Brachistosternus llullaillaco, Ojanguren-Affilastro & Alfaro & Pizarro-Araya, 2021

Ojanguren-Affilastro, Andrés A., Alfaro, Fermín M. & Pizarro-Araya, Jaime, 2021, Two new scorpion species from protected areas in Antofagasta Region, Chile (Scorpiones, Bothriuridae, Brachistosternus), Zootaxa 5040 (1), pp. 111-131 : 121-129

Brachistosternus llullaillaco n. sp.

( Figs. 1 , 2B, C, D , 6C, D , 7 , 8 , 9A–C, E–G ; Table 1)

Zoobank registration: urn:lsid:zoobank.org:act:96117DA5-6828-4F0D-9673-162C866B1445

Type Material. Holotype male: Chile, Antofagasta Region, Llullaillaco National Park : CONAF refuge, 4157 m asl, (24°37’17.1” S; 68°37’14.8” W), III/2018, A.A. Ojanguren-Affilastro, J. Pizarro-Araya, F.M. Alfaro, A. Castex ( MNHN) . Paratypes: (same data as holotype) , 2 male, 2 females ( MACN) , 1 male, 2 females, 4 juveniles ( LEULS); (24°36’41.0” S; 68°35’06.8” W), 4196 m asl, III /2018 , 1 male, 2 females, 1 juvenile ( MZUC); (24°34’31.1” S; 68°37’22.8” W), 4078 m asl, III /2018 , 1 male, 2 females, 5 juvenile ( MACN); (24°33’43.23” S; 68°37’18.41” W), 4105 m asl, III /2018 , 1 male, 2 females, 10 juvenile ( LEULS) .

Etymology. The specific name, llullaillaco , is a noun in apposition referring to the Llullaillaco Volcano, the second highest active volcano in the world (6739 m asl), and type locality of this species.

Diagnosis. Brachistosternus llullaillaco n. sp. is a member of the subgenus Brachistosternus because of the trichobothrial pattern ( Figs. 8A–G ) and the shape of the hemispermatophore ( Figs. 6C, D ) ( Ojanguren-Affilastro & Ramirez 2009).

Brachistosternus llullaillaco n. sp. is a typical high altitude Andean species of genus Brachistosternus , all of which share a very similar external morphology with medium sized androvestigia ( Fig. 9E ), dark pigment pattern ( Fig. 2D ), and poorly developed pedipalp carinae ( Figs. 8A–G ), and a very similar spermatophore ( Figs. 6C, D ) without Internal Spines and with a Distal Lamina similar in length to the basal portion ( Ojanguren-Affilastro et al. 2016b). This species is most similar to Brachistosternus kovariki Ojanguren-Affilastro, 2003 , another high altitude Andean species from southern Antofagasta Region ( Ojanguren-Affilastro 2003), with which it shares a similar metasomal and pedipalp carination ( Figs. 8A–G , 9E–H ) similar metasomal count of setae ( Figs. 9C, D, F ) and a similar hemispermatophore ( Figs. 6C, D ). Both species can be separated by the pigment pattern of metasoma: in segments I-III, B. llullaillaco n. sp. bears two wide VL dark stripes and a VM dark stripe which is usually wider in its median part and joins with the VL stripes in the posterior third of metasomal segment III ( Fig. 7B ); whereas in B. kovariki the median dark stripe is wider in the anterior margin, narrower towards the posterior margin, and does not join with the VL dark stripes in the posterior margin of segments I-III. Additionally tergites I-VI of B. llullaillaco n. sp. bear a single transversal dark stripe covering the anterior two thirds of the segment ( Figs. 7A, C ); whereas tergites of B. kovariki bear three dark spots, two dorsolateral and one dorsomedian. Both species can also be separated because the ventrolateral setae of metasomal segments I-III are placed in very deep and conspicuous excavations of the tegument in adult specimens of B. llullaillaco n. sp. ( Fig. 9C ), whereas in B. kovariki they are placed in much more shallow excavations ( Fig. 9D ). Finally the tegument around the androvestigia is clearly protruding in B. llullaillaco n. sp., so that the segment is dorso-laterally elevated ( Fig. 9G ) and the glands are placed in an excavation ( Fig. 9E ), whereas in B. kovariki the tegument around androvestigia is not protruding ( Fig. 9H ) and the glands are at the same level of the rest of the dorsal margin.

Brachistosternus llullaillaco n. sp. occurs in parapatry with B. prendinii , which occurs in the same area but at lower altitudes ( Ojanguren-Affilastro 2003). Both species can be separated by the number of ventral setae of metasomal segment V, which range from 19 to 26 in B. prendinii , whereas in B. llullaillaco n. sp. they range from 10 to 12 ( Fig. 9F ). The VM carina of metasomal segment V is restricted to the posterior half of the segment in B prendinii , whereas in B. llullaillaco n. sp. it occupies the posterior two thirds of the segment ( Fig. 9F ). Additionally the Distal Lamina of the hemispermatophore is shorter than the basal portion in B. prendinii , whereas in B. llullaillaco n. sp. it is similar or slightly larger than the basal portion ( Figs. 6C, D ).

Brachistosternus llullaillaco n. sp. is also morphologically similar to Brachistosternus quiscapata Ochoa & Acosta 2002 , from intermediate altitudes of northern Chile and southern Peru ( Ochoa & Acosta 2002; Ojanguren- Affilastro 2003). Both species share a similar pigment pattern and external morphology, but can be easily separated by the shape of the androvestigia which are on the same level as the rest of the tegument in B. quiscapata , but placed in a conspicuous excavation in B. llullaillaco n. sp. ( Figs. 9A, G ). Additionally B. llullaillaco n. sp. bears 10 to 12 ventral macrosetae in metasomal segment V ( Fig. 9F ), whereas B. quiscapata bears 12 to 17.

Description. Based on the holotype male (MNHN) and paratypes (MACN, LEULS, MZUC). Total length, males: 43–67 mm, (N=7; mean= 52.43 mm); females: 43–62 mm, (N=8; mean= 53.13 mm). (Measurements of male holotype and a female paratype in Table 1).

Colour: Base colour dark yellowish, with dark brown pigmentation pattern in pedipalps, carapace, tergites, metasoma and legs; the remaining yellowish without dark spots ( Figs. 2D , 7 ). Chelicerae with dense reticular pigmentation on the anterior margin of manus, the external margin of movable finger, and the internal margin of fixed finger. Carapace, anterior margin with faint pigment, area surrounding the lateral ocelli black, with two broad dark stripes from the postocular furrow to the anterior margin but not reaching it, ocular tubercle black, lateral and postero-lateral margins with dense reticular pigment pattern. Tergites I–VI each with a single transverse dark stripe that covers most of each segment; tergite VII with an anteromedian triangular dark spot, two lateral dark spots and two posterolateral dark spots. Sternites, sternum, genital opercula and pectines unpigmented. Metasomal segments I-III: dorsal surface with two dark spots in the articulation, a median elongated dark spot, and two posterolateral dark spots; lateral surfaces pigmented in the posterior half of the segment, between LM and LIM carinae; ventral surface with two VL dark stripes and a median wide dark stripe, all of them getting wider near the posterior margin and fusing in posterior margin of segment III (in some specimens also fusing in segment II, but never fusing in segment I); segment IV dorsal surface with two dark spots in the articulation, and a median thin dark spot, lateral margins unpigmented, ventral surface as in segment III but more densely pigmented; segment V: dorsal surface with two dark spots in the articulation, rest of dorsal and lateral margins unpigmented, except for some faint pigment near the posterior margin, ventrally with VSM and a VL dark stripes fusing in the posterior half of the segment and forming a wide VL, with a thin VM dark stripe fusing with the lateral dark stripes near the posterior margin. Telson , vesicle with faint pigment pattern in the ventral margin, the rest unpigmented; aculeus dark brown. Pedipalps: trochanter with faint reticular pigment pattern; femur with well-developed dark stripes along DI, DE, and VE margins, with DI and DE stripes joining in a big dark dorsal spot occupying almost half of the dorsal surface near the articulation with patella. Patella, with dorsointernal and dorsoexternal dark stripes, connected to each other by reticulate pattern on the dorsal surface; internal surface densely pigmented in the dorsal half, ventral surface unpigmented. Chela with faint reticular dark stripes along DI, DM, DS, D, E, V and VM carinae; area near articulation of movable finger with faint pigment. Legs: coxae and trochanters unpigmented; femora densely pigmented near articulation with patella; patellae pigmented along external and dorsal margins; tibiae with faint pigment pattern along external and dorsal margins, basitarsi, and telotarsi unpigmented.

Chelicerae: Anterior margin of movable fingers strongly curved; movable fingers with two small subdistal teeth, basal one slightly bigger.

Pedipalps: Femur with DI, DE and VI carinae, granular, extending the entire length of the segment, with two DE macrosetae ( Fig. 8G ); anterior margin with few scattered granules and two macrosetae; rest of the intercarinal surfaces smooth. Patella, DI and VI carinae formed by a few scattered granules, remaining surfaces smooth ( Fig. 8F ); with one DI and two VI macrosetae. Chela manus ( Figs. 8A–E ) robust, length/width ratio, males: 3.40–4.04 (N=7; mean=3.67), females: 3.89–4.56 (N=7; mean=4.15); length/height, males: 2.79–3.20 (N=7; mean=2.93); females: 3.01–3.45 (N=7; mean=3.14); with a blunt VM accessory carina, internal surface with slight bulge near articulation of movable finger in females ( Fig. 8E ), or with a pronounced, subtriangular projection in males ( Figs. 8A, B, D ); fingers elongated, with a median row of denticles; fixed fingers with six pairs of accessory denticles; movable finger with five external accessory denticles and seven internal accessory denticles; the basal external denticle is usually part of the median row. Trichobothrial pattern neobothriotaxic major Type C, with one accessory trichobothrium in V series of chela; femur with 3 trichobothria (d, i, e), one macroseta (M1) between with d and i; patella with 19 trichobothria (2 d, i, 3 et, est, 2 em, 2 esb, 5 eb, 3 V), with esb 2 petite; chela with 27 trichobothria (Dt, Db, 5 Et, Est, Esb, 3 Eb, dt, dst, dsb, db, et, est, esb, eb, ib, it, 5 V), with Et 4 petite, Esb forming triangle with Eb 2 and Eb 3.

Carapace: Anterior margin almost straight, with four setae and a medium sized median projection. Surface: finely granular in the dorsal median area, lateral and posterior margins densely granular, more so in males. Anterior longitudinal sulcus, posterior longitudinal sulcus, and lateral sulci present and well developed. Median ocular tubercle well developed, placed in the middle of the carapace; interocular sulcus shallow; median ocelli well developed, facing towards the lateral margins, ca two diameters apart, with one seta behind each eye. Lateral ocelli pattern type 3A; with three small lateral ocelli on each side of carapace, two of them anteriorly, third ocellus similar in size to the other two, about one diameter above them.

Legs: Surfaces smooth, except for the dorsal and external surfaces of femorae III and IV which are slightly granular. Basitarsi each with two well developed pedal spurs, the internal one 50% smaller than the external one in legs I and II, about 30 % smaller in leg III, symmetrical in leg IV. Telotarsi elongated, ventrolaterally compressed, dorsally with a row of setae, ventrally with a ventromedian row of scarce and strongly reduced hyaline setae, and paired rows of ventrosubmedian setae. Counts of setae on telotarsus III: dorsal setae: 9–11 (N=10; median=10); ventrosubmedian prolateral setae: 5–7 (N=10; median=6); ventrosubmedian retrolateral setae: 4–5 (N=10; median=4). Ungues shallowly curved and short, clearly asymmetrical in legs I and II, being the internal one almost twice bigger than the external in leg I, about 30 % longer in leg II, and being both similar in length in legs III and IV.

Pectines: Well developed. Tooth count, males: 28–32 (N=7; median=32); females: 23–26 (N=7; median=23).

Sternum: With two conspicuous subtriangular lateral lobes, each with a macroseta similar to remaining ventral macroseta.

Genital opercula: Sclerites subtriangular, with an external excavation.

Tergites: I–VI: With two anterior dorsosubmedian setae; surface smooth, only finely granular in the posterior margin; tergite VII with two anterior dorsosubmedian setae, lateral and posterior margins granular; with two barely visible dorsosubmedian carinae in the posterior third of the segment and two lateral carinae in the posterior half of the segment.

Sternites: Surface finely granular in males, smooth in females; sternites III–VI with large and elongated spiracles and small and deep ventrosubmedian furrows.

Metasoma: Metasomal segment I, dorsal surface densely granular, except for the area next to the median sulcus that is smooth; DL carinae formed by a barely visible row of granules, and extending the entire length of the segment; lateral surfaces granular between DL and LM carinae, smooth between LM and LIM carinae; LM and LIM carinae extending the posterior two thirds of the segment; with one LM seta in the middle of the segment and one LIM macroseta in the posterior third of the segment; ventrally granular in males, smooth in females, without carinae, with 2-2 VL setae placed in deep conspicuous excavations ( Fig. 9C ), and 2 posterior VSM setae. Metasomal segments II and III similar to segment I but less granular and with the LIM carinae only present in the posterior third of the segment. Metasomal segment IV, dorsal surface smooth; DL carina well developed formed by some blunt granules, extending the entire length of the segment, with one DL macroseta; lateral margins granular above LM carinae, LM carinae represented by an elevation of the tegument and two LM macrosetae; accessory carinae poorly developed; smooth below LM carinae; LIM carinae absent; ventral surface smooth, with 28–34 scattered setae. Metasomal segment V comparatively stout; length/width ratio, males: 1.70–1.93 (N=7; mean=1.83); females: 1.76– 2.00 (N=7; mean=1.87); dorsal surface smooth, males with two well-developed glands or androvestigia placed in the anterior half of the segment, and occupying about half of the length of it, these glands are placed in a conspicuous elevation of the tegument ( Fig. 9G ) so that there is a well-developed median dorsal furrow between them ( Fig. 9E ); DL carinae well developed extending the entire length of the segment in males, barely visible in females, with one DL setae; lateral margin granular in the dorsal half and smooth in the basal half in males, completely smooth in females; LM carinae inconspicuous, represented by a row of 5–7 macrosetae extending the entire length of the segment; LIM carinae absent, VL carinae well developed and extending the entire length of the segment, with 9–10 VL macrosetae; ventral surface finely granular, more so in the posterior third of the segment ( Fig. 9F ), VM carina extending the entire length of the segment, ventral macrosetae arranged in four transverse rows, two near the anterior margin of four (sometimes two) macrosetae, and two rows of two macrosetae each near the posterior margin (4-4-2-2 or 4-2-2-2).

Telson: Vesicle globose ( Fig. 9A ), slightly more globose in females ( Fig. 9B ); length/height ratio, males: 2.57– 3.04 (N=7; mean=2.88); females: 2.70–3.03 (N=7; mean=2.88); ventral surface granular, more so in males; lateral margins with a shallow furrow; dorsal surface smooth and shallow, in males there is a conspicuous glandular subtriangular surface. Aculeus similar in size to the vesicle, shallowly curved.

Hemispermatophore: Basal Portion well developed. Distal Lamina well developed, only slightly curved medially ( Fig. 6D ), similar in length or slightly longer to the basal portion; distal lobe (distal posterior flexure) medium sized, occupying less than a quarter of the distal lamina, distal crest medium sized extending more than a third of the distal lamina, without transverse crests and placed very close to the posterior margin; left hemispermatophore: cylindrical apophysis of the basal lobe well developed ( Fig. 6C ), of a similar thickness in most of its length, and with a curved acute tip barely reaching the base of the distal lobe, and slightly longer than the laminar apophysis; laminar apophysis bilobed, with a median internal longitudinal flexure that divides it into two lobes; row of spines and basal spines well developed and in the same line, internal spines absent; basal triangle medium sized, formed by three chitinous crests. Right hemispermatophore without a cylindrical apophysis, instead there is a small Internal Laminar Apophysis (ILA) poorly chitinized, with spines in its dorsal and external margins, being the basal spines of the row of spines twice bigger than the apical ones; the rest as left hemispermatophore.

Distribution. Brachistosternus llullaillaco n. sp. has only been collected in a small area of very high altitudes of the Llullaillaco National Park, in Antofagasta Region, Chile, between 4000–4200 m asl, in the western slopes of the Llullaillaco Volcano ( Figs. 1 , 2C ).

Ecology. Brachistosternus llullaillaco n. sp. has been collected in a zone of transition between winter and summer rains ( Arroyo et al. 1998), which belongs to the Montane Desert of the “Cordillera de Domeyko”. This is a low coverage desertic shrub steppe formed mostly by Atriplex atacamensis Philippi 1860 , Atriplex deserticola Philippi 1860 , Acantholippia trifida (Gay) Moldenke 1940 , Acaena canescens Philippi 1860 , Lycium minutiflorum Dammer 1915 , Adesmia atacamensis Philippi 1860 , Coldenia atacamensis Philippi 1860 , Atriplex microphylla (Thunb.) Willd. 1806 , Cristaria andicola Gay 1846 and Fabiana bryoides Philippi 1860 (CONAF 1999, Marticorena 2004, Peñaloza et al. 2013).

Brachistosternus llullaillaco n. sp. has not been collected in sympatry with any other scorpion species, but in parapatry with B. prendinii , which occupies the immediate lower level of altitude in the area, between 3700-4000 m asl. Brachistosternus prendinii is also known from a close locality (about 230 km north) near San Pedro de Atacama ( Ojanguren-Affilastro 2003), where it has been collected at lower heights than in the Llullaillaco area, between 2800-3200 m asl. In San Pedro de Atacama, above 3200 m asl B. prendinii is replaced by B. kovariki , a very close species to B. llullaillaco n. sp. The presence of the same species at lower altitudes, but different species at higher altitudes, in such a small range, could reflect a higher degree of speciation at higher altitudes in the Andes due to the isolation of these extreme high altitude populations ( Ceccarelli et al. 2016); whereas other high Andean species occurring at slightly lower altitudes could have a higher degree of connection between populations favored by the continuity between lower mountain ranges. It is also interesting to note that the altitudinal range of B. prendinii is slightly different in Llullaillaco respect to San Pedro de Atacama; this could be related to different local environmental conditions, or to different interactions between B. kovariki and B. llullaillaco n. sp. with B. prendinii . More field work in the area would be necessary to unveil these questions.

All known specimens of B. llullaillaco n. sp. have been collected in late summer, and we could even find some specimens mating in march ( Fig. 2B ), which suggests that this species has a summer activity period as all known Andean species of Brachistosternus ( Ojanguren-Affilastro et al. 2018) .

Llullaillaco National Park is placed in an area of high inter-annual rainfall fluctuations ( Huston & Hartley 2003), where the “El Niño” Southern Oscillation (ENSO) cycle defines the emergence of several plants of the area ( Latorre et al. 2003). This particular situation has a direct impact in the presence and cyclical appearance of preys for arthropod predators, such as scorpions, therefore also defining their presence and distribution in the area.

Figures

FIGURE 1. Distribution map of Brachistosternus chimba n. sp. (white circles), and Brachistosternus llullaillaco n. sp (white triangles); SNASPE: National System of Protected Wild Areas (by its acronym in Spanish).

FIGURES 2A–F. Living specimens and type localities of Brachistosternus species herein described. A. Brachistosternus chimba n. sp.; B. Couple of Brachistosternus llullaillaco n. sp. mating under UV light; C. Llullalillaco Volcano, type locality of Brachistosternus llullaillaco n. sp.; D. Brachistosternus llullaillaco n. sp.; E, F. La Chimba National Reserve, type locality of Brachistosternus chimba n. sp., E. Internal area in La Chimba ravine, F. Eastern external area facing the Chilean Coast Range.

FIGURES 6A–D. Left hemispermatophore of Brachistosternus species herein described. A, B. Brachistosternus chimba n. sp. A. Internal aspect. B. External aspect. C, D. Brachistosternus llullaillaco n. sp. C. Internal aspect. D. External aspect. Scale bars: 1mm.

FIGURES 7A–D. Brachistosternus llullaillaco n. sp., habitus. A. Male, dorsal aspect; B. Male, ventral aspect; C. Female, dorsal aspect; D. Female, ventral aspect. Scale bars: 1 cm.

FIGURES 8A–G. Brachistosternus llullaillaco n. sp. A. Left pedipalp chela, male, internal aspect; B. Left pedipalp chela, male, dorsal aspect; C. Left pedipalp chela, male, external aspect; D. Left pedipalp chela, male, ventral aspect; E. Left pedipalp chela, female, ventrointernal aspect; F. Left pedipalp patella, male, external aspect. G. Left pedipalp femur, male, dorsal aspect. White circles mark the position of each trichobothrium. Scale bars: 1mm.

FIGURES 9A–C, E–G. Brachistosternus llullaillaco n. sp. A. Telson, male, lateral aspect; B. Telson, female, lateral aspect; C. Metasomal segments I and II, ventral aspect; E. Metasomal segment V, male, dorsal aspect; F. Metasomal segment V, male, ventral aspect; G. Metasomal segment V, male, lateral aspect. D, H. Brachistosternus kovariki. D. Metasomal segments I and II, ventral aspect; H. Metasomal segment V, male, lateral aspect. Scale bars: 1mm.