Stenostygnus martensi, 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 : 185-188

Stenostygnus martensi spec. nov.

Figs 1–6

urn:lsid:zoobank.org:act:F4E10B5C-238F-4573-A1BC-93C657A2DF30

Type material. VENEZUELA, Mérida: Holotype male ( MIZA 0103460 ): Andres Bello , vía a La Azulita, El Chorotal, Sector El Frontino, 8.663598°; -71.419705°, 3 Feb 2017, 2200 m a.s.l., Osvaldo Villareal, Néstor Sánchez, Andrés García . Paratypes: 1 male ( SEM voucher), 3 females ( MNRJ 2692 ), with same data as for holotype . 2 females (MACN-Ar 41022), with same data as for holotype .

Etymology. Patronymic in honor to the German zoologist Jochen Martens, in recognition of his enormous contribution to widen our knowledge of harvestmen. His work helped to found the basis of the new opilionology—as opposed to the old typological approach—and still exerts great influence on new generations of opilionologists; name in the genitive case.

Diagnosis. Differs from all the species of Stenostygnus by the following characteristics: absence of granules on mesotergal areas, posterior border of the scutum ( Fig. 2 A ) and ventral surface of the coxae III and IV ( Fig. 2 B ); males with a retrolateral row of pointed strong tubercles on tibia IV ( Figs 4 A, B ; 6 D ); lamina apicalis medially divided with both halves medially in contact ( Figs 5 A, C, E, G ). It can be distinguished from Stenostygnus pusio by the lateral borders of the scutum almost parallel, and mesotergal areas almost equally wide ( Fig. 2 A ) versus scutum lateral borders slightly arched (giving an oval appearance to the habitus) ( Pinto-da-Rocha 1995, fig. 1); presence of ventral armature on the femur of the pedipalp versus unarmed in S. pusio ; pars distalis ventrally convex versus concave in S. pusio ( Pinto-da-Rocha 1995, fig. 7). It differs from S. huberi spec. nov. by the smooth interocular area and mesotergal areas I to IV smooth ( Fig. 2 A ) versus presence of scattered granules in S. huberi spec. nov. ( Fig. 8 A ); absence of granules on III and IV coxae ( Fig. 2 B ) versus presence of granules on III and IV coxae in S. huberi spec. nov. ( Fig. 8 B ); femur with two small ectal spines ( Fig. 3 F ) versus without ectal spines in S. huberi spec. nov. ( Fig. 9 E ); lamina apicalis divided in two halves medially in contact ( Fig. 5 C ) versus medially divided by a cleft that creates a “V” shape in S. huberi spec. nov. ( Fig. 11 A ).

Description. Male (holotype): Measurements in Table 1 . Dorsum: Habitus oval ( Figs 1 A ; 2 A ). Carapace wider than long with the anterior border straight and smooth. Cheliceral sockets not marked. Eyes separated; eye mounds high and smooth, near sulcus I; interocular area completely smooth ( Fig. 2 A ). Carapace in lateral view slightly convex ( Figs 1 C ; 2 E ). Mesotergum in lateral view convex with areas well defined, with sulcus well marked ( Fig. 2 E ). Mesotergal areas I to IV unarmed. Lateral margins of scutum dorsally with a row of small granules ( Figs 2 E–F ). Ozopore with an oval orifice with a descending channel toward the posterior region ( Fig. 2 F ). Free tergites with few granules ( Fig. 2 A ).

Venter: Without any remarkable features ( Figs 2 B–C ). Spiracles visible ( Figs 2 B, D ). Coxae I and II with minute granules. Coxae III and IV smooth. ( Fig. 2 B )

Chelicerae: Without remarkable armature. Basichelicerite smooth with a short bulla. Cheliceral hand unarmed, covered with sparse setae ( Figs 3 A–B ). Fingers thin, each with four teeth spaced one from the other ( Figs 3 B–C ).

Pedipalps: Raptorial, with spines concentrated on tibia and tarsus ( Fig. 3 D ). Coxa elongated, surpassing the anterior border of the carapace (i.e. can be seen in dorsal view) ( Figs 1 A ; 2 A ), proximally with one small dorsoectal protuberance; trochanter small and smooth; Femur with tubular shape, slightly narrowed distally, and with a meso-medial spine and with two small ectal spines ( Fig. 3 F ). Patella is short, clavate, strongly swollen distally, with a strong meso-distal spine. Tibia armed with one ventro-basal spine and with three ectal and three mesal ventral spines ( Fig. 3 E ). Tarsus mesal and ectally with two spines on each side ( Fig. 3 E ).

Legs: Tubular ( Fig. 4 A ). Coxa IV unarmed. Femur IV with a row of tubercles ( Fig. 4 A ); patella I–III short and swollen; patella IV armed with granules; tibia IV with a retrolateral row of pointed strong tubercles ( Fig. 4 B ); tarsi III and IV with scopula ( Figs 4 C–E ). Tarsal formula: 7(3):15(3):6:6.

Color (specimen preserved in 80% ethanol): Body yellowish. Mesotergal areas, with faint brown reticulations ( Fig. 1 ).

Genitalia: Penis with pars basalis and pars distalis easily distinguishable. Pars basalis tubular slightly thickened distally while pars distalis is slightly flattened dorsoventrally ( Figs 5 A–B, E–F ). Pars distalis with a lamina apicalis ending in two flattened triangular halves. The halves are apically rounded and separated by a deep and narrow groove ( Figs 5 C, G ). Latero-ventral border of pars distalis armed with 8 pairs of leaf-like macrosetae and 2 subapical pairs of truncated setae, also the cuticle has a rugose (folding) appearance ( Figs 5 B, F ). Dorsally, the capsula externa has two small titillators, which present a small crease towards the dorsal region. Inner surface of titillators covered by digitiform projections ( Figs 5 A–B ). Capsula interna with two laminar conductors bearing an also laminar and pointed stylus with a ventral subapical opening of ductus ejaculatorius ( Fig. 5 D ). The cuticular area of the lateral macrosetae has a rugose (folding) appearance ( Fig. 5 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 the copulation. These putative expansible areas could functionally correspond to the spongy body (‘Schwellkörper’ in Martens 1978) commonly observed in Asian biantids.

Female (paratype, MNRJ 2692): measurements as in Table 1 . Similar to male in relation to the armature of the dorsal scutum ( Figs 6 A, C ). Sexual dimorphism evident in tibia IV: females without retrolateral granules. ( Figs 6 B, D ).

Variation. Measurement (minimum-maximum) ( Table 1 ): Males (n=2): total body length (2.15–2.39), carapace length (0.72–0.89), mesotergal length (2.05–2.27), carapace maximum width (1.24–1.27), mesotergal scutum maximum width (1.65–1.70), leg I (5.89–6.24), leg II (11.27–11.73), leg III (7.70–7.76), leg IV (9.22–9.58); Females (n=5): total body length (2.39–2.75), carapace length (0.70–0.78), mesotergal length (1.90–2.13), carapace maximum width (1.12–1.20), mesotergal scutum maximum width (1.55–1.60), leg I (4.51–5.21), leg II (9.19–9.54), leg III (6.02–6.26), leg IV (7.51–8.10). Tarsal formula (n=7): 6–7(3):10–15(3):6:6.

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

Figures

FIGURES 1A–C. Stenostygnus martensi spec. nov., male (holotype, MIZA 0103460), habitus (A dorsal, B ventral, C lateral). Scale bars: 1 mm.

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 4A–E. Stenostygnus martensi spec. nov., male (paratype, MNRJ 2692), right leg IV (A retrolateral, B detail of patella and tibia, C detail of tarsus, D detail of frontal scopula, E detail of lateral scopula). Scale bars: A= 1mm; B= 500µm; C= 200µm; D= 100µm; E= 50µm.

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 6A–D. Stenostygnus martensi spec. nov., sexual dimorphism (A–B female paratype, MNRJ 2692, C–D holotype male, MIZA 0103460). A, C Dorsal view. B, D Detail of tibia. Scale bars: A, C= 2 mm; B, D= 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).

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.