Type Material

Holotype: 1 juv. ♂ (IAvH-E 100809): COLOMBIA: Nariño Department: Municipio de Ricaurte: La Planada Natural Reserve, permanent plot, 01°15′N 78°15′W, 1885 m, Winkler trap, 16–20.v.2000, G. Oliva (examined).

New Records

COLOMBIA: Nariño Department: Municipio de Ricaurte: Vereda Alto Cartagena, Finca Nueva Estrella, 01°13′15.7″N 77°58′08.6″W, 1617 m, 12.ix.2008, R. Botero-Trujillo, J.P. Botero and J.A. Ochoa, 1 ♂, 3 ♀, 1 juv. (ICN); 1 ♂, 3 ♀, 1 juv. (MPUJ).

Diagnosis

Troglotayosicus humiculum differs morphologically from T. vachoni, the only other species in the genus, in the following respects. The carapace anterior margin is sublinear, with a weak median projection (epistome; fig. 3B), and there are three pairs of lateral ocelli (the median ocellus is present but greatly reduced) in T. humiculum, whereas the anterior margin is convex, with a pronounced epistome, and there are two pairs of lateral ocelli (the median ocellus is absent) in T. vachoni. The setae on the ventral surfaces of telotarsi I–IV are regularly arranged into a pair of parallel ventrosubmedian rows in T. humiculum (fig. 8), but are irregularly arranged in T. vachoni. The pedipalpal and metasomal carinae differ as follows: four carinae (DI, DE, VI, VE) are evident on the pedipalp femur of T. humiculum (fig. 7C, E), compared with only three carinae (DE, DI and VI) in T. vachoni; at least the DS, DMA and DI carinae are evident, albeit obsolete (identified only by granulation and subtle differences in angles between adjacent surfaces), on the pedipalp chela of T. humiculum (figs. 5, 6), whereas the chela is entirely smooth and acarinate in T. vachoni; the VL carinae of metasomal segments I and II are absent in T. humiculum (fig. 9C) but present in T. vachoni. We have not examined the holotype of T. vachoni, but judging from the original description, the chelicerae, tergites, pectines, trichobothrial pattern, and carination of metasomal segments IV and V appear to be similar in both species. It is impossible to unequivocally identify all petite trichobothria in T. vachoni from Lourenço's (1981) figures 46–52, but the vestigial LSM carinae (fig. 10B, F) are clearly illustrated in Lourenço's (1981) figure 41. The two species also differ markedly in their ecology: T. humiculum is endogean whereas T. vachoni is hypogean.

Description

Based on two adult males, six adult females and two juveniles. Measurements are recorded in table 1.

Color: Base color, chelicerae and legs yellowish (♂ and juveniles) or light chestnut (♀); carapace, tergites, metasoma, and pedipalps yellowish to pale orange (♂ and juveniles) or carapace and pedipalps dark chestnut, becoming slightly darker on tergites and metasomal segments (adult ♀; fig. 1C); sternites and coxosternal region yellowish; pectines whitish. Carapace and pedipalps unpigmented (♂) or with weak brown pigmentation, slightly darker than base color, remaining areas unpigmented (♀).

Chelicerae: Manus, dorsoexternal surfaces smooth, sparsely setose; ventral and internal surfaces densely setose. Fixed finger, dorsal margin with four teeth (distal, subdistal, median, and basal); median and basal teeth separate, not fused into bicusp. Movable finger, internal distal and external distal teeth not opposable, internal distal tooth at most partially overlapping external distal tooth in dorsal view; dorsal margin with four teeth (internal distal, subdistal, median, and basal; fig. 3A); ventral surface with long, well-developed serrula.

Carapace: Anterior margin sublinear, with weak median projection (epistome) and 6–7 macrosetae (fig. 3B); several granules evident along margin immediately anterior to lateral ocelli. Posterior margin sublinear, with few macrosetae. Median ocelli absent; three pairs of lateral ocelli present, anterior pair largest, median pair greatly reduced, posterior pair slightly smaller than anterior pair. Median longitudinal sulcus well developed; posterolateral and posterior transverse sulci obsolete. Surfaces acarinate, mostly smooth, except for fine granulation laterally (more pronounced in ♂); two submedian setae evident in anterior half.

Pedipalps: Femur tetracarinate; DI carina complete, granular; DE carina restricted to proximal two-thirds of segment, granular (fig. 7C); VI carina discontinuous, comprising two or three granules proximally and four or five granules in distal third; VE carina obsolete, restricted to proximal third of segment (♂) or vestigial (♀) (fig. 7E); dorsal and external intercarinal surfaces with few scattered granules; internal surface with five or six prominent granules and four additional granules on proximal margin (less developed in ♀); ventral surface smooth except for few granules in proximal third; all surfaces sparsely setose. Patella tricarinate; DI and VI carinae complete, granular (more so in ♂; fig. 7A, B, F); DPP and VPP each with one or two granules proximally; DE carina restricted to median two-thirds of segment (♂) or absent (♀) (fig. 7A, B); all other carinae absent; intercarinal surfaces smooth. Chela manus very slightly incrassate, fingers shorter than (♂) or subequal to (♀) manus length. Chelal carinae obsolete or absent; DS, DMA and DI carinae identified by granulation and subtle differences in angles between surfaces (more pronounced in ♂; figs. 5, 6); DS carina complete, weakly granular; DMA and DI carinae complete, densely granular; VI carina weakly granular (♂) or smooth (♀); D and E carinae evident only as subtle differences in angles between adjacent surfaces. Manus, intercarinal surfaces smooth, covered with scattered macro- and microsetae, becoming more numerous on fingers. Fixed finger, median denticle row comprising six oblique, slightly imbricate primary subrows of denticles, flanked by six external and five internal denticles; terminal denticle considerably larger than preceding denticles, hooklike, fingertips interlocking unevenly when closed such that movable finger displaced to exterior. Movable finger, median denticle row comprising seven oblique, slightly imbricate primary subrows of denticles, flanked by six external and six internal denticles; terminal denticle enlarged, hooklike, accommodated in subdistal diastema (notch) of fixed finger.

Trichobothria: Femur with three trichobothria (fig. 7C): one external (e), one dorsal (d), one internal (i). Patella with 19 trichobothria (fig. 7B, D, F), two petite (et₂, esb₂), one accessory (em₃): two ventral (v₁, v₂); 14 external (et₁–et₃, est, em₁–em₃, esb₁, esb₂, eb₁–eb₅); two dorsal (d₁, d₂); one internal (i). Chela with 26 trichobothria (figs. 5, 6), five petite (Et₄, Et₅, Esb, Db, dsb), one accessory (dm): 15 on manus, four ventral (V₁–V₄), ten external (Et₁–Et₅, Est, Esb, Eb₁–Eb₃), one dorsal (Db); 11 on fixed finger, four external (et, est, esb, eb), five dorsal (dt, dst, dm, dsb, db), two internal (it, ib). The petite condition of Et₄ in Troglotayosicus is recognized here for the first time and results in a trichobothrial interpretation with greater similarity to typhlochactid species (all of which also exhibit petite Et₄ and Et₅; Vignoli and Prendini, 2009) than that presented by Botero-Trujillo and Francke (2009); see Prendini et al. (2010) for trichobothrial notation in T. humiculum defined strictly on positional homology (the “placeholder approach”).

Legs: Legs I–IV, carination more developed on III and IV than I and II; femur tetracarinate (less pronounced in ♀), VI and EM carinae continuous, granular, DI carina restricted to proximal third, fusing with VI carinae medially; patellar DE carinae continuous (♂) or restricted to distal third (♀), comprising small, sparse granules. Tibia sparsely setose, tibial spurs absent. Basitarsi I–IV setose, each with one dorsal and two or three ventral rows of brushlike spinules distally (fig. 8); dorsal retrolateral brush usually well developed on legs I–III, vestigial on IV; median prolateral brush well developed on I–III, absent on IV; ventral prolateral brush well developed on I and II, absent on III and IV; ventral retrolateral brush obsolete on legs I and II, obsolete or absent III, absent on IV; prolateral pedal spurs present; retrolateral pedal spurs vestigial. Telotarsi I–IV, dorsomedian lobe with one large microseta; ventral surface without spinules, subspiniform setae regularly arranged into pair of parallel ventrosubmedian rows (fig. 8), comprising 5–6 prolateral and 6–7 retrolateral setae on I, 6/7 on II, 7–8/7–8 on III, 8/8–9 on IV; ungues well developed, curved, equal in length; dactyl shorter than ungues.

Tergites: Pretergites smooth. Posttergites I–VI, surfaces finely granular (♂) or almost smooth with sparse, fine granules (♀). Posttergite VII, surface finely granular (more so in ♂), posterior half with scattered granules in position of DSM carinae; DL carinae present in posterior half, each terminating in tubercle comprising four or five granules; posterior margin coarsely granular.

Sternum: Shape subpentagonal with rounded apex and lateral margins converging anteriorly such that posterior width greater than length; posterior depression shallow. Surface with 6–8 macrosetae and several microsetae (fig. 4).

Pectines: Pectinal plate, surface with several macrosetae situated mediolaterally. Lamella comprising five segments. Tooth count, 7–7 in all specimens; proximal and distal teeth slightly larger than others (fig. 4).

Sternites: Sternites III–VI, surfaces smooth, each with pair of small, rounded spiracles, situated mediolaterally; VII, surface smooth, acarinate; III–VII each with transverse row of six macrosetae medially and row of 6–10 (usually 10) macrosetae along posterior margin (fig. 3C).

Metasoma: Segments I–V progressively increasing in length (table 1). Segments I–IV, dorsal and lateral intercarinal surfaces entirely densely and finely granular (♂) or sparsely and finely granular in posterior half only (♀; fig. 9B); ventral intercarinal surfaces smooth on segments I and II, sparsely granular on III, densely and coarsely granular on IV (fig. 9C). Segment V, dorsal intercarinal surfaces sparsely and finely granular; lateral and ventral surfaces densely and coarsely granular, granules increasing in size posteriorly (fig. 10A–C, F). DL carinae complete, costate-granular, converging distally on segments I–IV (fig. 9), complete, granular on V; LSM carinae vestigial, comprising row of small granules between DL and ML carinae, in medial third of segments I–IV, more pronounced on III and IV than on I and II (fig. 9A, B), weakly granular and restricted to medial third of V (fig. 10B); ML carinae complete, costate-granular on segments I–IV, less pronounced on IV, and complete, but obscured by dense granulation on lateral surfaces of V (fig. 10B); LIM carinae less pronounced than DL and LSM carinae, comprising isolated granules, complete on segments I–III, complete or restricted to posterior two-thirds of IV, absent on V; VL and VSM carinae absent on segments I and II, comprising a few granules on III (VSM often absent on III in ♀), and a row of coarse granules in median third of IV; VL, VSM and VM carinae restricted to anterior half of segment V, obscured by scattered granulation in posterior half (fig. 10A, C). DL carinae each with one macroseta on segments I–III, two macrosetae on IV, five (sometimes fourth is a microseta) on V; LM carinae each with one or two macrosetae on segment I, two on II–IV, four on V; LIM carinae each with two macrosetae on segments I–III, three on IV, one situated posteriorly on V; two macrosetae in place of each VL carina on segment I, three on II–IV, five on V; ventral surface, segment I with four transverse macrosetae, II with 3–4, III and IV each with four (usually in two rows), V with 10–12; posterior margin, segments I–IV each with 4–6 additional setae, V with 6–8.

Telson: Vesicle elongated; anterodorsal lateral lobes present (fig. 10D, E); surfaces smooth dorsally and laterally, coarsely granular ventrally; with scattered long macrosetae and several short microsetae. Aculeus long, gently curved.

Hemispermatophore: Lamelliform (fig. 11A–D). Lamina pale and weakly sclerotized, especially distally; apex elongated, without crests, wider medially, conical distally, inclined ventrointernally; dorsal margin, distal half inclined towards ventrointernal surface; ventral margin well developed; articular flexure present; basal portion and foot well developed but weakly sclerotized. Capsule simple; external lobe reduced with a small dorsal process, inclined towards internal surface; internal lobe more pronounced than external lobe, with one sclerotized external spurlike projection. Male specimens of T. vachoni are unknown, but the hemispermatophore of T. humiculum appears most similar to that of the endemic Colombian chactid, Vachoniochactas humboldti Flórez et al., 2008, based on the structure of the capsule (Flórez et al., 2008). The capsular lobes are similarly developed, possessing one or more external spurlike projections on the internal lobe, in both species. However, the shape of the lamina differs in the two species. It is straight and truncated distally in V. humboldti, but inclined towards the ventrointernal surface and narrowed distally in T. humiculum.

Sexual dimorphism: Adult males and females differ in the following proportions (table 1). Total length: ♂, 19.1–19.6 mm (n  =  2); ♀, 18.95–19.90 mm (mean  =  19.19 mm, n  =  6). Pedipalp chela, length/width ratio: ♂, 3.03–3.09 (n  =  2); ♀, 3.15–3.38 (mean  =  3.26, n  =  6); length/height ratio: ♂, 2.77–2.83 (n  =  2); ♀, 2.89–3.19 (mean  =  3.02, n  =  6). Pedipalp femur, length/width ratio: ♂, 2.74–2.94 (n  =  2); ♀, 2.72–2.85 (mean  =  2.78, n  =  6). Metasomal segment I, length/width ratio: ♂, 0.49–0.50 (n  =  2); ♀, 0.46–0.50 (mean  =  0.48, n  =  6). Metasomal segment II, length/width ratio: ♂, 0.58–0.61 (n  =  2); ♀, 0.52–0.56 (mean  =  0.55, n  =  6). Metasomal segment III, length/width ratio: ♂, 0.65–0.66 (n  =  2); ♀, 0.58–0.61 (mean  =  0.60, n  =  6). Metasomal segment IV, length/width ratio: ♂, 0.93–0.95 (n  =  2); ♀, 0.80–0.89 (mean  =  0.84, n  =  6). Metasomal segment V, length/width ratio: ♂, 1.55–1.56 (n  =  2); ♀, 1.35–1.45 (mean  =  1.42, n  =  6). Metasomal segment V, length/height ratio: ♂, 1.97–2.00 (n  =  2); ♀, 1.67–1.94 (mean  =  1.80, n  =  6). Telson, length/height ratio: ♂, 3.57–3.75 (n  =  2); ♀, 3.24–3.60 (mean  =  3.41, n  =  6).

Ontogenetic variation: The pedipalpal and metasomal carinae are more developed in adult specimens than in the juvenile holotype. The adults possess four carinae (DI, DE, VI and VE) on the femur, at least two carinae (DI and VI) on the patella, and at least three (DS, DMA, and DI always granular) on the chela. The carinae of the holotype are obsolete on the femur and absent on the patella and chela. However, in other juveniles examined, the DMA and DI carinae of the chela and the VI carinae of the patella are present but less developed than in adults. Similar differences are evident between the metasomal carination and granulation of adults and juveniles. Metasomal segments III and IV possess VL carinae in adults, but these carinae are absent in juveniles (including the holotype). Metasomal segment V is markedly granular ventrally and laterally in adults, with VM, VSM, and VL carinae evident in the anterior half of the segment and obscured by dense granulation in the posterior half, compared with juveniles (including the holotype) in which ventral granulation is present only in the posterior half. Vestigial LSM carinae are present on metasomal segments III and IV in all specimens (including juveniles), a character not reported in the original description by Botero-Trujillo and Francke (2009). Base coloration also differs between adults and juveniles, varying from dark chestnut in females to yellowish in males and juveniles.

Ecology

Troglotayosicus humiculum is a troglomorphic endogean (humicolous) species, one of only four troglomorphic scorpions known from South America, the others being T. vachoni from Ecuador, the chactid Broteochactas trezzii (Vignoli and Kovarík, 2003) from Venezuela, and the buthid Troglorhopalurus translucidus Lourenço et al., 2004, from Brazil (Vignoli and Kovarík, 2003; Lourenço et al., 2004; Volschenk and Prendini, 2008). The holotype of T. humiculum was collected in a Winkler trap in primary rainforest (Botero-Trujillo and Francke, 2009). The new specimens reported here were collected by hand in a small patch of mountain rainforest (humid premontane forest sensu Holdridge, 1987) surrounded by deforested grassland (fig. 1A). The specimens were captured at night between 21:00 and 02:00 hours by disturbing leaf litter and scanning the disturbed area with UV light. All specimens were taken from underneath a deep layer of leaf litter (10–20 cm below the surface). The area in which they were collected had a very steep slope, and specimens were found only where the greatest amount of leaf litter had accumulated, usually at the base of large trees (fig. 1B). No specimens were observed actively moving, but were always found immobile. Upon detection, they usually remained still for a second before tucking in their appendages and turning the metasoma over the body, allowing them to tumble downslope as an escape strategy. Three other scorpion species, Ananteris dorae Botero-Trujillo, 2008, Tityus cuellari Lourenço, 1994, and Teuthraustes sp., were collected in sympatry with T. humiculum.

Distribution

Troglotayosicus humiculum is currently known only from the Nariño Department of southwestern Colombia (fig. 12). The holotype was collected in La Planada Natural Reserve, at an elevation of 1885 m on the western slopes of the Andes, close to the border with Ecuador. The new specimens of T. humiculum were collected in the Ricaurte Municipality at an elevation of 1617 m. Both records fall within the northwestern Andean montane forests, a region with unusually high diversity and endemism due to the Andean topography and a pronounced period of isolation. Botero-Trujillo and Francke (2009) suggested that La Planada could be a center of scorpion endemism because the three scorpion species described from there (A. dorae, T. cuellari, and T. humiculum) had not been collected elsewhere. This suggestion was falsified by the 2008 expedition to Nariño Department, during which all three species were collected at other localities, suggesting that this region is poorly sampled and the putatively restricted distributions of the three species are a sampling artifact.