Stenostygnus huberi, Mamani & Porto & Iglesias & González, 2021

Mamani, Claudia Vanesa, Porto, Willians, Iglesias, Patricia P. & González, Abel Pérez-, 2021, Two new species of Stenostygnus from South America (Opiliones: Biantidae Stenostygninae), Zootaxa 4984 (1), pp. 182-202 : 193-196

Stenostygnus huberi spec. nov.

Figs 7–12

urn:lsid:zoobank.org:act:061A42CE-09C0-40FE-AF84-A14F1E773AC6

Type material. VENEZUELA, Lara: H olotype male (α) ( MIZA 0103461 ), Parque Nacional Yacambu , 15–16 Dec 2002, A. Pérez-González, A. Giupponi & Bernhard A. Huber, O. Villarreal M. & B. Striffler . Paratypes: 2 males (ss) (one male SEM voucher) , 6 females, 1 juvenile ( MNRJ 2429 ), with same data as for holotype . 1 male (ss) ( SEM voucher) (MACN-Ar 41020), with same data as for holotype . 1 male (ss), 1 female, 1 juvenile (MACN-Ar 41019), with same data as for holotype .

Etymology. Patronymic in honor of the Austrian arachnologist and friend Bernhard A. Huber in recognition of his remarkable contribution to arachnology, and also for being one of the collectors of the type series; name in the genitive case.

Diagnosis. Differs from all other species of Stenostygnus by the presence of granules in the interocular region ( Fig. 8 A ); patella IV of males with strong spiniform apophysis on the distal-retrolateral surface (Figs 10 A–B); ventral plate of the penis with a deep cleft basally fused and apically “V” shaped ( Fig. 11 ). It can be distinguished from Stenostygnus pusio by the lateral borders of the scutum almost parallel and mesotergal areas almost equally wide ( Fig. 8 A ) versus scutum lateral borders slightly arched (giving an oval appearance to the habitus) ( Pinto-da-Rocha 1995, fig. 1); presence on the pedipalp of a meso-medial spine on the femur and a meso-distal spine on the patella ( Fig. 9 D ) versus without spines in S. pusio ; pars distalis ventrally convex versus concave in S. pusio (Pinto-da- Rocha 1995, fig. 7). This species can be easily separated from S. martensi spec. nov. by the presence of scattered granules on the interocular area and mesotergal areas I to IV ( Fig. 8 A ) versus smooth areas in S. martensi spec. nov. ( Fig. 2 A ); presence of granules on the coxae III and IV ( Fig. 8 B ) versus smooth in S. martensi spec. nov. ( Fig. 2 B ); femur without ectal spines ( Fig. 9 E ) versus two small ectal spines in S. martensi spec. nov. ( Fig. 3 F ); lamina apicalis medially divided by a cleft that creates a “V” shape ( Fig. 11 A ) versus divided into two halves medially in contact in S. martensi spec. nov. ( Fig. 5 C ).

Description. Male (Holotype): measurements in Table 2 . Dorsum: Habitus slightly oval (almost rectangular) in shape ( Figs 7 A ; 8 A ). Carapace wider than long with the anterior border straight and unarmed. Cheliceral sockets not marked. Eyes widely separated; eye mounds very low, near sulcus I; interocular area with scattered granules, with greater concentration on the eye mounds ( Figs 7 C ; 8 A ). Carapace in lateral view slightly convex ( Figs 7 C ; 8 E ). Mesotergum in lateral view slightly convex ( Fig. 8 E ), divided into five well defined areas (i.e. with sulci well marked). Mesotergal areas I to IV with scattered granules. Lateral margins and posterior border of scutum with a row of small granules ( Fig. 8 A ). Ozopore with an oval and narrow orifice with a descending channel toward the posterior region ( Fig. 8 F ). Free tergites granulated ( Fig. 8 A, E ).

Venter: Without any conspicuous armature ( Fig. 8 B, C ). Spiracles visible ( Fig. 8 B, D ). Coxa I to III with minutes granules. Coxa II with tubercles in the medial region. Coxa IV smooth. ( Figs 7 B ; 8 B ).

Chelicerae: Without remarkable armature. Basichelicerite with a short bulla. Cheliceral hand with sparse setae ( Fig. 9 A ). Fingers thin, with uniform small teeth ( Fig. 9 B, C ).

Pedipalps: Raptorial and long, with spines concentrated on tibia and tarsus ( Fig. 9 D ). Coxa elongated, surpassing the anterior border of the carapace (i.e. can be seen in dorsal view) ( Fig. 7 A ) proximally with one small dorsoectal protuberance; trochanter small and smooth; femur thin and cylindrical, with a meso-medial spine ( Fig. 9 E ); patella clavate, swollen distally, with a meso-distal spine ( Fig. 9 D ); tibia with one ventro-basal spine and armed ventrally with three ectal and three mesal spines; tarsus mesal and ectally with three spines on each side ( Fig. 9 E ).

Legs: Thin, cylindrical, and elongated (Fig. 10 A). Coxa IV without remarkable armature; femur IV slightly curved; patella I–III short and swollen; patella IV with a prolateral-distal spiniform apophyses and dorsally roughly granulated (some of the granules looks like small pointed tip tubercles) (Fig. 10 B); tibia IV slightly swollen distally (Fig. 10 B); tarsi III and IV with dense scopula (Fig. 10 C, D). Tarsal formula: 6(3):11(3):6:6.

Color (specimen preserved in 80% ethanol): Body yellowish. Mesotergal areas, with slight brown reticulations ( Fig. 7 ).

Figure 10. Stenostygnus huberi spec. nov., male (ss) (paratype, MNRJ 2429), left leg IV (A retrolateral, B detail of patella and tibia, C detail of tarsus, D detail of scopula). Scale bars: A= 2 mm; B= 500 µm; C= 200 µm; D= 50 µm.

Genitalia: Penis with pars basalis and distalis well demarcated, pars distalis is markedly rounded contrasting with the thin and tubular pars basalis ( Fig. 11 A, D ). Pars distalis ending in a lamina apicalis medially divided by a cleft with a “V” shaped ( Fig. 11 C, F ). Lateral border of pars distalis armed with 6 pairs of leaf-like macrosetae and 2 subapical pairs of very short (truncated, not leaf-like) setae ( Fig. 11 B, F ). Dorsally the capsula externa has two wide and apically rounded titillators. The apical borders of the titillators are dorsally projected. The internal surface of titillators is covered by small digitiform projections ( Fig. 11 A, B ). Capsula interna with two laminar and sharply pointed conductors bearing an also laminar and pointed stylus with a ventral subapical opening of ductus ejaculatorius ( Fig. 11 G ). The cuticular area of the lateral macrosetae has a rugose (folding) appearance ( Fig. 11 B ), this could be an effect of thinner or less chitinous cuticular layer in this region, that could be (hypothetically) related to the region of pars distalis that became swollen during the turgescent stage in the hydraulic penial functioning, this inflation could be responsible for the macrosetae erection necessary for functional interaction with the ovipositor during copulation. These putative expansible areas could functionally correspond to the spongy body (‘Schwellkörper’ in Martens 1978) commonly observed in Asian biantids.

Male (ss) paratype (MNRJ 2429): measurements as in Table 2 . Similar to the male (α) in relation to the armature of the dorsal scutum ( Fig. 12 B, C ). Sexual dimorphism evident in patella IV as in the holotype but male (ss) with prolateral-distal spiniform apophyses and dorsal tubercles smaller in size ( Fig. 12 D ).

Female (paratype, MNRJ 2429): measurements as in Table 2 . Similar to male in relation to the armature of the dorsal scutum ( Fig. 12 A, C, E ), but without prolateral-distal spiniform apophyses and dorsal tubercles in patella IV ( Fig. 12 B ).

Variation. Measurements ( Table 2 ): Males (n=5): total body length (1.92–2.35), carapace length (0.71–0.75), mesotergal length (1.70–1.93), carapace maximum width (1.08–1.18), mesotergal scutum maximum width (1.42– 1.61), leg I (5.63–6.30), leg II (14.07–14.68), leg III (7.99–9.39), leg IV (11.61–13.77); Females (n=7): total body length (1.86–2.40), carapace length (0.64–0.73), mesotergal length (1.59–1.86), carapace maximum width (1.07– 1.10), mesotergal scutum maximum width (1.48–1.62), leg I (4.97–5.39), leg II (11.82–13.14), leg III (6.88–7.55), leg IV (9.37–10.44). Tarsal formula (n=12): 6–7(3):9–11(3):6:6.

Distribution. Known only from the type locality ( Fig.13 ).

Figures

FIGURES 2A–F. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692), habitus (A dorsal, B ventral, C detail of sternum, D detail of spiracle, E lateral, F detail of ozopore). Scale bars: A, B, E= 500µm; C= 200 µm; D= 50 µm; F= 100µm.

FIGURES 3A–F. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692). A–C Right chelicera (A ectal, B frontal, C detail of fingers). D–F Right pedipalp (D mesal, E detail of tibia and tarsus, F detail of femur). Scale bars: A, B, E= 200 µm; C, F= 100 µm; D= 500 µm.

FIGURES 5A–G. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692), penis (A, E dorsal, B, F lateral, C, G ventral, D detail of conductor and stylus). CO—conductor. LA—lamina apicalis. SO—stylus opening of ductus ejaculatorius. ST—stylus. Ti—Titillator. Scale bars:A= 50 µm; B, C, E-G= 100 µm; D= 20 µm. Stylus in green, conductors in pink and capsula externa in blue (For interpretation of the references to colour the reader is referred to the pdf version of this article).

FIGURES 7A–C. Stenostygnus huberi spec. nov., male (α) (holotype, MIZA 0103461), habitus (A dorsal, B ventral, C lateral). Scale bars: A, B= 1 mm, C= 500 µm.

FIGURES 8A–F. Stenostygnus huberi spec. nov., male (ss) (paratype, MNRJ 2429), habitus (A dorsal, B ventral, C detail of sternum, D detail of spiracle, E lateral, F detail of ozopore). Scale bars: A = 1 mm; B, E= 500 µm; C, F= 100 µm; D= 20 µm.

FIGURES 9A–E. Stenostygnus huberi spec. nov., male (ss) (paratype, MNRJ 2429). A–C Left chelicera (A ectal, B frontal, C detail of fingers), D–E Left pedipalp (D ectal, E detail of femur). Scale bars: A–C= 200 µm; D= 1 mm; E= 500 µm.

FIGURES 11A–G. Stenostygnus huberi spec. nov., penis (A–B male (ss) paratype, MNRJ 2429; C male (ss), paratype, MACN 41020; D–G holotype male (α), MIZA 0103461). A, D Dorsal view. B, E, G Lateral view (G with detail of stylus and conduc- tors). C, F Ventral view. LA—lamina apicalis. Ti—Titillator. Scale bars: 100 µm. Stylus in green, conductors in pink and capsula externa in blue (For interpretation of the references to colour the reader is referred to the pdf version of this article).

FIGURES 12A–F. Stenostygnus huberi spec. nov., sexual dimorphism (A–B female paratype, MNRJ 2429; C–D male (ss) paratype, MACN 41020; E–F (holotype male (α), MIZA 0103461), A, C, E Dorsal view. B, D, F Detail of patella. Scale bars: A, C, E= 2 mm; B, F= 200 µm; D= 500 µm

FIGURE 13. Geographical distribution of the genus Stenostygnus in South America. Stenostygnus pusio (circles) in Colombia, Ecuador and Brazil, Stenostygnus huberi spec. nov. (square) in Lara State, Venezuela and Stenostygnus martensi spec. nov. (triangle) in Mérida State, Venezuela.