Stygiiulus fimbriatus (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 : 35-41

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

Figs 1–3 , 13

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

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

Diagnosis

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

Material examined

Holotype ITALY • ♂; slide preparation plus ethanol sample; Friuli-Venezia Giulia, San Pietro al Natisone , Grotta [cave] di San Giovanni d’Antro ; slide no. 1003: gonopods, antennae, leg-pairs 1, 2, 3, 7, penis, gnathochilarium, flanges of pleurotergum 7; ethanol sample: broken in six pieces; MHNG-ARTO-26720 .

Other material

ITALY • 3 ♂♂, 1 ♀; Friuli-Venezia Giulia, Prestento di Torreano, Foran di Landri Cave (11 / 46FR); 10 Jul. 2019; G. Canciani and M. Colautti leg.; IBER • 4 ♂♂, 2 ♀♀; same collection data as for preceding; IZB • 1 ♂; same collection data as for preceding; NHMD .

Comment

Since the original description was based upon one male which was not designated by Strasser (1971a) as holotype, we here consider that male as a holotype fixed by monotypy, in order to stabilize the nomenclature of the species under Article 73.1.2 of the ICZN.

Redescription

SIZE AND NUMBER OF BODY RINGS. Non-type ♂♂ with BRF 26–31 +0–1 +T, L = 14–20 mm, H = 1.1– 1.25 mm; non-type ♀♀ with BRF 28–32 +0–1 +T, L = 16–21 mm, H = 1.3–1.6 mm.

COLOURATION ( Fig. 1A–B, E–G ). Generally brown-beige; metazonae with a narrow transverse dark brown band before their last third, the band gradually narrowing ventrally.

EXTERNAL STRUCTURES. Head with 2 vertigial, 2+2 supralabral and 16–18 labral setae. Antennae ( Fig. 1B ) 2.3 times as long as head and 2.3–2.4 times as long as H in males, and 2 times and 1.85–1.9 times, respectively, in females; antennomere 5 3.12–3.15 times as long as broad; antennomeres 2–5 subequal in length, 1.3–1.6 times as long as 6. 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 ( Figs 1C–D, H , 2A–B ). With moderate hydrophilous modifications (sensu Enghoff 1985): Labrum either edentate ( Fig. 1D ) or with three well-developed labral teeth ( Fig. 1C ). Gnathochilarium ( Fig. 2A ) rather short and distally markedly broad, with the 3 long distal setae on each stipes usual for the family, stipites medially each with 4–10 short setae arranged longitudinally, stipital palps conspicuously large; promentum large (pm), completely separating lingual lamellae, the latter each with 2–3 proximal and 1 distal seta. Gnathal lobes of mandibles ( Fig. 2B ) with the external (et) and the internal tooth (it) slightly to moderately reduced; molar plate (mp) relatively small (but larger compared to that in S. ausugi comb. nov.); the four pectinate lamellae (pl) consisting of slender and very densely set teeth. Hypopharynx distally densely ciliate, posterior node reduced, with roundish posterior margin ( Fig. 1H ).

COLLUM. Entirely smooth, its frontolateral margin bent outwards. Body rings considerably vaulted. Prozonae smooth. Metazonae with well-developed striation only ventrally, dorsally and laterally with faint and short striae only in anterior parts; setae ca 20% of H ( Fig. 1F ), arranged in moderately dense whorl. Ozopores very small, placed behind pro-metazonal suture at ca 2 ⁄ 5 of metazonal length measured from front to back. Tarsus of mid-body legs 2.2–2.4 times as long as tibia and 2.8–3.7 times as long as apical claw; accessory claw absent. Mid-body legs 1.5–1.6 times as long as H in males, 1.4 times in females.

TELSON ( Fig. 1G ). Epiproct short and stout, straight all along, ending with a short hyaline tip turned more or less dorsad, barely protruding behind caudal contour of paraprocts. Hypoproct broadly rounded, tightly fitting under paraprocts, with rather evenly setose ventral face. Paraprocts densely covered with long setae, without distinct rows of shorter setae along caudal margins.

MALE SEXUAL CHARACTERS. Leg-pair 1 ( Fig. 3A ) rather slender hooks oriented towards one another; with three complete and another one or two faintly indicated segments; with apically densely microdentate tibial outgrowths, and without or with barely visible tarsal remnants. Legs of more anterior body rings with an adhesive pad on tibia, most pronounced in leg-pair 2, gradually diminishing in caudal direction, completely disappearing around mid-body; tibia and femora without modifications. Pleurotergum 7 ( Fig. 1E ) caudo-ventrally forming small rounded lobes directed caudad. Penis ( Fig. 3B ) long, in situ visible behind coxae 2, slender hourglass shaped: broadest at base, narrowing until the middle, then slightly widening again, ending with short, diverging, apical lobes bearing fine, blunt, terminal lamellae.

GONOPODS ( Figs 1B , 2C–E , 3C ). In situ obliquely protruding from gonopodal sinus with their distal parts ( Fig. 1B ). Promere ( Fig. 2C, p in Fig. 3C ) somewhat higher than mesomere, both being significantly surpassed by the opisthomere. Promere stout, oar-shaped (broadest apically), forming a near rightangled meso-apical corner and a broadly rounded latero-apical corner; apical margin bent somewhat frontad; caudal face distally densely microsquamose, basally with an internal and an external lobe, both being short and robust, partly fused to one another. Mesomere ( Fig. 2D, m in Fig. 3C ) narrow spoon-like, with the apex turned meso-frontad; caudal face distally deeply concave and sparsely microsquamose. Opisthomere ( Figs 2E , 3C ) markedly slender, with a distinct, obtuse posterior hump (ph); velum (v) pointing distad, both its frontal and caudal margin apically deeply serrated; solenomere with a slender posterior branch (pb) bent caudad, ending with several long ciliae, anterior branch (ab) vestigial, barely protruding, mostly concealed between the velum and the posterior solenomeral branch, densely ciliate; with 2 or 3 fine distal setiform filaments (sf), and sometimes with a variously developed basal spine (bs) at flagellum channel (fc).

FEMALE SEXUAL CHARACTERS. Leg-pairs 1 and 2 visibly shorter, 1 also thicker, than following legs. Ventral margin of body ring 3 with roundish anterior lobe ( Fig. 1I ). Vulva ( Fig. 3D ) somewhat compressed in the sagittal plane, mostly symmetric: lateral side of operculum higher and apically more pointed than mesal one; each valve of bursa with one vertical row of setae; operculum (op) broad and thick, with a concave apical margin, exceeding bursa by ca ¼ of total height of vulva, medio-laterally with two longitudinal rows of setae each side. Receptaculum seminis consisting of two short and narrow, somewhat folded tubes – a lateral (lt) and a mesal one (mt), both insignificantly widening towards bottom, not forming distinct ampullae.

Distribution

Known only from two caves in the Julian Alps in Italy, near the border with Slovenia ( Fig. 13 , yellow circles).

Remark

The new locality of S. fimbriatus comb. et stat. nov., Cave Foran di Landri, is an active cave with a stream running through it year-round, flowing out of the entrance, after passing through a series of syphons

(four discovered so far). All examined specimens were found right beyond the first two syphons, ca 40 meters from the entrance. This part of the cave includes a number of ponds, and it probably becomes completely flooded during rainy periods ( Canciani 2019). Part of the individuals was observed moving on the surface of the ponds – a behaviour most likely associated with a filtrating rather than chewing feeding mode, in which small organic particles adhere to the fine and densely set teeth of the pectinate lamellae and to the cilia of the hypopharynx.

The cave of San Giovanni d'Antro (the type locality) is of the same type as Foran di Landri, and Strasser (1971a) noted that it was occasionally flooded.

Figures

Fig. 1. Stygiiulus fimbriatus (Strasser, 1971) comb. et stat. nov., ♂♂ (A–H) and ♀ (I) from Foran di Landri Cave (IZB). A. Habitus, lateral view. B. Anterior part of body, lateral view. C. Labrum, frontodorsal 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, fronto-ventral 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. 2. Stygiiulus fimbriatus (Strasser, 1971) comb. et stat. nov., ♂ from from Foran di Landri Cave (IBER). A. Gnathochilarium, ventral view. B. Gnathal lobe of left mandible, ventral view. C. Left promere, caudal view. D. Left mesomere, oral view. E. Distal part of left opisthomere, mesal view. Abbreviations: ab = anterior branch of solenomere; el = external lobe; et = external tooth; il = internal lobe; it = internal tooth; mp = mollar plate; pb = posterior branch of solenomere; ph = posterior hump; pl = pectinate lamellae; pm = promentum; sf = setiform filaments; v = velum. Scale bars: A = 0.2 mm; B = 0.1 mm; C–D = 0.05 mm; E = 0.02 mm.

Fig. 3. Stygiiulus fimbriatus (Strasser, 1971) comb. et stat. nov., holotype ♂ (A, B) (MHNG), ♂ (C) (IZB) and ♀ (D) (IBER) from Foran di Landri Cave. A. Leg-pair 1, caudal view. B. Penis, oral/caudal view. C. Left gonopods, mesal view. D. Left vulva, caudal, somewhat mesal view. Abbreviations: ab = anterior branch of solenomere; bs = basal spine; fc = flagellum channel; lt = lateral tube; m = mesomere; mt = median tube; op = operculum; p = promere; pb = posterior branch of solenomere; ph = posterior hump; v = velum. Scale bars = 0.2 mm.

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