Oromurcia magadanensis, Ermilov & Makarova & Behan-Pelletier, 2022

Ermilov, Sergey G., Makarova, Olga L. & Behan-Pelletier, Valerie M., 2022, Description of Oromurcia magadanensis sp. nov. (Acari, Oribatida, Ceratozetidae) from Russia, with remarks on biogeography of the genus Oromurcia Thor, 1930, Zootaxa 5187 (1), pp. 30-52 : 32-44

Oromurcia magadanensis sp. nov.

Diagnosis. Adult. Body length: 514–581. Rostrum truncate, with one pair of small lateral teeth; rostral region with median bulge and one pair of slight, longitudinal furrows. Lamellar cusp with strong lateral tooth. Translamella absent. Rostral (82–86), lamellar (98–102) and interlamellar (135–143) setae setiform, barbed. Bothridial seta short (36–41), clavate, broadly rounded distally, barbed. Four pairs of small, round notogastral porose areas. Ten pairs of notogastral setae comparatively short, setiform, barbed; c, la, lm, lp (45–53) longer than h 1 – h 3 (32–36) and p 1 – p 3 (24–28). Pedotectum I concave dorsally. Epimeral and anogenital setae setiform, barbed. Juvenile instars. Rostral, lamellar and interlamellar setae long, setiform, barbed; in longest. Bothridial seta short, clavate, barbed. Humeral organ present in all immature instars, porose. Gastronotic shield well developed only in nymphs. Dorsal gastronotic setae of medium-sized in larva versus da and dm (and dp in tritonymph) short in nymphs, all setiform, barbed; c 3 and dp longest in larva, c 3, dp and h 3 longest in protonymph, c 3 and h 1 longest in deutonymph, c 3 longest in tritonymph. Epimeral and anogenital setae setiform, barbed.

Adult

( Figs 1–4 )

Measurements. Body length: 564 (holotype, female), 514–531 (four male paratypes), 531–581 (12 female paratypes); notogastral width: 381 (holotype), 348–398 (four male paratypes), 365–398 (12 female paratypes).

Integument ( Figs 3F , 4F ). Body colour brown. Body surface microsculpturing tuberculate (visible in dissected specimens under 10 × 100 magnification).

Prodorsum ( Figs 1A, 1C , 3A, 3C, 3D , 4A–C ). Rostrum truncate, with one pair of small lateral teeth. Rostral region with median bulge and one pair of slight, longitudinal furrows (directed to rostral teeth). Lamella (including cusp) about 1/2 length of prodorsum; cusp short, with large or small lateral tooth (6–12). Translamella absent. Tutorium (including cusp) about 3/4 length of prodorsum; cusp broad, with several (up to seven) small teeth. Porose area Al not observed. Genal tooth strong, elongate triangular. Rostral (82–86), lamellar (98–102) and interlamellar (135–143) setae setiform, barbed; basal part of ro not covered by tutorium. Bothridial seta (36–41) clavate (may seem globular in dorsal view), broadly rounded distally, slightly barbed; stalk shorter than head. Bothridium covered or not by anterior margin of notogaster in dorsal aspect. Exobothridial seta (20–24) setiform, thin, slightly barbed. Dorsosejugal porose area oval, poorly visible. Dorsophragmata separated medially.

Notogaster ( Figs 1A, 1C, 1D , 3A, 3D, 3E , 4D, 4E ). Lenticulus not observed. Pteromorph broadly rounded laterally. Four pairs of rounded porose areas (Aa: 16–24; A1, A3: 12–16; A2: 6–8). Ten pairs of notogastral setae (c, la, lm, lp: 45–53; h 1 – h 3: 32–36; p 1 – p 3: 24–28) setiform, barbed; often p 2 and p 3 thinner than others. Opisthonotal gland opening and all lyrifissures distinct.

Gnathosoma ( Figs 2A–C ). Subcapitulum size: 123–135 × 90–98. Subcapitular (a: 24; m: 36–41; h: 28–32) and adoral (12–14) setae setiform, barbed. Palp (131–135) setation: 0–2–1–3–9(+ω). Postpalpal seta (8) spiniform.Axillary saccule (8) distinct, oblong. Chelicera (131–143) with two setiform, barbed setae (cha: 41–49; chb: 28–32).

Lateral podosomal and epimeral regions ( Figs 1B, 1C , 3B , 4F ). Humeral porose areas Am and Ah oval. Pedotectum I concave dorsally. Custodium short, narrowly triangular. Discidium broadly triangular. Circumpedal carina long, apically fused to custodium. Horizontal folds in integument observed between and dorsal of acetabula II and III. Epimeral setal formula: 3-1-3-3. Epimeral setae (1a, 2a, 3a: 20–24; others: 24–32) setiform, barbed.

Anogenital region ( Figs 1B–D , 3B, 3C, 3E , 4F, 4G ). Six pairs of genital (20–24), one pair of aggenital (24–32), two pairs of anal (24–32), and three pairs of adanal (24–32) setae setiform, barbed. Adanal lyrifissure located close and parallel to anal plate. Postanal porose area (102–110 × 4–6) band-like.

Legs ( Figs 2D–G , 3B, 3C ). Median claw distinctly thicker than lateral claws, all slightly barbed dorsally. Dorsoparaxial porose area on femora I–IV and on trochanters III, IV distinct. Proximoventral porose area on tarsi I–IV and distoventral porose area on tibiae I–IV present, weakly visible. Small indistinct porose regions proximal to insertions of paired setae p and u located dorsally and ventrally on tarsi I–IV. Genua I–IV without lateral tubercle and ventral triangular process. Formulas of leg setation and solenidia: I (1-5-3-4-20) [1-2-2], II (1-5-3-4-15) [1-1-2], III (2-2-1-3-15) [1-1-0], IV (1-2-2-3-12) [0-1-0]; homology of setae and solenidia as indicated in Table 1 . Famulus short, stick-like, slightly swollen distally, inserted between solenidia ω 1 and ω 2. Seta s on tarsus I eupathidial, located between paired setae u and a. Seta l’ on femur III absent. Lateral antiaxial seta (l” on legs I, II; l’ on legs III, IV) on tibiae I, II and on genua I–III thick; on tibiae III, IV and genu IV thickened. Solenidia ω 1 and ω 2 on tarsus II and σ on genu III rod-like, other solenidia setiform. Solenidion φ 2 on tibia I located on dorsodistal tubercle distal of solenidion φ 1.

Juvenile instars

( Figs 5–10 )

Measurements. Total length of larva: 249–265 (n=4), protonymph: 265–282 (n=6), deutonymph: 298–348 (n=9), tritonymph: 381–514 (n=9). Total width of larva: 116–132 (n=4), protonymph: 132–165 (n=6), deutonymph: 182– 199 (n=9), tritonymph: 215–315 (n=9).

Integument ( Figs 10F–H ). Body colourless to pale yellow and light brown. Cuticle densely microporose. Anogenital region and lateral side of body with some folds.

Prodorsum ( Figs 5A, 5B , 6A, 6B , 8A , 10A–E ). About 1/2 length of gastronotic region. Rostrum slightly narrowed in larva versus broadly rounded in nymphal instars. Rostral, lamellar and interlamellar setae setiform, barbed. Exobothridial seta setiform, thin, slightly barbed. Bothridial seta clavate, slightly barbed. Prodorsal setae lengths during ontogeny are presented in Table 2 .

Gastronotic region ( Figs 5A, 5B , 6A, 6B , 7A–C , 8A, 8B , 10A–E, 10H ). Humeral sclerites absent. Gastronotic shield (macrosclerite) distinct in nymphal instars versus not observed in larva. Humeral organ present, positioned anterolateral or lateral to seta c 3. Larva with 12 pairs, nymphs with 15 (of these, 10 pairs located on macrosclerite) pairs of setiform, barbed setae; in all nymphs, setae p 1, and p 2 (also da, dm, dp in tritonymph) thinner than others. Gastronotic setae lengths during ontogeny are presented in Table 2 . One pair of slightly pigmented, small, round pits (? rudimentary porose areas Aa) located between and ventral of setae c 1 and c 2. Cupules ia, im and ip and opisthonotal gland opening well visible.

Gnathosoma ( Figs 9A–C , 10G ). Generally similar to adult except: labiogenal articulation of subcapitulum not developed; subcapitular setae equal in length, all slightly barbed.

Epimeral region ( Figs 6A, 6B , 7A–C , 8B , 10G ). Setal formulas for successive epimeres: larva 3-1-2 (third setae of first epimere forms protective scale over respective Claparède’s organ); protonymph 3-1-2-1; deutonymph 3-1-2-2, tritonymph 3-1-3-3. Setae setiform, slightly barbed. Epimeral setae lengths during ontogeny are presented in Table 2 .

Anogenital region ( Figs 6A, 6B , 7A–C , 8B , 10H ). Ontogeny of genital, aggenital, adanal, and anal setal formulas, larva to tritonymph: 0-1-3-5, 0-0-1-1, 0-0-3-3, 0-0-0-2, respectively.All setae setiform, slightly barbed. Cupules ih, ips, iad appearing in normal ontogenetic pattern. Anogenital setae lengths during ontogeny are presented in Table 2 .

Legs ( Figs 9D–F , 10A–C ). Claw of each leg strong, slightly barbed dorsally. Ventroparaxial porose area on femora I-IV distinct. Porose area on trochanters III, IV, proximoventral porose area on tarsi I-IV and distoventral porose area on tibiae I-IV not observed. Leg formulas: larva: I (0–2–2–3–16) [1–1–1], II (0–2–2–2–13) [1–1–1], III (0–2–1–1–13) [1–1–0]; protonymph: I (0–2–2–3–16) [1–1–2], II (0–2–2–2–13) [1–1–1], III (0–2–1–1–13) [1–1–0], IV (0–0–0–0–7) [0–0–0]; deutonymph: I (0–4–2–3–16) [1–2–2], II (0–4–2–3–13) [1–1–2], III (1–2–1–1–13) [1– 1–0], IV (0–2–2–1–12) [0–1–0]; tritonymph: I (1–4–3–4–18) [1–2–2], II (1–4–3–4–15) [1–1–2], III (2–2–1–3–15) [1–1–0], IV (1–2–2–3–12) [0–1–0]. Homologies of leg setae and solenidia as indicated in Table 1 .

Material examined. Holotype (female), 16 paratypes (four males, 12 females) and 28 juvenile instars (four larvae, six protonymphs, nine deutonymphs, nine tritonymphs): Northeast Asia, Russia, Magadan Region, upper reaches of the Ola River , Ola Plateau , 60°39’ N, 151°16’ E, 1023 m a.s.l., rocky slope of a snowbed in the narrow stream gully, planted by Oxyria digyna , Artemisia kruhsiana , Ranunculus pygmaeus , Saxifraga cernua , S. hyperborea , Sanionia uncinata , 11.08.2011 (leg. O.L. Makarova) (see Fig. 11 ). The gut of some specimens contains a tangle of micromycete hyphae.

Type deposition. The holotype and two paratypes are deposited in the collection of the SMNH; 16 paratypes and all juvenile instars are deposited in the collection of the TSUMZ. All specimens are preserved in 70% solution of ethanol with a drop of glycerol.

Etymology. The species name refers to the place of origin, Magadan region.

Differential diagnosis. Oromurcia magadanensis sp. nov. is morphologically very similar to O. bicuspidata Thor, 1930 and O. sudetica Willmann, 1939 . Adults of O. magadanensis sp. nov. differ from those of O. bicuspidata and O. sudetica (see Seniczak & Solhøy 1987, Seniczak & Seniczak 2011; Weigmann 2006) by the smaller size (length 510–580 versus 570–725), bothridial seta broadly rounded distally (versus fusiform, narrowed distally or weakly clavate), dentate tutorium (versus smooth), and absence of striations on the lamella. It differs from O. sudetica in porose area A1 laterally positioned in longitudinal alignment with Aa and A2 (versus A1 more medially positioned). Juvenile instars of O. magadanensis sp. nov. differ from those of O. bicuspidata and O. sudetica (see Seniczak & Solhøy 1987; Seniczak & Seniczak 2011) by the presence of medium-sized (versus comparatively short) gastronotic setae с 1, c 2, da, la, dm, lm in larva, and long (versus short) lateral and posterior gastronotic setae especially с 3, lm, lp, h 1, h 3 in nymphs.

Oromurcia magadanensis sp. nov. also is morphologically similar to Svalbardia lucens (L. Koch, 1879) . Adults of O. magadanensis sp. nov. differ from those of S. lucens (see Hammer 1952 b; Behan-Pelletier 1985; Seniczak 1993; Ermilov et al. 2022) by the presence (versus absence or indistinct development) of a well-developed lateral tooth on lamellar cusp. Tritonymph of O. magadanensis sp. nov. differs from that of S. lucens (see Behan-Pelletier, 1985; Seniczak 1993; Ermilov et al. 2022) by the presence of short (versus comparatively long) gastronotic seta dp, and the absence (versus presence) of microsclerites at the base of setae c 1, c 2, c 3, p 2, p 3.

Ontogenetic transformations of Oromurcia magadanensis sp. nov.

Juveniles unpigmented, colourless to pale yellowish and light brown; adult brown. Cuticle microporose, with some folds on lateral sides of body in juvenile instars; microsculpturing tuberculate in adult. Prodorsum with five pairs of prodorsal setae (including bothridial seta) constant during ontogeny; all these setae slightly elongated during ontogeny. Bothridial seta with short stalk and clavate head. Humeral region present in larva and all nymphal instars. Gastronotic shield (macrosclerite) not observed in larva, distinct in nymphs, absent in adult. Larva bears 12 pairs of gastronotic setae, whereas in protonymph the setae of p -series are newly appeared; hence, nymphal instars bear 15 pairs of gastronotic setae, while the adult has 10 (da, dm, dp, and two pairs of setae of c series lost) pairs of notogastral setae. In larva, dorsal gastronotic setae approximately equal in length; in nymphs, setae da and dm (and dp in tritonymph) distinctly shorter than other dorsal gastronotic setae; in adult, setae slightly differ in length. Larva has six pairs of epimeral setae (1a, 1b, 1c, 2a, 3a, and 3b), and in protonymph, seta 4a appears, seta 4b added in deutonymph, setae 3c and 4c formed in tritonymph. Number of anogenital setae gradually increasing from protonymph to adult; a pair of genital setae are formed first in protonymph; three pairs of genital, one pair of aggenital and three pairs of adanal setae present in deutonymph; tritonymph possessed five pairs of genital setae and two pairs of anal setae. Except for genital setae (six pairs in adult), the anogenital setation of tritonymph remaining the same in the adult instar. Paraproctal valves of larva (segment PS), protonymph (segment AD) and deutonymph (segment AN) without setae. Leg setation increasing based on instar to instar as shown in Table 1 .

We compare ontogenetic data for the three described species of Oromurcia with those known for other members of the subfamily Trichoribatinae with arctic or alpine ranges in Table 3 , based on the ontogenetic data table of Bayartogtokh & Ermilov (2016). We do not include data of species with boreal distribution, i.e., Dentizetes ledensis Behan-Pelletier, 2000 , or temperate species, e.g., Jugatala tuberosa Ewing, 1913 and Trichoribates incisellus ( Kramer, 1897) , or tropical species, e.g., Trichoribates ocotlicus Palacios-Vargas & Norton, 1984 and T. tepetlensis Palacios-Vargas & Norton, 1984 .

We emend Bayartogtokh & Ermilov (2016) as follows: genital setal ontogeny of Umbellozetes slaveki is 0-1- 2-5-6 ( Seniczak & Seniczak 2011); Seniczak & Solhøy (1987) gave genital setal ontogenies (larva to adult) of 0-1- 3-5-6 for Oromurcia bicuspidata and O. sudetica ; humeral organ in immatures is illustrated for U. slaveki and O. bicuspidata by Seniczak & Seniczak (2011).

Shaldybina (1966, 1974, 1977) included the genera Diapterobates Grandjean, 1936 , Humerobates Sellnick, 1928 , Latilamellobates Shaldybina, 1971 , Oromurcia , Propelops Jacot, 1937 , Svalbardia , and Trichoribates Berlese, 1910 in the subfamily Trichoribatinae . Subsequently, based on character states of immatures, Humerobates was moved to Humerobatidae ( Grandjean 1970; Weigmann 2006), Propelops to Phenopelopidae ( Norton & Behan-Pelletier 1986) , and Latilamellobates was placed in synonymy with Trichoribates ( Weigmann 2006) . Genera Dentizetes Hammer, 1952 (in 1952 a), Iugoribates Sellnick, 1944 , Jugatala Ewing, 1913 , and Umbellozetes Krivolutsky, 1969 (in Zlotin & Krivolutsky 1969) were included in Trichoribatinae ( Bayartogtokh & Ermilov 2016). We include Neogymnobates Ewing, 1917 as well, based on the studies of N. luteus ( Hammer, 1955) by Behan-Pelletier (1986).

Figures

FIGURE 1. Oromurcia magadanensis sp. nov., adult:A—dorsal view (legs not shown); B—ventral view (gnathosoma and legs not shown); C—lateral view (gnathosoma and legs not shown); D—posterior view. Scale bar 100 μm.

FIGURE 2. Oromurcia magadanensis sp. nov., adult: A—subcapitulum, ventral view; B—palp, right, antiaxial view; C—chelicera, left, paraxial view; D—leg I, right, antiaxial view; E —leg II (tarsus not shown), right, antiaxial view; F—leg III (tarsus not shown), left, antiaxial view; D—leg IV, left, antiaxial view. Scale bars 50 μm (A, C–G), 20 μm (B).

FIGURE 3. Oromurcia magadanensis sp. nov., adult, SEM micrographs: A—dorsal view; B—ventral view; C—ventrolateral view; D—dorsoanterior view; E—posterior view; F—notogastral tuberculate microsculpturing.

FIGURE 4. Oromurcia magadanensis sp. nov., dissected adult, microscope images: A—lamellar cusps, dorsal view; B—anterior part of prodorsum, lateral view; C—dorsophragmata; D—notogastral porose area Aa; E—notogastral seta lm; F genital plates and part of epimeral and lateral podosomal region, ventral view; G—part of anoadanal region.

FIGURE 5. Oromurcia magadanensis sp. nov., juvenile instars: A—larva, dorsal view; B—protonymph, dorsal view. Scale bar 50 μm.

FIGURE 6. Oromurcia magadanensis sp. nov., juvenile instars: A—larva, lateral view; B—tritonymph, lateral view. Scale bar 50 μm. Scale bars 50 μm (A), 100 μm (B).

FIGURE 7. Oromurcia magadanensis sp. nov., ventral side of juvenile instars (legs and anterior part of body not shown): A—larva; B—protonymph; C—deutonymph. Scale bars 50 μm.

FIGURE 8. Oromurcia magadanensis sp. nov., tritonymph: A—dorsal view; B—ventral view (legs and anterior part of body not shown). Scale bar 100 μm.

FIGURE 9. Oromurcia magadanensis sp. nov., larva: A—subcapitulum, ventral view; B—palp, right, antiaxial view; C—chelicera, left, paraxial view; D—leg I, left, paraxial view; E—leg II, left, paraxial; F—leg III, left, antiaxial view. Scale bars 10 μm (A–C), 20 μm (D–F).

FIGURE 10. Oromurcia magadanensis sp. nov., SEM micrographs of slightly deformed deutonymph (A–C) and microscope images of dissected juvenile instars (D–H): A, B—dorsal view; C—lateral view; D—larva, dorsal view; E—tritonymph, basal part of prodorsum and anterior part of gastronotum (pigmented, small, round pit (? rudimentary porose area Aa) is indicated by an arrow), dorsal view; F—tritonymph, some setae on gastronotic macrosclerite, dorsal view; G—protonymph, anterior part of body, ventral view; H —protonymph, posterior part of body, ventral view.

FIGURE 11. Collecting place of Oromurcia magadanensis sp. nov.: A—landscape of the Ola Plateau, Magadan Region, 60°39’ N, 151°16’ E; B—snowbed in the stream gully (the place of collection, 1023 m a.s.l., is indicated by an yellow arrow); C, D—rocky slope of a snowbed with vegetation patches dominated by Oxyria digyna and Artemisia kruhsiana (C) or Ranunculus pygmaeus and Sanionia uncinata (D).