Omobrachyiulus ponticus Vagalinski, 2021

Vagalinski, Boyan & Golovatch, Sergei I., 2021, The millipede tribe Brachyiulini in the Caucasus (Diplopoda, Julida, Julidae), ZooKeys 1058, pp. 1-127 : 1

Omobrachyiulus ponticus Vagalinski sp. nov.

Figs 41 , 42 , 43

Material examined

(ZMUM). Holotype: ♂ (in head, collum to ring 3, ring 4 to ring 6, and rest of body; leg pair 1, penis, right leg 3, gonopods, left flange of pleurotergum 7, and a mid-body leg dissected) (ZMUM), Georgia, AR Abkhazia, Pitsunda-Myussera Nature Reserve, Myussera part, 20-130 m, mixed deciduous forest ( Castanea , Alnus , etc.), litter, under bark and stones, 8-10.IV.1983, SIG leg . Paratypes: 2 ♀♀ (one unbroken, the other in head to ring 3 and rest of body, right vulva dissected), same collecting data as of the holotype.

Diagnosis.

A species of Omobrachyiulus most similar to O. sevangensis (Lohmander, 1936) comb. nov., O. kvavadzei sp. nov., and O. trochiloides sp. nov.; sharing with O. Omobrachyiulus sevangensis and O. trochiloides sp. nov. the presence of a lamellar ridge-like anterior process of the opisthomere. Differs from the former species by the presence of a distinct, rounded, apicolateral part of the mesomeroidal lobe of the opisthomere, as well as by the solenomere considerably outreaching both anterior process and apical outgrowth of the basoposterior process, and from the latter species by the much more obscure, poorly differentiated basoposterior process ending in an unciform, rather than a fine rod-like, apical outgrowth. Resembling O. kvavadzei sp. nov. mostly by the promere having a distomesal lobe and by the mesomeroidal lobe of the opisthomere bearing an apicolateral part, but differing in other gonopod characters included in the tabular key to the Omobrachyiulus sevangensis group (Table 2 ).

Name.

After the Greek name of the Black Sea, Pontos Euxeinos, to emphasise the type locality of the new species at the eastern coast of that sea. Adjective.

Description.

Measurements: holotype ♂ in S VII, 35+1+T, L = 10 mm, H = 0.9 mm; paratype ♀♀ in S VII-VIII, 34-35+2+T, L = 11.5-12 mm, H = 1.2-1.35 mm.

Colouration (Fig. 41A ): Head and collum with the usual colour pattern; body gradually lighter from dorsal to ventral side; prozonae grey, dorsally with a transverse dark brown stripe near pro-metazonal suture; metazonae light brown-beige; dorsum with a continuous whitish axial line.

External structures: Eye patches in adults consisting of 20-23 relatively large, clearly convex ommatidia arranged in mostly easily recognisable vertical rows. Vertigial, supralabral, and labral setae: two, four, and 17, respectively. Antennae ca. 1.4 × as long as head in males and 1.1-1.15 × in females; antennomere 2> 5> 4 ≥ 3> 6. Gnathochilarium with a conspicuously large promentum separating lamellae linguales> halfway, the latter with three or four setae in a longitudinal row; stipites in males parabasally each with a longitudinal row of several setae, non-setose in females. Collum smooth, with a single deep groove running along entire lateral margin.

Body rings somewhat vaulted. Prozonae with scattered, very short and shallow, longitudinal grooves. Metazonae rather deeply striated, n Schub = 6 or 7; metazonal setae relatively short, ca. 2/5 of (in more anterior rings), to equal to (in more posterior rings), metazonal length, arranged in very dense whorls. Ozopores placed right in pro-metazonal suture in more anterior rings, and tightly behind suture in more posterior ones; sutures not being sinuous in front of ozopores. Tarsus of mid-body legs 1.3 × as long as tibia and 3.8 × as long as apical claw.

Telson (Fig. 41B ): Epiproct very long (considerably surpassing the longest paraproctal setae in males, somewhat less pronounced in females), straight, distally bent ventrad, ending with a pointed hyaline tip; with a few setae. Hypoproct in males narrowly trapezoidal, tridentate, the teeth blunt, protruding behind rear contour of paraprocts; the same being narrowly rounded in females. Paraprocts rather sparsely setose, without distinct row of shorter setae along caudal margins.

Male sexual characters: Mandibular stipites rather weakly expanded, forming a rounded ventro-anterior corner. Leg pair 1 (Fig. 42A ) considerably converging (turned against one another) hooks with slender tibial outgrowths. Leg pair 2 and following pairs with crested adhesive pads, both tibial and postfemoral ones gradually reduced towards telson, but still visible after mid-body; femora of pairs 3-7 with an oval groove in the centre of a bulge. Pleurotergum 7 ventrally forming broadly rounded lobes (Fig. 42B ) originating from the zone around pro-metazonal suture, protruding mesoventrad behind gonopods. Penis (42C) very small, subquadrate, without apical lobes and with very short, rounded, terminal lamellae directed distolaterad.

Gonopods (Fig. 43 ): Promere (Fig. 43B, p in Fig. 43A ) slightly exceeded in height by solenomere, slender, with nearly symmetrical mesal and lateral margins joining in a narrow, blunt apex; median ridge short and strongly pronounced; a well-developed distomesal lobe. Opisthomere slender; basoposterior process weakly pronounced, ending in a tapering apical outgrowth turned slightly anteriad; anterior process shaped as a micro-serrate lamellar ridge with a freely protruding, tapering, apical part; mesomeroidal lobe with a moderately pronounced basal part, flattened distally and ending in an apicolateral part being very similar in shape to that in O. kvavadzei sp. nov.; solenomere deeply divided into two fine, slender, parallel branches: an anterior and a posterior one, the latter being slightly longer than the former; spiniform filaments along flagellum channel either absent or too small and slanting to be detected by light microscopy.

Female sexual characters: Leg pairs 1 and 2 somewhat shorter, first also thicker, than following legs. Vulva (Fig. 42D, E ) rather slender, similarly shaped to that of O. kvavadzei sp. nov., the main difference being the less strongly slanting apex of bursa, and the smaller, apically positioned opening in O. ponticus sp. nov.; both bursa and operculum moderately densely covered with long setae. Receptaculum seminis consisting of a short finger-shaped central tube, and a long, spirally twisted, posterior tube ending in an ovoid posterior ampulla with a minute pocket at bottom.

General distribution.

SWGC.

Figures

Figure 39. Omobrachyiulus kvavadzei sp. nov., ♂ (A-F) and ♀ (H) paratypes from near mouth of Khekpara River, AR Ajara, Georgia, and ♂ paratype from Zeraboseli, AR Ajara, Georgia (ZMUM) (G) A hypoproct, ventral view B leg 7 C right flange of pleurotergum 7, ventro-lateral view D penis, caudal view E right gonopods, mesal view F right opisthomere, caudo-lateral view G distal part of right opisthomere, mesal view H right vulva, caudo-lateral view. Scale bars: 0.1 mm (A), 0.2 mm (B-H). Abbreviations: al apicolateral part of mesomeroidal lobe, ao apical outgrowth of basoposterior process, ct central tube, dt distal tip of anterior process f flagellum, op operculum, pa posterior ampulla, pt posterior tube s solenomere, sf spiniform filaments, si anteromesal sinus, tp proximal tip of anterior process.

Figure 40. Omobrachyiulus kvavadzei sp. nov., gonopods of ♂ paratype from near Chakhati, AR Ajara, Georgia (ZMUM) A left promere, caudal view (flagellum broken off near base) B right opisthomere (with flagellum in its channel), mesal view C left opisthomere, latero-caudal view D distal part of the same aspect E distal part of right opisthomere (with flagellum tip protruding out of its channel), mesal view. Scale bars: 0.1 mm (A-C), 0.05 mm (D, E). Abbreviations: al apicolateral part of mesomeroidal lobe, ao apical outgrowth of basoposterior process, ap anterior process, bpp basoposterior process, dml distomesal lobe, dt distal tip of anterior process, f flagellum, fc flagellum channel, g (supposed) gonocoxal gland, mg median groove, ml mesomeroidal lobe, mr median ridge, s solenomere, sf spiniform filaments, si anteromesal sinus, tp proximal tip of anterior process.

Figure 41. Omobrachyiulus ponticus sp. nov. A habitus of ♀ paratype, lateral, slightly dorsal view B telson of ♂ holotype, lateral view. Not to scale.

Figure 42. Omobrachyiulus ponticus sp. nov., ♂ holotype (A-C) and ♀ paratype (D, E) A leg pair 1, caudal view B left flange of pleurotergum 7, ventro-lateral view C penis, caudal view D right vulva, lateral view (receptaculum seminis seen by transparency, but drawn with solid lines for emphasis; setae omitted) E same, caudal view. Scale bars: 0.2 mm (D), 0.1 mm (A-C, E). Abbreviations: ct central tube, op operculum, pa posterior ampulla, pt posterior tube.

Figure 43. Omobrachyiulus ponticus sp. nov., gonopods of ♂ holotype A left gonopods, mesal view B right promere, caudal view C right opisthomere, mesal view D same, caudo-lateral view E distal part of the same aspect. Scale bars: 0.1 mm. Abbreviations: abs anterior branch of solenomere, al apicolateral part of mesomeroidal lobe, ao apical outgrowth of basoposterior process, ap anterior process, bpp basoposterior process, dml distomesal lobe, f flagellum, fc flagellum channel, ml mesomeroidal lobe, mr median ridge, p promere, pbs posterior branch of solenomere, s solenomere.

Figure 46. Omobrachyiulus trochiloides sp. nov., gonopods of ♂ paratypes from Baniskhevi Valley, Georgia (ZMUM) (A-D) and from near Nabeglavi, Georgia (NMNHS) (E) A left promere (flagellum broken off), caudal view B right opisthomere, mesal view C distal part of the same aspect D right opisthomere, lateral, somewhat caudal view E distal part of right opisthomere, lateral view. Scale bars: 0.2 mm (D), 0.1 mm (A, B, E), 0.05 mm (C). Abbreviations: ao apical outgrowth of basoposterior process, ap anterior process, bpp basoposterior process, dml distomesal lobe, f flagellum, fc flagellum channel, ml mesomeroidal lobe, mr median ridge, s solenomere.