Sibiriulus mikhaljovae Nefediev & Nefedieva, 2020

Nefediev, Pavel S., Nefedieva, Julia S. & Krugova, Tatiana M., 2020, The millipede genus Sibiriulus Gulička, 1963 revisited, with the description of a new species from the Altais, southwestern Siberia, Russia (Diplopoda: Julida Julidae), Zootaxa 4869 (3), pp. 421-429 : 422-426

Sibiriulus mikhaljovae Nefediev & Nefedieva sp. nov.

Figs 1–16

Sibiriulus sp. 1— Krugova & Nefediev 2018: 116; Krugova et al. 2018: 337.

Name. Honours Mrs Elena V. Mikhaljova, a prominent Russian diplopodologist who has made great contributions to the knowledge of the millipede faunas of Asia. Noun in the genitive case.

Material examined. Holotype: male ( ZMUM Rd 4669), Russia, southwestern Siberia, Altai Province, Krasnoshchiokovo District, 3 air-km NW of Tigirek, buffer zone of Tigirek State Nature Reserve, Logovo Gieny Cave, 51.16610°N, 82.99532°E, ca. 690 m a.s.l., near cave entrance, bush forested steppe with Caragana arborescens and Spiraea , under stones and in litter, 7 June 2020, collected by P.S. Nefediev.

Paratypes: 1 male, 1 female, 6 subadult males, 6 subadult females, 3 juveniles ( ZMUM Rd 4670), together with holotype, 7 June 2020, collected by P.S. Nefediev; 1 male ( ASU, permanent microscopic slide with antenna, gnathochilarium, leg-pairs 1 and 2, promere and remaining gonopods), Russia, southwestern Siberia, Altai Province, Krasnoshchiokovo District, 6 air-km NW of Tigirek, Tigirek State Nature Reserve, Khankhara site, left bank of Dragunskii Brook, 51.188433°N, 82.976150°E, ca. 910 m a.s.l., middle part of S slope, mixed herbaceous steppe with Helictotrichon , Carex and Spiraea bushes, pitfall traps, 15–25 August 2015, collected by T.M. Krugova, E. V. Nosova and Yu.B. Ostanina; 1 male, 2 females ( ASU), Russia, Altai Province, Krasnoshchiokovo District, 6 airkm NW of Tigirek, Tigirek State Nature Reserve, Khankhara site, left bank of Dragunskii Brook, 51.188525°N, 82.976403°E, 900 m a.s.l., upper part of S slope, steppe meadow, soil sample, 17 August 2016, collected by T.M. Krugova, V. V. Zelenskii, R. V. Shcherbakova, L.Yu. Gruntova, K. V. Smirnova, A.E. Pupkova and M.N. Terioshkina; 1 male, 1 female ( FSCB), 1 male, 1 female, 1 subadult male, 1 subadult female ( ASU), Russia, southwestern Siberia, Altai Province, Krasnoshchiokovo District, 2.5 air-km N of Tigirek, buffer zone of Tigirek State Nature Reserve, Strashnaya Cave, 51.170746°N, 83.020825°E, 530 m a.s.l., near cave entrance, bush thicket with C. arborescens , Lonicera tatarica and Spiraea , under stones and in litter, 19 August 2016, collected by P.S. Nefediev and J.S. Nefedieva; 1 male, 1 fragment ( ASU), Russia, southwestern Siberia, Altai Province, Kuria District, 7.5 air-km NW of Tigirek, buffer zone of Tigirek State Nature Reserve, S slope of Chiornyi Kamen Mt, 51.18718°N, 82.94439°E, ca. 890 m a.s.l., stony steppe with sparse Larix sibirica , under stones, 18 May 2019, collected by P.S. Nefediev and P. V. Golyakov; 1 female ( ASU), Russia, southwestern Siberia, Altai Province, Kuria District, 7.5 air-km NW of Tigirek, buffer zone of Tigirek State Nature Reserve, S slope of Mt Chiornyi Kamen, 51.18609°N, 82.94550°E, ca. 850 m a.s.l., stony steppe, under stones, 18 May 2019, collected by P.S. Nefediev; 1 subadult female, 1 juvenile ( ASU), Russia, southwestern Siberia, Altai Province, Krasnoshchiokovo District, 3 air-km NW of Tigirek, buffer zone of Tigirek State Nature Reserve, Logovo Gieny Cave, 51.16610°N, 82.99532°E, ca. 690 m a.s.l., near cave entrance, bush forested steppe with Caragana arborescens and Spiraea , under stones and in litter, 16 May 2020, collected by P.S. Nefediev and J.S. Nefedieva.

Diagnosis. Differs from congeners mainly by the configuration of the apex of the gonopod mesomere that shows the presence of a longitudinal crest inside the apical fovea.

Description. Male. Length of holotype 14.6 mm, vertical diameter 0.75 mm, with 45(–3) body segments, excluding telson, or 42+3+T; length of paratypes 13.7–15 mm, vertical diameter 0.75–0.80 mm, with 43(–2), 44(–3), 45(–2), 46(–2) body segments, excluding telson, or 41+2+T, 41+3+T, 43+2+T, 44+2+T in paratypes. Body coloration brown to pale brown ventrally. Head with a marbled region on clypeus around and a pair of pale brown spots between antennal sockets, frons dark brown, epicranium marbled brown. Collum marbled brown with a distinct, dark brown, transverse band along fore margin and with a thin dark brown band along its rear edge. Postcollar terga with a thin dark brown axial stripe. Metazonites with dark brown transverse bands, prozonites paler, with brown spots close to venter. Antennae dark brown, eye-patches black. Legs pale brown.

Ocular fields as a Reuleaux triangle, each composed of 23+23 to 32+32 slightly convex ommatidia, arranged in 7 rows. Epicranial setae 1+1, supralabral setae 2+2, both arranged in a transverse row, labral setae 5+6, 6+6, 7+7, 7+8, 8+8, 9+9. Labrum tridentate. Antennae medium-sized, extending past segments 4–5 when stretched dorsad. Length and width ratios of antennomeres 2–7 varying from specimen to specimen, e.g. length ratios as 2.9:2.1:1.4:2.1:1.3:1 or 3.6:3:2.6:3.4:2:1, width ratios as 1.2:1.4:1.4:2:1.4:1 or 1:1.1:1.3:1.6:1.4:1, respectively. However, the most common situation being as follows: in length, antennomere 2>5≥3>4>6>7, while in width, antennomere 5>6≥4≥3>2≥7 ( Fig. 1 ). At least 7 and 10 sensilla basiconica bacilliformia in a distodorsal corolla on each of antennomeres 5 and 6, respectively. Antennomere 7 with a terminal corolla of small sensilla basiconica bacilliformia ( Fig. 2 ). Gnathochilarium distally with two setae at outer edge of each stipes, with one seta closer to medial portion, a micropapillate low knob and a group of 4–8 non-apical, short, stipital setae. Each lamella lingualis with at least two long setae arranged longitudinally: one seta closer to tip, the other in medial portion ( Fig. 3 ); additionally, 1–2 short setae closer to promentum ( Fig. 4 ). Promentum short, subdiamond shaped. Genae unmodified. Collum covered with short longitudinal notches across the surface, with or without sparse striations laterally.

Body subcylindrical, slender, somewhat compressed laterally. Pro- and metazonites separated by a distinct suture. Prozonites smooth. Metazonites with striae reaching the rear margin only ventrally; 4–10 striae on metazonital surface between dorsal axial stripe and ozopore, increasingly dense towards telson. Transverse row of sparse, thin, relatively short setae at hind edge of metazonites. Metazonital setae gradually growing longer and denser towards telson. Ozopores small, lying behind suture between pro- and metazonites, but without touching it. Epiproct subcylindrical, with a tiny claw-shaped process directed caudad and somewhat ventrad. Telson covered with sparse and relatively long setae. Paraprocts densely setose. Hypoproct subtriangular, setose only along caudal margin.

Starting with leg-pair 2, male walking legs slender, with very delicately serrate sole pads (sp) on tibiae and postfemora, gradually reduced towards posterior body end to totally disappear on last legs ( Figs 6 , 7 ). Tarsal claw at base with a seta (ts) ventrally ( Fig. 6 ). Leg-pair 1 unciform, with low papillae apically and 2-segmented telopodites carrying strong setae ventrally: telopoditomeres 1 and 2 with four or 3–4 setae, respectively. Telopoditomere 2 with a rounded, low, knob-shaped protuberance (kp) ventrally ( Fig. 5 ). Each coxa of leg-pair 1 with a distal seta. Leg-pair 2 unmodified ( Fig. 6 ). Penes flattened, relatively short, doubled apically, without setae ( Figs 6 , 8 ). Male leg-pair 7 normal. Ventral margins of body segment 7 with rounded lobes in touch at midline.

Gonopods tripartite, each consisting of a pro-, a meso- and an opisthomere. Pro- and mesomere closely attached to each other, but opisthomere somewhat set off and shifted caudad. Meso- and opisthomere subequal in height, towering above promere ( Figs 13, 14 ). Promere flattened, caudally papillate nearly throughout, with small sublateral knob (sk) at base ( Fig. 9 ). Flagellum long, filiform distally. Mesomere slightly bent caudad, with a densely papillate plate frontally ( Fig. 10 ). Distal part of mesomere somewhat narrowed, hook-shaped, slightly bent forward; its apex carrying a fovea divided by a longitudinal crest (lc) ( Figs 10, 11 ). Opisthomere with a thin, styloid process (tp) on its ventral surface, located mesally behind solenomere, slightly bent caudad, as well as with a relief hookshaped projection (hp), pointed forward and somewhat dorsally, well visible only in lateral view. Lateral side of opisthomere with a fold, being a reduced phylacum (ph), terminating with rectangular protuberance (rp) caudodorsally. Parabasal part of opisthomere with an interior spine (s). Solenomere with an elongate and narrowed apex (as). A narrow membranous velum (v), with a pointed tip.

Female. Length 15.5–20 mm, vertical diameter 1–1.1 mm, with 44(–2), 45(–2), 47(–2) or 48(–2) body segments, excluding telson, or 42+2+T, 43+2+T, 45+2+T, 46+2+T. Eye-patches oviform, sometimes lemon-shaped, composed of 26+26 to 31+33 ommatidia. Labral setae 5+6, 6+6, 7+7, 8+9 or 9+9. Gnathochilarium devoid of non-apical stipital setae. Collum without striae. Leg-pairs 1 and 2 scarcely thicker than other legs. Other nonsexual characters as in male.

Vulvae oblong, with strong setae ( Figs 15, 16 ). Operculum higher than bursa; its apex with a subtriangular incision and at least 3 or 4 setae in each of two longitudinal rows, apical setae longest. Apical part of bursa with pair of hyaline lobes. Lateral and mesal bursal sclerites together with 5–8 setae. Posterior median sclerite of bursa with 13–15 setae arranged in two rows, apical setae longest.

Distribution. This species appears to occur only in the southern part of the Altai Province, southwestern Siberia, Russia within the Tigirek State Nature Reserve (Map). It seems to be one of the most narrowly localized Sibiriulus species among the known congeners.

Remarks. This species dwells mostly in steppe and bush habitats on open southern and eastern slopes at about 530–910 m a.s.l. Xerophilic. Endemic of the Russian Altais.

The following updated key can be proposed to Sibiriulus species (based on gonopodal characters alone and chiefly following Mikhaljova et al. (2014) and Mikhaljova (2017)).

1 (2) Apex of mesomere unmodified, simple................................................ Sibiriulus multinicus

2 (1) Apex of mesomere modified (with a fovea or protuberance, bent in hook-shape or narrowed in lateral view).......... 3

3 (8) Distal or middle part of opisthomere with a massive inner process........................................... 4

4 (5) Distal part of opisthomere bent anteriad at a nearly right angle; massive inner process of opisthomere placed near middle of its front surface................................................................ Sibiriulus rectangulus

5 (4) Distal part of opisthomere not bent anteriad at a nearly right angle; massive inner process of opisthomere placed in its distal part............................................................................................. 6

6 (7) Apex of mesomere arcuatedly broadened caudally and forming a protuberance.................. Sibiriulus profugus

7 (6) Apex of mesomere without protuberance, near hook-shaped.................................. Sibiriulus altaicus

8 (3) Distal or middle part of opisthomere without a massive inner process......................................... 9

9 (10, 11) Distal part of mesomere broad, almost straight, elongate ventrally; apical fovea of mesomere broad; distal part of opisthomere rounded along rear margin...................................................... Sibiriulus latisupremus

10 (9, 11) Distal part of mesomere broad, bent forward; apical fovea of mesomere with a longitudinal crest (lc); distal part of opisthomere not rounded along rear margin, with a rectangular protuberance (rp); lateral side of opisthomere with a small, relief, hook-shaped projection (hp) bent forward and dorsally....................... Sibiriulus mikhaljovae sp. nov.

11 (9, 10) Distal part of mesomere otherwise.................................................................... 12

12 (13) Distal part of mesomere neither nearly hook-shaped nor close to that; lateral side of opisthomere with a relief hook-shaped projection bent forward............................................................ Sibiriulus aktashensis

13 (12) Distal part of mesomere nearly hook-shaped; lateral side of opisthomere without a relief hook-shaped projection bent forward......................................................................... Sibiriulus baigazanensis

Figures

FIGURES 1–6. Sibiriulus mikhaljovae sp. nov., male paratypes. 1, antenna; 2, distal part of antenna; 3&4, gnathochilarium, ventral views; 5, leg-pair 1, anterior view; 6, leg-pair 2 and penes, posterior view. Abbreviations: kp, knob-shaped protuberance; p, penes; sp, sole pads; ts, tarsal seta. Scales: 100 μm (Figs 2, 5), 200 μm (Figs 1, 3–4, 6).

FIGURES 7–14. Sibiriulus mikhaljovae sp. nov., male paratypes. 7, distal part of leg-pair 2, posterior view; 8, penes; 9, gonopod promere, posterior view; 10, gonopod mesomere, anterior view; 11, mesomeral apex, anterior view; 12, gonopod opisthomere, anterior view; 13&14, gonopods, lateral and mesal views, respectively. Abbreviations: as, apex of solenomere; hp, hookshaped projection; lc, longitudinal crest; ph, phylacum; rp, rectangular protuberance; s, interior parabasal spine; sk, small knob; sp, sole pads; tp, thin, styloid process; ts, tarsal seta; v, velum. Scales: 50 μm (Figs 7, 8, 11), 100 μm (Figs 9, 10, 12–14).

FIGURES 15–21. 15&16, Sibiriulus mikhaljovae sp. nov., female paratype, vulva, posterior and lateral views, respectively; 17, Sibiriulus rectangulus Mikhaljova, 2009, topotype, leg-pair 2 and penes, posterior view; 18, distal part of leg-pair 2, posterior view; 19, Sibiriulus baigazanensis Mikhaljova, Nefediev & Nefedieva, 2014, gonopod promere, posterior view; 20, Sibiriulus aktashensis Mikhaljova, Nefediev & Nefedieva, 2014, gonopod promere, posterior view; 21, Sibiriulus latisupremus Mikhaljova, Nefediev & Nefedieva, 2014, gonopod promere, posterior view. Abbreviations: p, penes; sk, small knob; sp, sole pads. Scales: 100 μm (Figs 19–21 after Mikhaljova et al. 2014 with changes).