Stygiiulus gentianae (Strasser, 1971) 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 : 41-45

Stygiiulus gentianae (Strasser, 1971) comb. et stat. nov.

Figs 4–6 , 13

Typhloiulus ausugi gentianae Strasser, 1971a: 13–14 , fig. 15.

Typhloiulus ausugi gentianae – Minelli 1985: 10. — Vagalinski et al. 2015: 336–337.

Material examined

Lectotype (designated here) ITALY • ♂; Veneto, Bosco del Cansiglio [Cansiglio Forest], Bus [cave] de la Genziana ; specimen unbroken; MHNG-ARTO-26721 .

Paralectotypes ITALY • 1 ♀; same collection data as for lectotype; specimen unbroken; MHNG-ARTO-26722 • 1 ♂ slide preparation; same collection data as for lectotype; labrum, mandibles, gnathochilarium, antennae, penis, flanges of pleurotergum 7; MHNG-ARTO-26723 • 1 ♂ slide preparation; same collection data as for lectotype; gonopods; MHNG-ARTO-26724 .

Other material

ITALY • 1topotype♀; Veneto, province of Treviso, Bosco del Cansiglio [Cansiglio Forest], Fregona ,q. 1020, Bus [cave] de la Genziana (1000 V /TV); 3 Oct. 1985; E. Piva leg. and ded.; NHMD • 1 topotype ♂, 2 topotype ♀♀; same locality as for preceding; 22. Oct. 1994; E. Piva leg.; H. Enghoff det. 2013; NHMD • 2 ♂♂, 1 ♀; Friuli-Venezia Giulia, Cansiglio Cavallo, Barcis (PN), Grotta [cave] della Vecchia Diga (786 / 327FR); 484 m a.s.l.; 30 Jun. 1996; G. Peretto and E. Piva leg.; H. Enghoff det. 2013; NHMD • 2 ♂♂, 1 ♀; Friuli-Venezia Giulia, province of Pordenone, Montereale Valcellina (PN), Inghiottitoio [karstic pot-hole] della Val di Pai (1027 / 469FR); 30 Aug. 1984; Comotti leg.; R. Pisoni ded. 1989; NHMD .

Comment

Since the original description was based upon three males and two females, none of which was designated by Strasser (1971a) as holotype, we here designate the only intact male specimen as lectotype, in order to stabilize the nomenclature of the species under Article 74.1 of the ICZN.

Diagnosis

A species of Stygiiulus stat. nov. with modified mouthparts. Differs from its most similar congener, S. fimbriatus comb. et stat. nov., by gonopod details, viz. promere and opisthomere being turned towards one another rather than apically both bent frontad, velum with a smooth rather than entirely serrated anterior margin; by the weakly rather than strongly pronounced posterior part of pleurotergal flange 7 in males; by the vulval operculum being convex rather than concave, exceeding bursa by ca 2 ⁄ 5 rather than with ¼ of total height of vulva; by the entirely subtriangular ventral margin of body ring 3 in females, rather than ventral margin with a small, roundish anterior lobe; and by the somewhat shorter epiproct.

Redescription

SIZE AND NUMBER OF BODY RINGS. Lectotype ♂ with BRF 36 + 0+T, L = 18 mm, H = 1.3 mm, paralectotype ♀ with BRF 33 +0+T, L = 16.5 mm, H = 1.2 mm; topotype ♂ with BRF 31 +0 +T, L = 20.5 mm, H = 1.4 mm; topotype ♀♀ with BRF 31–35 +0–1 +T, L = 19–22 mm, H = 1.4–1.7 mm; males from Val di Pai with BRF 30–32 +1 +T, L = 13 mm, H = 1.05–1.1 mm; female from Val di Pai with BRF 30 +1 +T, L = 17 mm, H = 1.3 mm; males from Vecchia Diga with BRF 29–31 +0+T, L = 18–19 mm, H = 1.15– 1.2 mm, female from Vecchia Diga with BRF 27 +1+T, L = 18.5 mm, h = 1.3 mm. In general, males with BRF 29–36+ 0–1+T, L = 13–20.5 mm, H = 1.05–1.3 mm; females with BRF 27–36 +0–1+T, L = 16.5–22 mm, H = 1.2–1.7 mm.

COLOURATION ( Fig. 4A–B, F–G ). Completely pallid, probably as a result of the long alcohol conservation (considering the presence of some colour pattern in the highly similar S. fimbriatus comb. et stat. nov.).

EXTERNAL STRUCTURES. Head with 2 vertigial, 2+2 supralabral and 16–23 labral setae.Antennae ( Fig. 4B ) 2.5 times as long as head and 2.4–2.5 times as long as H in males, and 2.1–2.2 times and 1.8–2.1 times, respectively, in females; antennomere 5 2.8 times as long as broad. Antennomeres V and VI each with a terminal corolla of large sensilla basiconica bacilliformia; antennomere VII with a terminal corolla of small sensilla basiconica bacilliformia.

MOUTHPARTS ( Fig. 4C–D, H ). Generally similar to those of S. fimbriatus comb. et stat. nov., including individuals with edentate labrum ( Fig. 4D ), as well as individuals with three small but distinct labral teeth ( Fig. 4C ). Gnathochilarial stipites each with a row of 2–5 rather than up to 10 setae. Posterior node of hypopharynx ( Fig. 4C ) reduced, with somewhat squarish posterior part.

COLLUM. Collum as in S. fimbriatus comb. et stat. nov., but with the frontolateral margin only slightly bent outwards. Metazonal striation faint and sparse even on ventral side; setation somewhat shorter than in fimbriatus – around 10% of H. Tarsus of mid-body legs 2.1–2.3 times as long as tibia.

TELSON ( Fig. 4G ). Epiproct very short, not protruding behind caudal contour of paraprocts), ending with a minute hyaline tip turned more or less dorsad. Hypoproct more narrowly rounded compared to the former species, blunt subtriangular in some specimens (regardless of sex).

All remaining external somatic characters as in S. fimbriatus comb. et stat. nov.

MALE SEXUAL CHARACTERS. Male leg-pair 1 ( Fig. 5A ) similar to the condition in S. fimbriatus comb. et stat. nov., differing in having a proportionately smaller tibial part, apically more sparsely microdentate/ microtuberculate. Male walking legs with more pronounced tibial pads than in S. fimbriatus comb. et stat. nov., these being still visible behind mid-body. Penis ( Fig. 5B ) as in the former species, but with longer and more tapering terminal lamellae.

GONOPODS ( Figs 5C , 6 ). Very similar to those of S. fimbriatus comb. et stat. nov., differing from the latter species mainly by the pro- (p) and mesomere (m) being gradually bent towards one another, rather than both apically turned frontad, and by the smooth rather than ciliate anterior margin of velum (v); also promere in S. gentianae comb. et stat. nov. relatively broader, with the external lobe (el) significantly higher than, rather than subequal to, the internal one (il); posterior branch of solenomere (pb) somewhat more robust, anterior branch of solenomere (ab) and posterior hump of opisthomere (ph) of same size and shape as in S. fimbriatus comb. et stat. nov.

FEMALE SEXUAL CHARACTERS. Leg-pairs 1 and 2 shorter, 1 also slightly thicker, than following legs. Ventral margin of body ring 3 subtriangular ( Fig. 4I ). Vulva ( Fig. 5D ) mostly symmetric, somewhat compressed in the sagittal plane; operculum (op) very large, with a convex apical margin forming several rounded bumps, exceeding bursa by nearly 2 ⁄ 5 of total height of vulva; setation on both bursa and operculum in a similar pattern as in S. fimbriatus comb. et stat. nov., but with 1–2 setae on side sclerites in addition. Receptaculum seminis represented by two short and narrow tubes: a mesal one (mt) leading to an ovoid ampulla (ma), and a lateral one (lt) ending without distinct ampulla at bottom.

Distribution

Known from several caves in the easternmost part of the Venetian Prealps mountain range ( Fig. 13 , red circles).

Remark

Strasser (1971a) wrote that this species was found on wet vertical walls (common place for many troglobitic arthropods with mouthpart modifications).

Figures

Fig. 4. Stygiiulus gentianae (Strasser, 1971) comb. et stat. nov., ♂ (A–C, E, G) from Grotta [cave] della Vecchia Diga, ♂ topotype (D, H) and ♀ topotype (F, I) (NHMD). A. Habitus, lateral view. B. Anterior part of body, lateral view. C. Labrum, frontal view. D. Labrum, dorsal view. E. Pleurotergum 7, lateral view. F. Mid-body rings, lateral view. G. Telson, lateral view. H. Posterior node of hypopharynx, frontoventral view. I. Lobe of body ring 3, lateral view. Scale bars: A = 1 mm; B–G, I = 0.5 mm; H = 0.1 mm.

Fig. 5. Stygiiulus gentianae (Strasser, 1971) comb. et stat. nov., ♂ paralectotype (A–B) (MHNG), topotype ♂ (C) (NHMD) and topotype ♀ (D) (NHMD). A. Leg-pair 1, oral view. B. Penis, oral/caudal view. C. Left gonopods, mesal view. D. Left vulva, caudal, somewhat mesal view. Abbreviations: ab = anterior branch of solenomere; 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, C–D = 0.2 mm; B = 0.1 mm.

Fig. 6. Stygiiulus gentianae (Strasser, 1971) comb. et stat. nov., ♂ from Grotta [cave] della Vecchia Diga (NHMD). A. Right promere, caudal view. B. Right mesomere, oral view.C. Distal part of left opisthomere, mesal view. Abbreviations: ab = anterior branch of solenomere; el = external lobe; il = internal lobe; pb = posterior branch of solenomere; ph = posterior hump; v = velum. Scale bars = 0.05 mm.

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