Stygiiulus rotundatus ( Strasser, 1962 ) Vagalinski & Borissov & Bobeva & Canciani & Antić, 2022

Vagalinski, Boyan, Borissov, Simeon, Bobeva, Aneliya, Canciani, Giacomo & Antić, Dragan Ž., 2022, The mostly cavernicolous millipede genus Stygiiulus Verhoeff, 1929, stat. nov.: taxonomy, distribution and phylogenetic relationships (Diplopoda, Julida, Julidae), European Journal of Taxonomy 798, pp. 30-69 : 49-53

Stygiiulus rotundatus ( Strasser, 1962) comb. et stat. nov.

Figs 8–9 , 13

Typhloiulus (Stygiiulus) montellensis rotundatus Strasser, 1962: 57–58 , figs 68–69.

Typhloiulus montellensis rotundatus – Minelli 1985: 10. — Vagalinski et al. 2015: 343.

Diagnosis

A species of Stygiiulus stat. nov. with normal mouthparts. Differs from its most similar congener, S. montellensis comb. nov. by the distal part of mesomere being fronto-caudally compressed, ending with a rounded apex, vs the same being clavate, ending with a broad and flat apex in the latter species; and by the vulval operculum being relatively narrow, with an uneven, coarsed/undulating apical margin, vs the same being broader and with a smooth and gently concave apical margin in S. montellensis comb. nov.

Material examined

Lectotype (designated here) ITALY • ♂ 20-41-71 slide preparation; Veneto, province of Treviso , Refrontolo , Busa di Fave [ Bus de le Fave Cave ]; 7 May 1959; gonopods, flanges of pleurotergum 7; MHNG-ARTO-27001 .

Paralectotypes ITALY • 1 ♂ 28-43-74 slide preparation; same collection data as for lectotype; gonopods, antenna, legs 1, 2, 3, 7, mouthparts, flanges of pleurotergum 7; MHNG-ARTO-27002 • 1 ♂ 19.5-41-63 slide preparation; same collection data as for lectotype; gonopods, flanges of pleurotergum 7; MHNG-ARTO-27003 .

Other material

ITALY • 1 ♂; Veneto, province of Treviso, San Pietro di Feletto, Grotta [cave] di Foltran (1251 V / TV); 8 Aug. 1961; Paoletti leg.; specimen unbroken; MHNG • 1 ♂ 23-43-75 slide preparation; same collection data as for preceding; 8 Aug. 1971; gonopods, antenna, flanges of pleurotergum 7; MHNG- ARTO-27004 • 1 ♂ 17-38-61 slide preparation; same locality; date unknown; gonopods, antenna, flanges of pleurotergum 7; MHNG-ARTO-27005 • 1 ♂ 26-46-81 slide preparation; Veneto, province of Treviso, Farra di Soligo, Grotta [cave] di Collagù (1225 V /TV); 30 Oct. 1966; gonopods, antennae, gnathochilarium, legs 1 and 2 plus penis, flanges of pleurotergum 7; MHNG 901/5 • 2 ♂♂, 3 ♀♀; Veneto, province of Treviso, San Pietro di Feletto, La Bora Cave (1252 V /TV); 110 m a.s.l.; 9 Mar. 2008; D. Bianco and E. Piva leg.; H. Enghoff det. 2013; NHMD .

Comment

The original description of Strasser (1962) does not contain information on the number of type specimens and a holotype has not been designated. However, it can be inferred from text that the type locality is the cave Bus de le Fave near the village of Refrontolo, province of Treviso, and the material the description is based upon was collected on 7 th May and 10 th June 1959. The label data of three of the examined MHNG slides contain the same toponym and date. Since the position of the right gonopods in slide “ ♂ 20-41-71” is most similar to the aspect shown in Strasser’s (1962: fig. 68) description, we here designate that same slide as lectotype, in order to stabilize the nomenclature of the species under Article 74.1 of the ICZN.

Redescription

SIZE AND NUMBER OF BODY RINGS. ♂♂ with BRF 42–49+1+T, l = 17–28 mm, H = 1.3–1.4 mm; ♀ with BRF 50 +0+T, L = 27.5–33.5 mm, H = 1.54–1.92 mm.

COLOURATION ( Fig. 8 ). Mostly light grey, apparently further faded from the alcohol conservation, with a brownish transverse band at posterior parts of metazonae; head, telson and legs brown.

EXTERNAL STRUCTURES. 2 +2 supralabral setae (one ♀ with 5), spread in more or less equal distances from one another, and 12–16 labral setae. Antennae ( Fig. 8B ) 2–2.4 times as long as head and ca 1.5 as long as H in males, and ca 2 times and 1.3 times, respectively, in females; antennomere 5 2.5 times as long as broad; antennomeres 3–5 subequal in length, somewhat shorter than 2 and ca 1.3 times longer than 6.

MOUTHPARTS. Of normal julid type. Labrum tridentate. Lingual lamellae each with 2–3 basal, 1 median and 1 distal seta in a longitudinal row. Promentum markedly elongated, separating the lamellae in about their proximal ½. Gnathochilarial stipites each with a group of several short setae medially, just under lingual lamellae.

COLLUM. Completely smooth. Prozonae smooth. Metazonae with well-developed striation only ventrally, dorsally and laterally with short and shallow striae; length of setae from 9% (in mid-body and hind body rings) to 25% (in anterior-most rings) of H.

OZOPORES. Placed behind pro-metazonal suture at ca 2 ⁄ 5 (in more anterior rings) to almost ½ (in more posterior rings) of metazonal length measured from front to back. Tarsus of mid-body legs 1.9–2.2 times

as long as tibia and 2.7–3.6 times as long as apical claw. Mid-body legs 1–1.2 times as long as H in males, and ca 0.85 times in females.

TELSON ( Fig. 8E ). Epiproct stout, wedge-like, more or less straight, ending with a short and blunt hyaline tip directed completely distad or slightly dorsad, not reaching level of longest paraproctal setae. Hypoproct from narrowly rounded to blunt triangular, not protruding past rear contour of paraprocts in both sexes, bearing 5–10 submarginal and a pair of median parabasal setae. Paraprocts moderately to densely covered with long setae, without distinct rows of shorter setae along caudal margins.

MALE SEXUAL CHARACTERS. Leg-pair 1 (9A) rather compact, three-segmented hooks oriented towards one another, with relatively small, apically microdentate/micropapillate tibial outgrowths, without tarsal remnants. Leg-pairs 2 and 3 somewhat ticker than following legs. Tibial adhesive pads well developed until about mid-body, first several leg-pairs with a less strongly pronounced postfemoral pad in addition. Pleurotergum 7 ( Fig. 8C ) with considerably expanded ventral margins forming broad and rounded lobes. Penis ( Fig. 9B ) long, in situ visible behind coxae 2, basally broad, abruptly narrowing until ⅓ of its length, then running parallel-sided, before barely widening distally, ending with short, diverging apical lobes bearing small, pointed, terminal lamellae turned completely laterad.

GONOPODS ( Fig. 9C–D ). In situ completely concealed in gonopodal sinus and between lobes of pleurotergum 7.Mesomere slightly exceeding promere, both being considerably shorter than opisthomere. Promere (p in Fig. 9C ) slender oar-shaped, bent somewhat caudad, forming a narrowly rounded mesoapical corner; caudal face distally not too densely microsquamose/macropapillate, basally with a strongly pronounced, ridge-like internal lobe and a smaller, leaf-like external lobe. Mesomere ( Fig 9D, m in Fig. 9C ) narrow spade-like, with a flattened or broadly rounded apex directed distad; caudal face distally deeply concave and sparsely micropapillate. Opisthomere ( Fig. 9C ) relatively slender, with a strongly pronounced posterior hump (ph); velum (v) very broad, with a smooth frontal and a deeply serrated apical margin; solenomere with a rather stout, apically ciliate posterior branch (pb) and a very fine and pointed anterior branch (ab), shortly ciliate all along.

FEMALE SEXUAL CHARACTERS. Leg-pairs 1 and 2 somewhat thicker and slightly longer than following legs. Vulva ( Fig. 9E ) mostly symmetric: only mesal valve of bursa somewhat broader than lateral one; bursa slightly compressed on sides, with a relatively broad and shallow median cleft; each valve distally with one vertical row of several setae, side sclerites each with a pair of setae; operculum (op) somewhat narrowing distad, with an uneven, undulating apical margin exceeding bursa by ca ⅓ of total height of vulva, distally with a group of several setae each side. Receptaculum seminis consisting of two very short and narrow, somewhat folded tubes: a mesal (mt) and a lateral one (lt), both ending in two ovoid ampullae, the lateral one (la) being considerably larger than the mesal one (ma).

Distribution

Known from several caves in a small area on the southern side of the Venetian Prealps’ foothill, north of Treviso. All records come from the left side of the Piave River ( Fig. 13 , blue squares).

Figures

Fig. 8. Stygiiulus rotundatus (Strasser, 1962) comb. et stat. nov., ♀ (A) and ♂ (B–E) from La Bora Cave (NHMD). A. Habitus, lateral view. B. Anterior part of body, lateral, slightly ventral view.C. Pleurotergum 7, lateral view. D. Mid-body rings, lateral view. E. Telson, lateral view. Scale bars: A = 1 mm; B–E = 0.5 mm.

Fig. 9. Stygiiulus rotundatus (Strasser, 1962) comb. et stat. nov., paralectotype ♂ (A) (MHNG), ♂ from Grotta [cave] di Collagù (B) (MHNG) and ♂ (C–D) and ♀ (E) from La Bora Cave (NHMD). A. Leg-pair 1, oral view. B. Penis, oral/caudal view. C. Right gonopods, mesal view (inverted). D. Left mesomere, oral view. E. Left vulva, caudal, somewhat mesal view. Abbreviations: ab = anterior branch of solenomere; la = lateral ampulla; lt = lateral tube; m = mesomere; ma = median ampulla; mt = median tube; op = operculum; p = promere; pb = posterior branch of solenomere; ph = posterior hump; v = velum. Scale bars: A = 0.4 mm; B = 0.2 mm; C–E = 0.3 mm.

Fig. 13. General distribution of the species of the genus Stygiiulus stat. nov.