However, our identification is based on the diagnoses of selected species of Spatiodamaeus by Miko (2006) and Xie et al. (2012), and oriented on such characters of adults as anterior notogastral setae not strongly curved, and these setae are neither darkly colored nor thicker than other setae, but more or less straight, similar to other setae in size and color; interlamellar setae long, nearly as long as sensilli; formula of setation on genua of legs: 4–4–4–4; formula of trochanter: 1–1–2–1. Further studies on topotypic material are important for making sure if our identification is correct.

It is worth to mention that Miko (2006) noted 11 pairs of notogastral setae in adults of S. fageti , but we observed only 10 pairs in our studied materials. Similarly to our observation, Seniczak et al. (2013) showed 10 pairs of notogastral setae in adults of S. verticillipes (Nicolet, 1855) , and noted lacking one of the setae of h -series. For S. verticillipes , it is apparently an ontogenetic loss as tritonymph of this species has complete set of setae h -series.

Deutonymph of this species can be differentiated from those of other species of Spatiodamaeus , the immature morphology of which is known, by the 1) relatively short sensillus and gastronotic setae c 1, c 2, lm, lp as opposed to very long sensilli and respective gastronotic setae in juveniles of other species; 2) relatively thick nymphal cornicle in contrast to the narrow cornicles in juveniles of other species.

Distribution and habitat ecology. This species, which until now had been reported only from central and eastern Europe ( Germany, Poland, Czech Republic, Slovakia, Ukraine and European Russia), has been collected from the high mountainous area in western Mongolia. This is the first record of this species in Asia. As for habitat ecology, Bulanova-Zachvatkina (1957a) noted that S. fageti preferred litter of oak forest, mosses growing on trunks of oak and beech trees and decaying wood. According to Miko (2006), this species inhabits the litter and wet moss cushions in deciduous and mixed forests as well as peatlands. We found both adults and a deutonymph of this species from the fruticose lichens ( Usnea sp.) growing on larch tree trunk in a high mountainous area.

Figures

FIGURE 8. Adult of Spatiodamaeus cf. fageti. (A) Dorsal view, legs partly shown; (B) Ventral view, legs partly shown; (C) Lateral view, without legs.

FIGURE 9. Adult of Spatiodamaeus cf. fageti. (A) Tibia and tarsus of leg I, right, antiaxial view; (B) Femur and genu of leg I, right, antiaxial view; (C) Genu and tibia of leg II, right, antiaxial view (slightly twisted).

FIGURE 10. Adult of Spatiodamaeus cf. fageti. (A) Genu and tibia of leg III, right, antiaxial view; (B) Tibia and tarsus of leg IV, right, antiaxial view (slightly twisted); (C) Trochanter, femur and genu of leg IV, right, antiaxial view (slightly twisted).

FIGURE 11. Deutonymph and protonymphal exuvial scalp of Spatiodamaeus cf. fageti. (A) Dorsal view, legs partly shown; (B) Ventral view, legs partly shown; (C) Protonymphal exuvial scalp.

Tables

TABLE 2. Leg setation and solenidia in adult and deutonymph of Spatiodamaeus fageti (setae in parentheses represent pairs).

Instars	Trochanter	Femur	Genu	Tibia Tarsus
Leg I
Deutonymph	v ’	d, (l), bv ”	d σ, (l), v ’	(l), (v), d φ1, φ2 (ft), (tc), (p), (u), (a), s, (pv), (pl), ε, ω1, ω2
Adult	v ’	d, (l), bv ”, (v 1), v 2”	d σ, (l), v ’	(l), (v), φ1, φ2, (ft), (tc), (p), (u), (a), s, (pv), (pl), ε, ω1, ω2, d lost (it), (v 1), v 2
Leg II
Deutonymph	v ’	d, bv ”, (l)	d σ, (l), v ’	d φ, (l), v ’ (ft), (tc), (p), (u), (a), s, (pv), ω1, ω2