Gymnobisium hogsbackense Neethling & Neethling 2023, sp. nov.

Gymnobisium hogsbackense sp. nov.

Figs 11–13

Holotype: ♀, SOUTH AFRICA, Eastern Cape, Hogsback, Hogsback State Forest, 32°36′S, 26°55′E, 1174m a.s.l., Afromontane forest, Leaf litter sifting, leg. J.A. Neethling, 20.III.2013 (NMBAP 00341).

Paratype: ♂, Same data as holotype (NMBAP 00340).

Etymology. Hogsbackense refers to the type locality of this species, Hogsback, and is in honour of the indigenous Afromontane forest in the area that has high levels of biodiversity.

Diagnosis. Moderately sized species (chela length ♀ 1.46–1.49 mm, ♂ 1.38 –1.41 mm), with chelae distinctly and significantly more bulbous in females than in males (chela ratio ♀ 2.98–3.04 versus ♂ 3.71 –3.94 times longer than broad); fixed finger multi-toothed structure with seven strongly sclerotized teeth; cheliceral hand with five setae; galea with six rami; rallum with eight blades. Differs from all congeners, except Gymnobisium capense sp. nov., by having seven teeth on the fixed finger multi-toothed structure; differs from G. capense sp. nov. by lacking an extra basal seta on the cheliceral hand.

Description

Carapace: Somewhat longer than broad, subquadrate, overall smooth and without furrow. Light or pale brown in both sexes, slightly darker in males. Two pairs of eyes located dorso-laterally at the front. Small seta located on the dorso-anterior margin of each of the posterior eyes. The carapace of both sexes with 20 setae, arranged 4: 4: 4: 2: 6.

Abdomen: Elongate and mostly of uniform width. Tergites and sternites smooth, undivided and uniseriate. Abdominal tergites uniformly light brown in both sexes, slightly darker in males (Fig. 11A, C). In both sexes the posterior margin of tergite I–XI presents a thin, slightly darker band. Tergal setae located on the posterior edge of each tergite within the darkened band. In both sternites remain mostly uniform in colour across the abdomen (Fig. 11B, D). In females the sternites are light brown and in some specimens almost translucent. Male sternites also light brown in colour, lighter than male tergites and somewhat darker than the female sternites, and remain uniformly coloured across the abdomen. Some male specimens present slightly darker posterior sternites. Sternites I and II are fused and hardly distinguishable. Female operculum with 15 setae, six along the posterior margin of sternites II, and seven additional setae clustered loosely alongside, near the centre. Males with 21 setae at the operculum cluster, nine centrally along the poster margin of sternites II, 12 clustered centrally alongside. Male sternites III with 19 small setae situated, in two loose rows, centrally along the anterior margin at the genital opening. Pleural membrane of both sexes cream in colour, faintly papillate.

Tergal chaetotaxy: 6(8): 9(12): 10(12): 12(12): 12(11): 12(12): 12(12): 12(11): 11(12): 8(9): 10(10): 2(2). Sternal chaetotaxy: 15(21):?(?): 20(20): 20(17): 18(16): 15(15): 15(14): 13(14): 13(13): 12(13): 10(10): 2(2).

Pedipalp: All segments smooth and coloured orange-brown in both sexes. Trochanter cone-shaped and rounded anteriorly, curved slightly posteriorly. Base narrow, widening distally. Setae present on the anterior surface. Femur slender, 3.11–3.25 (♀) to 3.36–3.54 (♂) times longer than wide, somewhat constricted basally, widening just distal of base. Deep disto-prolateral excavation present. Setae absent from base, though distributed evenly over rest of surface. Patella constricted and slightly angled at base, widening markedly in females, less in males, at around quarter segment length from base, 2.44–2.61 (♀) to 3.08–3.17 (♂) times longer than wide. This gives female patellae a much thicker appearance, while male patellae appear more as elongate tapered cones. Several small lyriform fissures present on the dorsal surface, just distal of base. One to two larger lyriform fissures present latero-dorsally from these, where the segment starts to widen. Disto-prolateral excavation present and deeper on female patellae. Setae sparse at base, more numerous on wide part of patella.

Chela: In both sexes smooth and uniformly orange-brown, fingers may be slightly darker. Female hand significantly more bulbous, strongly convex on the prolateral edge, slightly less so on the retrolateral edge (Fig. 13D). Male hand much thinner, markedly less convex prolaterally (Fig. 13E). Pedicel taller than wide and short in females (Fig. 12A, B), markedly longer and more rounded in males (Fig. 12C, D), retrolateral condyle small but distinct and rounded. Female chelal fingers thicker, shorter than hand (without pedicel), while male fingers are narrow and longer than hand (without pedicel). Fingers curved slightly prolaterally in both sexes. Fixed and movable chelal fingers with eight and four trichobothria respectively (Fig. 13A).

Terminal multi-toothed structure of fixed finger extends beyond venom tooth of movable finger in both sexes, bent slightly downward, thicker in females, more slender in males. In both sexes, this structure contains seven strongly sclerotized teeth; front tooth with a minute protuberance on the retrolateral surface (Fig. 13C). Proximal and just prolateral of the larger front tooth, five smaller, raised teeth located in a straight line, followed by a larger tooth situated retrolaterally on the structures surface. Both fingers with rounded, juxtadentate teeth situated on flexible lamellae. Lamella on fixed finger of female chela originating roughly one fifth finger length from base, originating roughly midway on movable finger. On male chela, lamellae originate midway on both fingers. Female fixed finger with 49–50 lightly sclerotized, juxtadentate teeth, eight to nine proximal to lamella base, together with seven strongly sclerotized teeth on distal structure. Male fixed finger with 50–51 lightly sclerotized, juxtadentate teeth, 20–22 proximal to lamella base, together with seven strongly sclerotized teeth on distal structure. Female movable finger with 44–46 lightly sclerotized, juxtadentate teeth, 16–17 proximal to lamella base. Male movable finger with 44–46 lightly sclerotized, juxtadentate teeth, 20–22 proximal to lamella base. Two thickened, spine-like setae present on distal end of movable finger in both sexes.

Chelicera: Hand with five long and acuminate setae, es shorter (Fig. 13F). Female fixed finger with 13 teeth, male with 11. Female moveable finger with ten teeth, male with eight. Galea of both sexes divided into two major rami, each terminating in three smaller rami (Fig. 13B). Rallum of both sexes with eight long, acuminate blades (Fig. 13G). Lamina exterior absent in both sexes.

Coxae and legs: Pedipalpal coxae same colour, or slightly lighter than rest of pedipalps. Coxae I–IV tan. Legs I–IV light brown to tan in colour. All legs diplotarsate with subterminal tarsal setae dentate distally; claws simple; arolium shorter than claws.

Measurements (mm): Body length ♀ 2.19– 2.29 ♂ 2.16–2.31; Carapace ♀ 0.74–0.79 x 0.67–0.71 (1.10–1.11) ♂ 0.64 –0.67 x 0.57–0.61 (1.10–1.12); Chelicera ♀ 0.50–0.52 x 0.24–0.26 (2.00–2.08) ♂ 0.40 –0.43 x 0.22 (1.82– 1.95), movable finger length ♀ 0.30– 0.31 ♂ 0.25–0.26; Pedipalps: femur ♀ 0.78–0.81 x 0.24–0.26 (3.11–3.25) ♂ 0.74 –0.78 x 0.22 (3.36–3.54), patella ♀ 0.73–0.78 x 0.28–0.32 (2.44–2.61) ♂ 0.76 –0.80 x 0.24–0.26 (3.08–3.17), chela ♀ 1.46–1.49 x 0.49 (2.98–3.04) ♂ 1.38 –1.41 x 0.35–0.38 (3.71–3.94), hand ♀ 0.87 x 0.49 (1.77) ♂ 0.74 –0.77 x 0.35–0.38 (2.03–2.11), movable finger length ♀ 0.65– 0.66 ♂ 0.61–0.62; Leg I: femur ♀ 0.38–0.40 x 0.09–0.10 (4.00–4.22) ♂ 0.36 –0.37 x 0.09–0.10 (3.70–4.00), patella ♀ 0.27–0.30 x 0.09–0.10 (2.70–3.00) ♂ 0.26 –0.29 x 0.09 (2.89–3.22), tibia ♀ 0.35–0.37 x 0.08–0.09 (4.11–4.37) ♂ 0.34 –0.36 x 0.08 (4.25–4.50), metatarsus ♀ 0.19–0.20 x 0.06 (3.17–3.33) ♂ 0.18 –0.20 x 0.06 (3.00–3.33), tarsus ♀ 0.25–0.26 x 0.05 (5.00–5.20) ♂ 0.21 –0.24 x 0.05 (4.20–4.80); Leg IV femoropatella ♀ 0.67–0.73 x 0.16–0.17 (4.19–4.29) ♂ 0.67 –0.70 x 0.15–0.17 (4.12–4.47), tibia ♀ 0.55–0.64 x 0.10–0.12 (5.33–5.50) ♂ 0.59 –0.63 x 0.10–0.11 (5.73–5.90), metatarsus ♀ 0.21–0.25 x 0.08 (2.62–3.12) ♂ 0.24 x 0.07 (3.43), tarsus ♀ 0.32–0.35 x 0.06 (5.33–5.83) ♂ 0.31 –0.33 x 0.06 (5.17–5.50).

Remarks. Both Gymnobisium cuneatum sp. nov. and G. hogsbackense sp. nov. have, so far, only been collected at the type locality, lending further support to the indigenous Afromontane forests of Hogsback being an endemism hotspot. Harvey et al. (2016) provided sequence data for specimens from Hogsback that can likely be referred to this species. The reason is that G. cuneatum sp. nov. was sampled only from the indigenous state forest, located along the mountain side, while G. hogsbackense specimens were also sampled in the pine plantation, located close to the sampling site of the specimens referred to in Harvey et al. (2016).

Additional material examined. SOUTH AFRICA: Eastern Cape: 2♀, 1♂, 1 Tritonymph, Hogsback, Hogsback State Forest, 32°36′S, 26°56′E, 1080m a.s.l., Afromontane forest, Leaf litter sifting, leg. J.A. Neethling, 20.III.2013 (NMBAP 00327); 1♀, 4♂, Same location, Pine Plantation, 32°35′S, 26°56′E, 1201m a.s.l., Pine plantation, Leaf litter sifting, leg. U.F.S. Entomology Students, 21.III.2013 (NMBAP 00232).