Epidamaeus munkhbayari Bayartogtokh

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 : 453-462

Epidamaeus munkhbayari Bayartogtokh , sp. nov.

( Figs 1–7 )

Diagnosis. Prodorsum with a pair of central swellings at level of legs I, surrounded laterally by distinct semicircular ridges; another pair of semicircular ridges developed between alveoli of interlamellar setae, with pair of small tubercles at its posterior end. Prodorsal tubercle Ba well developed, enantiophyses A and D absent. Sensillus medium long, thin, with minute sparse barbs, sometimes covered with conglomerate of cerotegument in distal half, finely attenuate. Prodorsal setae mostly smooth except sensillus. Notogaster without exuvial scalp or adherent debris. Notogastral setae aligned in two subparallel rows, except c 1 directed posteriad, medium long, thin, mostly smooth, with basal vane; spina adnata of moderate size. Tectum of podocephalic fossa conspicuously developed, laterally produced as relatively short, subtriangular tooth underneath trochanter I; ventral tubercles E2a, Va and Vp well developed; epimeral setae 1b, 1c and 3a inserted on large tubercles. Setae d on genua I–III nearly as long as their associated solenidia σ.

Juveniles unpigmented, most part of body and legs covered with granular cerotegument. In larva, pair of rostral as well as lamellar setae inserted close to one another, nearly in square, but in nymphs these setae spaced widely, inserted in transversally elongated rectangle. Sensilli setiform, smooth in larva and deutonymph, but scarcely barbed in tritonymph. Most dorsal gastronotic setae very long, except for shorter setae c 3, la, lm in larva, and seta c 3 in nymphs. Seta h 3 present in larva; cornicle thick, elongate and tapered terminally, located at level of seta h 3; nymphs carry exuviae of previous instars.

Adult. Dimensions. Body length 427–494 (464) Μm; length of notogaster 278–366 (323) Μm; width of notogaster 262–317 (298) Μm. Totally 16 specimens were measured.

Integument. Adult yellowish brown. Surface of body and legs with thick cerotegument having granular to short columnar excrescences. Cuticle microtuberculate conspicuously on lateral regions of prodorsum and around leg acetabula I and II. Exuvial scalps and adherent debris absent.

Prodorsum ( Figs 1 , 4 ). Rostrum rounded in dorsal view, but slightly projecting anteroventrally in lateral view. With pair of central swellings at level of legs I (above sigillae for cheliceral retractor muscles), surrounded laterally by distinct semicircular ridges ( Figs 1 A, D, 4A, H). Another pair of semicircular ridges developed between alveoli of interlamellar setae, with pair of small tubercles at posterior end ( Figs 1 A, D, 4G, H). Development degree of these two pairs of ridges different in various specimens. Prodorsal enantiophyses A and D absent. Postbothridial tubercle Ba well developed, nearly triangular in shape, its tip usually rounded, but sometimes acute ( Figs 1 A, D, 4E). Propodolateral apophysis absent. Prodorsal setae mostly smooth, only sensillus with sparse weak barbs. Rostral seta (ro) 58–80 Μm in length, thin; lamellar seta (le) 64–90 Μm long, thin; interlamellar seta (in) 42–64 Μm long, slightly thinner than ro and le, directed posteromediad; exobothridial seta (ex) 35–42 Μm long. Sensillus (ss) 144–150 Μm long, thin, with minute sparse barbs, finely attenuate, but not flagellate; sometimes covered with conglomerate of cerotegument in distal half ( Figs 1 B, 4F). Bothridium typical of family, irregularly funnel-shaped, directed posterolaterad, with large opening ( Figs. 1 B, 4G).

Notogaster ( Figs 1 , 4 ). Almost circular, slightly longer than wide, without exuvial scalp or adherent debris. Spinae adnatae (sa) thin, moderate length (80–96 Μm), in dorsal view directed anteromedially, but slightly incurved dorsally in lateral view; mutual distance slightly greater than that of setal pair c2 (Figs, 1A, D, 4D, H). Notogastral setae appear thin, with minute barbs; setae of c - and l -series 67–74 Μm, h -series 61–67 Μm, p -series 29–38 Μm in length. As viewed in dorsal aspect, seta c 1 directed anteriorly, c 2, l - and h rows directed posteriorly, whereas setae of p rows directed laterally. Lyrifissures ia, im, ih, ip, ips and opisthosomal gland opening (gla) well developed ( Fig. 1 A, C).

Gnathosoma ( Figs. 1 C, 3D, E). Subcapitular mentum slightly wider than long. Mentum microtuberculate, subcapitular setae h 38–51 Μm, m 35–48 Μm, a 22–29 Μm long, thin, with minute barbs. Chelicera 109 Μm in length, fixed and movable digits with three blunt teeth on each; setae cha and chb finely barbed ( Fig. 3 D). Palp slender, 106 Μm in length, palpal setation: 0–2–1–3–9, including solenidion ( Fig. 3 E).

Epimeral region ( Figs 1 C, 4B, C). Tectum of podocephalic fossa conspicuously developed, laterally produced as relatively short, subtriangular tooth (t) directed underneath trochanter I ( Fig. 1 C). Epimeral tubercle E2a, ventrosejugal tubercles Va and Vp well developed, large, subtriangular, nearly rounded at tip ( Figs 1 C, 4B). Parastigmatic tubercles Sa subtriangular, elongate, slightly longer than nearly pentagonal, blunter Sp. Discidium (di) nearly triangular, acute at tip. Epimeral setae thin, with minute barbs; setae 1b, 1c and 3a inserted on large tubercles, whereas other setae situated on small tubercles ( Fig. 1 C); seta 1a 26 Μm, 1b 61 Μm, 1c 38 Μm, 2a 29 Μm, 3a 35 Μm, 3b 32 Μm, 3c 32 Μm, 4a 38 Μm, 4b 42 Μm, 4c 48 Μm and 4d 42 Μm in length. Epimeral setal formula: 3– 1–3–4.

Ano - genital region ( Fig. 1 C, D). Anal and genital plates almost smooth, with sparse microtubercles. Anogenital setae thin, smooth, genital setae 29–32 Μm, aggenital seta 38 Μm, anal setae 38–45 Μm, adanal setae 32–35 Μm in length. Adanal lyrifissure (iad) situated obliquely, at level slightly anterior to anal seta an2.

Legs ( Figs 2 , 3 A, B, C). 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 nearly as long as their associated solenidia σ; solenidia φ1 of tibia I and ω1 of tarsus I situated on distinct dorsal projections. Formula of leg setation (including famulus): I (1–7–4–4–20), II (1–6–4–4–17), III (2–4–3–3–17); IV (1–4–3–3–14); 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 1 .

*Though the protonymph is unknown, its probable setal complement is hypothesized in this table; Norton (1977b) found no variation in protonymphal setation of Damaeidae .

Larva, deutonymph and tritonymph. Dimensions. Body length of larvae 282–333 (313) µm, width of gastronotum 157–192 (171) µm; body length of deutonymph 360 µm, width of gastronotum 192 µm; body length of tritonymph: 403 µm, width of gastronotum 221 µm. Three larvae, one deutonymph and one tritonymph were measured.

Integument. Body cuticle pale to light brownish. Prodorsum, epimeral region and legs with tuberculate cerotegument. Tubercles of medium size, round to conical. Cuticle of medio-basal part of gastronotum with minute granules. Nymphs with firmly attached exuvial scalps of previous instars, but no adherent debris.

Prodorsum ( Figs 5 A, 6A, 7A). Subtriangular, relatively short, about 1/2–1/3 length of gastronotum. Rostrum rounded, rostral setae setiform, smooth, conspicuously shorter and thinner than lamellar setae, both setae without cerotegument; mutual distance between pairs of setae ro–ro and le–le in larva much shorter than those in nymphs. Interlamellar seta longer, but thinner, distally pointed in larva than relatively short, truncate, blunt ended seta in nymphs; exobothridial seta medium long, pointed distally, similar in size in all studied stages. Sensillus setiform, medium long, smooth in larva and deutonymph, but with fine barbs in tritonymph. Bothridium irregular funnel shaped, with large opening in all studied juvenile instars.

Gastronotic region ( Figs 5 , 6 , 7 ). Slightly elongate, with large posterior excrescences bearing setae dp in larva and h 1 in nymphs. Gastronotic setae inserted on isolated sclerotized tubercles, except for tubercles of pairs c 1 and dp, each respectively connected by inconspicuous medial sclerite in larva. Larva with 12 pairs of gastronotic setae (с 1– с 3, da, dm, dp, la, lm, lp, h 1– h 3); most of dorsal setae very long, but setae с 3, la, lm, h 2 and h 3 relatively short. Cupules ia, ih, ip and opisthosomal gland opening (gla) well developed. Deutonymph and tritonymph 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, raised and inserted on large sclerites; setae с 3, p 1– p 3 relatively short; p 2 and p 3 much thinner than other setae, slightly flagellate distally. Cupules ia, ih, ips and opisthosomal gland openings (gla) clearly developed. Cornicle (k) by which gastronotic exuviae of previous instars firmly attached, thick, elongate and tapered terminally, inserted at level of seta h 2. Protonymphal exuvial scalp of reticulate granular sculpture ( Fig. 6 C), without additional adherent materials, firmly fastened to gastronotum, and located directly over the central region; with eight pairs of setae (с 1, с 2, la, lm, lp, h 1– h 3). Setation of gastronotum in tritonymph same as in previous nymphal instar, but setae p 2 and p 3 stronger in older stages.

Gnathosoma ( Figs 5 B, 6B, 7B). Subcapitular setae a, m and h setiform, smooth, distinctly shorter in larva and deutonymph than those in tritonymph. Adoral setae short, thin, smooth. Palp with setation 0–1–1–3–9(+ω) in larva and 0–2–1–3–9(+ω) in nymphs. Solenidion (ω) of palptarsus thickened, straight, blunt-ended. Chelicera with two setiform setae, cha longer than chb. Trägårdh’s organ (Tg) inconspicuous.

Epimeral region ( Figs 5 B, 6B, 7B). Epimeral setae simple, thin, smooth, without cerotegument; seta 1b in larva inserted on distinct tubercle; setae 1b and 3b in deutonymph distinctly longer than other setae, and 3c, 4a and 4b slightly longer than other setae. Setal formula of epimeres of larva: 2–1–2, third seta (1c, not included in formula) of the first epimere forms protective scale over Claparède’s organ; deutonymph: 3–1–2–2; tritonymph: 3– 1–3–3.

Ano-genital region ( Figs 5 B, 6B, 7B). Genital papillae of deutonymph different in size and shape, but similar in tritonymph. Three pairs of genital, one pair of aggenital and three pairs of adanal setae in deutonymph; five pairs of genital, two pairs of anal setae in tritonymph. All genital, aggenital, anal and adanal setae thin, smooth. Cupules iad, ih, ip and ips appearing in normal ontogenetic pattern.

Legs. Most setae of legs long, finely barbed except short and smooth setae p. Tibia I with dorsal apophysis bearing very long, flagellate solenidion φ1 and its coupled seta d. Tibiae II, III and genia I–III with coupled setae d and respective solenidia. Famulus regressive, sunken, submerged in fovea with sclerotized, cup-like elevated rim. Formulas of leg setation for larva: I (0– 2 –3–4–16), II (0– 2 –3–3–13), III (0– 2 –2–3–13), formula of solenidia: I (1– 1–1), II (1–1–1), III (1–1–0); deutonymph: I (1–4–4–5–16), II (1–4–4–4–13), III (2–3–3–4–13), IV (1–2–3–3–12), formula of solenidia: I (1–2–2), II (1–1–2), III (1–1–0); IV (0–1–0); tritonymph: I (1–5–4–5–18), II (1–4–4–5–15), III (2–3–3–4–15), IV (1–3–3–4–12), 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 1 .

Material examined. Holotype (male): Khuitnii-Am area, Mts. Mongol Altai, close to Lake Dayan, District Sagsai, Province Bayan-Ulgii, foliose and subfruticose lichens growing on larch tree barks ( Larix sibiricus Ledebour, 1833 ), N48o14’, E88o55’, elevation 2356 m a.s.l., 18 July 2010, Col. B. Bayartogtokh; 16 paratypes (10 females and six males): same data as holotype, but 11 specimens were found in lichens growing on tree trunks, while five of them in lichens growing on bare rocks. Three larvae, one deutonymph and one tritonymph: same data as adults. The holotype and 10 paratypes are deposited in the collection of the Department of Biology, National University of Mongolia, Ulaanbaatar, and six paratypes are in the collection of the Senckenberg Museum of Natural History, Goerlitz. The immatures are preserved in the collection of Department of Biology, National University of Mongolia. All type specimens are preserved in alcohol.

Remarks. Adults of Epidamaeus munkhbayari sp. nov. can be readily distinguished form all other known species of Epidamaeus in having the combination of 1) the two pairs of well-developed prodorsal ridges; 2) the presence of ventral tubercles E2a, Va and Vp on epimeral region; 3) the short, thin interlamellar seta; 4) the welldeveloped tectum of podocephalic fossa laterally produced as relatively short subtriangular tooth. As far as we know, the presence of two pairs of semicircular ridges on prodorsum is unknown in Epidamaeus , which makes the present new species clearly different from the others.

Larvae and nymphs of this new species differ from those of other species of Epidamaeus , the immature morphology of which is known, by the 1) relatively short sensillii (nearly twice shorter) as opposed to the very long sensilli in juveniles of the other species; 2) smooth gastronotic setae lp in contrast to the distinctly barbed setae in juveniles of the other species, and 3) relatively larger body size of larva and nymphs (see Table 3).

Etymology. The present species is named in honor of Dr. Khorloo Munkhbayar, professor emeritus of the Department of Biology, Mongolian State University of Education, on the occasion of his 75th birthday. His superb teaching and enthusiasm for zoology and ecology influenced the lives and careers of many students.

Distribution and habitat ecology. Currently this species is known only from the type locality, Mongol Altai mountains in western Mongolia, where cool temperate coniferous forests with alpine vegetation grow. Both the adults and immature of this species have been found in foliose or subfruticose lichens growing on bare rocks ( Xantoria candelaria , Melanelixia exasperatula , Parmelia sulcata ) and fruticose lichens ( Usnea sp.) growing on larch trees. This finding is indicated that E. munkhbayari sp. nov. inhabits and feeds on lichens growing on trees as well as bare rocks.

Figures

FIGURE 1. Adult of Epidamaeus munkhbayari sp. nov. (A) Dorsal view, legs partly shown; (B) Sensillus and bothridium; (C) Ventral view, legs partly shown; (D) Lateral view, seta 3 a not shown, without legs.

FIGURE 2. Adult of Epidamaeus munkhbayari sp. nov. (A) Leg I, right, antiaxial view; (B) Leg II, right, antiaxial view; (C) Genu, tibia and tarsus of leg III, right, antiaxial view; (D) Trochanter and femur of leg III, right, antiaxial view.

FIGURE 3. Adult of Epidamaeus munkhbayari sp. nov. (A) Tarsus of leg IV, right, antiaxial view; (B) Genu and tibia of leg IV, right, antiaxial view; (C) Trochanter and femur of leg IV, right, antiaxial view (slightly twisted); (D) Chelichera, right, antiaxial view; (E) Palp, right.

FIGURE 4. Adult of Epidamaeus munkhbayari sp. nov., compound microscope images (not to scale). (A) Part of prodorsum showing anterior dorsal rigde (indicated by arrow) and insertion of lamellar setae; (B) Part of epimeral region showing epimeral and ventral enantiophyses; (C) Part of epimeral region showing tectum of podocephalic fossa (t) and epimeral seta 1 c; (D) Anterior part of notogaster and posterior part of prodorsum showing spinae adnatae, setae in and ss; (E) Postbothridial tubercle Ba; (F) Distal part of sensillus covered with conglomerate of cerotegument; (G) Part of prodorsum showing posterior dorsal rigde (indicated by arrow), bothridium and insertion of interlamellar setae; (H) Lateral view of posterior part of prodorsum showing dorsal rigdes (indicated by arrows).

FIGURE 5. Larva of Epidamaeus munkhbayari sp. nov. (A) Dorsal view, legs partly shown; (B) Ventral view, legs partly shown.

FIGURE 6. Deutonymph and protonymphal exuvial scalp of Epidamaeus munkhbayari sp. nov. (A) Dorsal view, legs partly shown; (B) Ventral view, legs partly shown; (C) Protonymphal exuvial scalp.

FIGURE 7. Tritonymph of Epidamaeus munkhbayari sp. nov. (A) Dorsal view, legs partly shown; (B) Ventral view, legs partly shown.

Tables

TABLE 1. Ontogeny of setae and solenidia of Epidamaeus munkhbayari sp. nov. (Structures are indicated where they are first added and are assumed present through the rest of ontogeny, unless noted otherwise; setae in parentheses represent pairs; dash indicates no additions).

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