Micropachyiulus filiformis, Vagalinski & Evsyukov & Chumachenko & Zabiyaka, 2023

Vagalinski, Boyan, Evsyukov, Aleksandr P., Chumachenko, Yuri A. & Zabiyaka, Igor Y., 2023, A review of the genus Micropachyiulus Verhoeff, 1899 and description of the related Armeniopachyiulus gen. nov. (Diplopoda: Julida: Julidae: Pachyiulini), Zootaxa 5239 (2), pp. 221-246 : 235-239

Micropachyiulus filiformis sp. nov.

Figs 1B, C , 8–10

Material examined. Holotype: ♂ (in 2 pieces, gonopods in microtube) ( NMNHS), Romania, Oltenia, Râmnicu Vâlcea, Căpătânii Mts, Mt Stogu , 45.2754°N, 24.1330°E, 1080 m a.s.l., Corylus , Fagus , Acer pseudoplatanus , Fraxinus , Abies , Parietaria etc., in thick leaf litter, 01.XI.2021, H. Reip, K. Voigtländer, D. Antić, D. Stojanović, and B. Vagalinski leg.

Paratypes: 1 ♂ (in 4 pieces, head plus collum, leg-pair 1 and gonopods prepared for SEM, leg pair 2, right leg 3, and right flange of pleurotergum 7 in microtube), 4 (supposedly) adult ♀♀ (one in two pieces with left vulva in microtube, the others unbroken), 1 subadult female (in head plus collum and rest of body) ( NMNHS), same collecting data as for holotype ; 1 ♂ (unbroken), 2 ♀♀ (unbroken) ( NHMW MY 10326 ), same data as for holotype .

Diagnosis. A species of Micropachyiulus with ommatidia. Most similar to Micropachyiulus caucasicus sp. nov., both being characterized by a very long and thin solenomere of the opisthomere, without apical bulge or projection, a minute, spike-like outgrowth of the mesomeral process, and an opisthomeral posterior lamella expanding in a mesal ridge partly concealing the distal section of the sperm channel.

Differs from M. caucasicus sp. nov. by a flat vs. bulging anterior surface of the opisthomere, by the posterior lamella being overgrown with seti-/spiniform filaments, vs. same being smooth, by the promere being abruptly constricted in the middle, vs. same gradually narrowing towards apex, by the shorter and more finely serrated distal ridge of the latter, as well as by the shape of male leg-pair 1: tarsal remnants present as micropapillate bulges, vs. the latter absent, and with broad and flattened vs. slender tibial outgrowths.

Also resembles M. paucioculatus by the very long solenomere of the opisthomere, but differs clearly from it by the solenomere lacking an apical bulge or projection and by the minute, spike-like (vs. well-developed, slender) outgrowth of the mesomeral process.

Etymology. Meaning ‘thread-like’ in Latin, after the long and very fine solenomere, characteristic of this new species. Adjective.

Description. Measurements: holotype with BRF 44 + 2 + T, L = 8.6 mm, H = 0.5 mm; paratype ♂♂ with BRF 38 + 3 + T, L = 6.7 mm, H = 0.45 mm, and BRF 46 + 1 + T, H = 0.53 mm, L impossible to be accurately measured due to the strongly coiled body; paratype ♀♀ with BRF 36–48 + 1–3 + T, L = 8.3–10.6 mm, H = 0.58–0.65 mm.

Colouration: Beige to brown in ethanol; living specimens ( Fig. 1B, C ) whitish to very light grey-beige; the gut partly visible by transparency, the orange to light red repugnatorial glands clearly visible under the cuticle.

Head ( Fig. 8A ): With 2–5 pigmented ommatidia arranged in one or two rows on each side. Vertigial, supralabral and labral setae: 2, 4 and 13–16, respectively. Antennae ( Fig. 8B ) ca 1.35 times as long as head in males and ca 1.25 times in females; antennomere 5 ≥ 2> 4 ≥ 3> 6; 5 ca 1.6 times as long as broad and 1.8–9 times as broad as 2; sensilla basiconica of similar conformation as in M. paucioculatus , but with a denser whorl of better developed sensilla on antenomere 7. Mandibular stipites in males not expanded. Labrum tridentate. Gnathochilarium with 3 (usually) or 4 (in some specimens) distal setae and with a very short medial seta on each stipes; stipital palps as in M. paucioculatus ; promentum as in M. paucioculatus , but setae on lingual lamella clearly grouped in 2 proximal and 1 distal seta rather than nearly equally spaced.

Trunk and legs: Walking legs ( Fig. 10A, B ) relatively short: ML 0.65–0.7 times as long as H in males and 0.45–0.55 times in females. Tarsus of ML ca 1.3–1.45 times as long as tibia and ca 2–2.5 times as long as apical claw. Accessory claws absent from all legs in both sexes.

Telson: Pre-anal ring evenly and rather densely setose. Epiproct long (usually somewhat exceeding, rarely reaching level of tip of longest paraproctal setae), gradually bent ventrad, ending with a pointed hyaline tip. Other trunk and leg characters as in M. paucioculatus .

Male sexual characters: Leg-pair 1 ( Fig. 8C, D ) 3-segmented hooks oriented mostly mesad and slightly anteriad; tibial outgrowth rounded, dorso-ventrally flattened, tarsal remnant present as a massive, micropapillate bulge; the distal podomere with a verrucose hump (h) basally on mesal side. Legs 2 ( Fig. 10A ) slightly thicker and ca as thick as following legs. Ventral adhesive pads altogether absent. Flanges of pleurotergum 7 ( Fig. 10C ) ventrally forming rather narrow, rounded lobes originating at the border zone between pro- and metazona, directed ventro-mesad.

Gonopods ( Figs 9 , 10D ) in situ mostly concealed in gonopodal sinus. Promere ( Fig. 9B, C and P in Figs 9A , 10D ) slender, somewhat overreaching opisthomere, similar in shape to that in M. paucioculatus , but more spoonshaped, i.e. lateral margin sharply incised in the middle, then going gradually convex until the narrowly rounded apex; mesal (mr) and lateral (lr) ridges short and rather weakly pronounced, distal ridge (dr) well-pronounced, marginally finely serrated; a rather shallow median groove (mg) between mesal and lateral ridges. Opisthomere ( Fig. 9D–F and O in Figs 9A , 10D ) relatively slender, but somewhat stouter than in M. paucioculatus , more or less straight rather than sigmoid in lateral or mesal view; mesomeral process (m) completely vestigial, present as a weakly pronounced lamella, distally forming a minute, pointed outgrowth (mp) directed anteriad; posterior lamella (l) well-developed, expanding in a mesal crest concealing apical section of sperm channel (sc); its mesal side and the area between the lamella and the sperm channel with numerous setiform filaments (sf), these being much shorter than in M. paucioculatus ; solenomere (s) very long and fine, thread-like, more or less bent or coiled anteriad.

Female sexual characters: Leg-pairs 1 considerably, 2 slightly, ticker than following legs. Vulva ( Fig. 10E ) stout, slightly compressed on sides; median cleft positioned sub-apically, surrounded by a narrow oval median field (mf); operculum (op) slightly higher than bursa, apically concave, ending up with a blunt hyaline protrusion on each side; two smaller and tapering protrusions present apically on bursa; each bursal valve bearing three vertically arranged setae, operculum non-setose. RS composed of a very thin and not too long central tube (ct) leading to a distinct, nearly spherical, central ampulla (ca), and a somewhat thicker and more strongly curved posterior tube (pt) ending in an ovoid posterior ampulla (pa).

Distribution ( Fig. 14 , red circle). Romania: South Carpathians: Căpătânii Mts: Mt Stogu (type locality).

Figures

FIGURE 1. Micropachyiulus spp., habitus. A. Micropachyiulus paucioculatus (Verhoeff, 1899), living female from Cloşani, Romania. B. and C. Micropachyiulus filiformis sp. nov., living ♂ (NMNHS) and ♀ paratypes, respectively. D. and E. Micropachyiulus caucasicus sp. nov., ♂ and ♀ paratypes (ZMUM), respectively. Scale bars: 0.5 mm. A–C taken not to scale. Photo credit: A. H. Reip, B. and C. D. Antić.

FIGURE 8. Micropachyiulus filiformis sp. nov., ♂ paratype (NMNHS). A. Head, ventral view. B. Distal part of right antenna, ventral view. C. Leg-pair 1, anterior view. D. Left leg 1, anterior view. Abbreviations: h: verrucose hump. Scale bars: 0.2 mm (A), 0.1 mm (B, C), 0.05 mm (D).

FIGURE 9. Micropachyiulus filiformis sp. nov., ♂ paratype (NMNHS). A. Left gonopods, mesal view (mesomeral process partly ruptured). B. Right promere, posterior view. C. Distal part of the same. D. Right opisthomere, postero-lateral view (tip of solenomere broken off). E. Distal part of the same. F. Distal part of left opisthomere, mesal view (mesomeral process partly ruptured). Abbreviations: dr: distal ridge, l: posterior lamella, lr: lateral ridge, m: mesomeral process, mg: median groove, mp: apical outgrowth of mesomeral process, mr: mesal ridge, O: opisthomere, P: promere, s: solenomere, sc: sperm channel, sf: setiform filaments. Scale bars: 0.1 mm (A, D), 0.05 mm (B, C, E, F).

FIGURE 10. Micropachyiulus filiformis sp. nov., ♂ (A–D) and ♀ (E) paratypes (NMNHS). A. Left leg 2, anterior view. B. Left leg 3, anterior view. C. Right flange of pleurotergum 7, ventro-lateral view. D. Right gonopods, mesal view. E. Left vulva, mesoposterior view. Abbreviations: ca: central ampulla, ct: central tube, dr: distal ridge, l: posterior lamella, m: mesomeral process, mf: median field, mp: apical outgrowth of mesomeral process, mr: mesal ridge, O: opisthomere, op: operculum, P: promere, pa: posterior ampulla, pt: posterior tube, s: solenomere, sf: setiform filaments. Scale bars: 0.1 mm.

FIGURE 14. Distribution of the genera Micropachyiulus Verhoeff, 1899 and Armeniopachyiulus gen. nov.