Brachistosternus chimba, 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 : 112-121

Brachistosternus chimba n. sp.

( Figs. 1 , 2A, E, F , 3 , 4 , 5 , 6A, B ; Table 1)

Zoobank registration: urn:lsid:zoobank.org:act:A9D5F523-C1D3-421E-B2B3-0DA1C9062E0C

Type Material. Holotype male: Chile, Antofagasta Region, La Chimba National Reserve, Quebrada Los Cactus (23°31’23.87” S, 70°20’27.11” W), 712 m asl, 18/XII/2019. A.A. Ojanguren-Affilastro, J. Pizarro-Araya, F.M. Alfaro, A. Castex ( MNHN) ; Paratypes (same data as holotype) : 1 male, 2 juveniles ( MACN) ; 3 juveniles ( MZUC) , 1 female, 5 juveniles ( LEULS) ; Quebrada La Chimba , La Chimba National Reserve (23°32’20.76” S, 70°21’35.82” W), 402 m asl, 19/XII/2019, A.A. Ojanguren-Affilastro, J. Pizarro-Araya, F.M. Alfaro, A. Castex : 2 females ( MACN) ; 1 female, 2 juveniles ( LEULS) .

Etymology. The name of this species, chimba , is a noun in apposition referring to La Chimba National Reserve, a small protected area nearby Antofagasta city in northern Chile.

Diagnosis. Brachistosternus chimba n. sp. is a member of the subgenus Brachistosternus because of the trichobothrial pattern ( Figs. 4A–G ) and the shape of the hemispermatophore ( Figs. 6A, B ) ( Ojanguren-Affilastro & Ramírez 2009). Brachistosternus chimba n. sp. occurs close to the distribution of Brachistosternus mattonii Ojanguren-Affilas- tro 2005 and Brachistosternus philippii Ojanguren-Affilastro, Ochoa & Pizarro-Araya 2018 ( Ojanguren-Affilastro 2005, Ojanguren-Affilastro et al. 2016 a, 2018), but its morphological features are very different from those of these species of the area. It can be distinguished from both species by its darker color, since B. mattonii and B. philippii are both typical psammophilous species almost completely unpigmented, whereas B. chimba n. sp. is densely pigmented ( Fig. 2A ); by presenting more ventral setae on metasomal segment V, 20-24 in B. chimba n. sp. ( Fig. 5F ), 6-8 in B. mattonii and 6-9 in B. philippii ; by the development of the VM carina in metasomal segment V, which extends the entire length of the segment in B. mattonii and B. philippii , whereas in B. chimba n. sp. it only occupies the posterior half of the segment ( Fig. 5F ); by the absence of internal spines in the hemispermatophore, which are present both in B. mattonii and B. philippii ; and by the shape of the androvestigia, which are placed in the anterior half of the segment being no longer than a quarter of it in B. chimba n. sp. ( Fig. 5G ), whereas in B. mattonii and B. philippii they are placed more medially, and they are narrower and more elongated, being longer than a half of the length of the segment.

Brachistosternus chimba n. sp. resembles more to Brachistosternus prendinii Ojanguren-Affilastro 2003 , a high altitude Andean species from the Antofagasta Region mostly due to its similar metasomal and pedipalp carinae ( Figs. 4A–G ), similar number and distribution of metasomal setae ( Fig. 5F ), and by the shape and development of the structures of the hemispermatophore ( Figs. 6A, B ) ( Ojanguren-Affilastro 2003, Ojanguren-Affilastro et al. 2016b). It can be separated from B. prendinii by having more pectinal teeth, 42-48 in B. chimba n. sp. males ( Fig. 5E ), 33-41 in females, 32-35 in B. prendinii males, 25-30 in females; by having smaller androvestigia, occupying about a third of the length of the segment in B. chimba n. sp. ( Fig. 5 G ), and about a half of it in B. prendinii , and by having more elongated telotarsi which are almost cylindrical or terete ( Figs. 5C, D ), whereas in B. prendinii they are comparatively taller, and clearly compressed laterally, as in most Andean species of the genus ( Ojanguren-Affilastro et al. 2007; Ojanguren-Affilastro et al. 2016b).

Description. Based on the holotype male (MNHN) and paratypes (MACN, LEULS, MZUC). Total length: 59 and 60 mm in both studied adult males; 55, 56 and 61 in three studied adult females (Measurements of male holotype and a female paratype in Table 1).

Colour: Base colour brownish, with dense dark brown, pigmentation pattern in carapace, tergites, metasoma and legs; the remaining segments brownish without dark spots ( Figs. 2A ; 3A–D ). Chelicerae with reticular pigmentation on the base of manus, anterior margin of manus and fingers dark brown. Carapace, anterior margin with faint dark pigment; with two broad dark stripes from the ocular tubercle and the postocular furrow to the lateral ocelli, leaving a triangular poorly pigmented area in the anterior margin; ocular tubercle black; lateral margins with reticular dark pattern, posterior margin with two posterolateral dark spots connecting with the reticular lateral pattern. Tergites I–VI densely pigmented, each with a single transversal dark stripe, leaving one unpigmented lateral internal area on each side and a posterior median unpigmented area; tergite VII with two anterolateral dark spots and a single anteromedian dark spot, posterior half of the segment unpigmented. Sternites, sternum, genital opercula and pectines with brownish base colour but without a pigment pattern. Metasomal segments I-III: dorsal surface with two anterolateral little dark spots in the articulation, a median dark reticular area and two posterolateral little dark spots in the posterior margin, (some specimens are only barely pigmented); lateral surfaces with a dark faint stripe between LM and LIM carinae; ventral surface with two VL dark stripes and a wide VM dark stripe fusing in the posterior margin of the segment, in some specimens the ventral dark stripes of segment I and II are faint or even absent. Metasomal segment IV: similar to segment III but ventral dark stripes more densely pigmented and dorsal and lateral dark spots reduced. Metasomal segment V: dorsally with two posterolateral dark spots in the posterior half of the segment, males with paired median whitish glands; laterally unpigmented; ventral surface with posterior three quarters of the segment with two broad and well-marked VL dark stripes formed by the fusion of VL and VSM stripes, with a VM thin, reticular but well-marked, dark stripe in the anterior two thirds of the segment joining with the VL stripes in the posterior third. Telson: vesicle unpigmented; aculeus dark brown. Pedipalps: trochanter unpigmented; femur dorsally with a DE dark stripe and a dark spot in the distal third, with a VE stripe, and a ventral dark spot in the proximal third, internally pigmented only near the proximal third, mostly in the upper half of the segment. Patella dorsal surface with reticulate pattern, with an external dark stripe and a VE dark stripe connected by reticular pigment, internally densely pigmented in the upper half of the segment. Chela, externally with faint reticular pigment near the base of the manus, fingers completely unpigmented. Legs: coxae and trochanters unpigmented, femora and patellae densely pigmented except for the internal margin which is unpigmented; tibiae, basitarsi and telotarsi unpigmented.

Chelicerae: Anterior margin of movable finger strongly curved in males and females; movable finger with two small subdistal teeth.

Pedipalps: Femur with DI, DE and VI carinae formed by small continuous granules extending the entire length of segment, with two DE macrosetae ( Fig. 4G ); VE carina not conspicuous; anterior margin with few scattered medium sized granules and three macrosetae in the median axis; posterior margin with 6 macrosetae arranged in two longitudinal rows, rest of the intercarinal surfaces smooth. Patella surfaces smooth, DI and VI carinae formed by few scattered tiny granules ( Figs. 4F ); with one DI macroseta and three VI macrosetae. Chela manus slender, slightly more robust in males, length/height ratio: 3.04 and 3.14 in both studied adult males, 3.85, 3.89 and 4.00 in three studied adult females; length/width ratio: 3.66 and 3.82 in both studied adult males, 4.56, 4.85 and 4.91 in three studied adult females; with blunt VM accessory carina, internal surface with slight bulge near articulation of movable finger in females ( Fig. 4E ), or with a pronounced, spiniform, slightly curved projection in males ( Figs. 4A, B, D ); fingers elongated, with a median row of denticles being the basal most twice bigger than the apical, and six or seven pairs of accessory denticles in fixed fingers, and five or six in movable fingers, basal external denticle is usually part of the median row ( Figs. 4A–E ). 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), being 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), being Et 4 petite, Esb forming triangle with Eb 2 and Eb 3.

Carapace: Anterior margin slightly convex, with four setae and a blunt median projection. Surface: finely granular, except for the median dorsal area that is almost smooth. 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 with its anterior margin elevating gradually and its posterior margin ending abruptly, interocular sulcus very deep and well developed, median eyes medium sized facing towards the lateral margins and ca two diameters apart, with one seta behind each median eye. Lateral eyes pattern type 3A; with three small lateral eyes on each side of carapace, two of them placed anteriorly, the anterior one slightly above the posterior one which is also smaller, third eye similar in size to anterior one and placed clearly above the others.

Legs: Surfaces smooth, except for the external surface of femora which are granular. Basitarsi each with two well-developed pedal spurs, internal one 30% smaller than the external one in legs I and II, and symmetrical in legs III and IV. Telotarsi elongated and dorsoventrally compressed, distal lobe shallow and not projected ( Fig. 5C ), dorsally with a row of setae, ventrally each with a ventromedian row of poorly developed hyaline setae, and paired rows of ventrosubmedian setae. Telotarsus of leg III: Dorsal setae: 8–9 (N=15; median=8); ventrosubmedian prolateral setae: 6 in all studied specimens (N=15); ventrosubmedian retrolateral setae: 5–6 (N=15; median=6). Ungues shallowly curved and short, slightly asymmetrical in legs I and II being the retrolateral one smaller; equal in length in legs III and IV; telotarsus IV more elongated than the rest ( Fig. 5D ).

Pectines: Extremely large ( Fig. 5E ). Tooth count: 42–48 in males (N=5; median=43); 33–41 in females (N=10; median=33); first median lamella slightly more elongated in females than in males.

Sternum: With two conspicuous subtriangular lateral lobes, each with a stout macroseta.

Genital opercula: Subtriangular sclerites, with a convex retrolateral margin, quite similar in males and females, with five external setae.

Tergites: I–VI: With two anterior dorsosubmedian small setae, surface smooth in females, granular in the posterior and lateral margins in males; tergite VII: with two anterior dorsosubmedian setae, with two poorly developed dorsosubmedian carinae in posterior half of the segment, and two well-developed lateral carinae in posterior two thirds of the segment; surface smooth in the median dorsal area, densely granular in posterior two thirds, smooth below lateral carinae.

Sternites: Smooth surface in females, finely but densely granular in males; sternites III–VI with large elongated spiracles, and deep ventrosubmedian furrows.

Metasoma: Metasomal segment I dorsal surface poorly granular around median sulcus, the rest densely granular in males, slightly less granular in females; DL carinae granular but poorly developed, extending the entire length of the segment, with one median DL macroseta; lateral surface granular between DL and LM carinae, smooth between LM and LIM carinae; LM and LIM carinae only present in posterior two thirds of the segment; with one LM seta in the middle of the segment and one LIM macroseta in posterior third of the segment, ventrally without carinae, smooth in females, densely but finely granular in males, with 2-2 VL setae and two posterior VSM setae. Metasomal segments II and III similar to segment I but with LIM carinae less developed and restricted to the posterior margin. Metasomal segment IV dorsal surface smooth, DL carinae granular and extending the entire length of the segment, with two DL macrosetae, the posterior one slightly below the anterior one; lateral margins granular between DL and LM carinae; LM carinae extending the entire length of the segment but barely visible due to the granulation, with two LM macrosetae; LIM carinae absent; ventrally smooth in females, granular in males, with abundant ventral macrosetae: 37–46 (N=15; median=45), scattered and not forming clear rows. Metasomal segment V elongated; length/width ratio: 1.91 and 1.97 in both studied adult males, 1.97, 2.02 and 2.07 in three studied adult females; dorsal surface smooth, males with two relatively small glands or androvestigia placed in the anterior half of the segment, which are not longer than a quarter of the segment ( Fig. 5G ); DL carinae well developed and granular in males: extending the entire length of the segment, absent in females, with four to six DL macrosetae; lateral margins with a few scattered granules in females, densely granular between DL and LM carinae in males; LM carinae represented by scattered granules, and a row of six or seven setae in males, and only by the row of setae in females; area between LM and VL carinae smooth; ventral surface with scattered medium sized granules; VM carina barely visible, restricted to the basal third of the segment ( Fig. 5F ); with 20–24 scattered ventral macrosetae (N=15; median=21), that are not arranged in rows; VL carinae granular, straight, extending the entire length of the segment, but the basal most quarter is poorly developed, with 9 or 10 VL macrosetae (N=15; median=9).

Telson: Vesicle globose ( Fig. 5A ), slightly smaller in females ( Fig. 5B ); length/height ratio: 2.85 and 3.12 in both studied adult males; 2.82, 3.09 and 3.17 in three studied adult females; dorsolateral and ventral margins densely granular in males, smooth in females; ventrally with two shallow VSM furrows surrounding a barely visible VM carina, with four pairs of VSM and 3 pairs of VL macrosetae; laterally with a conspicuous furrow on each side; dorsal surface smooth and shallow, males with a conspicuous glandular subtriangular surface, partially but clearly subdivided in its posterior angle. Aculeus similar in size to the vesicle, shallowly curved in males ( Fig. 5A ), slightly less curved in females ( Figs. 5B ).

Hemispermatophore: Basal portion well developed. Distal lamina well developed, similar in length to the basal portion; apex gently inclined towards the internal margin ( Fig. 6B ), distal lobe (distal posterior flexure) medium sized, occupying less than a quarter of the distal lamina; distal crest medium sized, occupying the apical third of the distal lamina and without transverse crests, placed very close to the posterior margin and connected to the posterior margin of the distal lamina which is conspicuously thickened. Left hemispermatophore, cylindrical apophysis of the basal lobe well developed, being slightly wider in its median part, and with an acute and curved tip, barely reaching the base of the distal lobe, and slightly longer than the laminar apophysis ( Fig. 6A ); 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 or four chitinous crests. Right hemispermatophore without a cylindrical apophysis, but with a medium sized Internal Laminar Apophysis (ILA) poorly chitinized, and with continuous row of medium sized spines covering its anterior and dorsal margins; the rest as left hemispermatophore.

Distribution. Brachistosternus chimba n. sp. has only been collected in La Chimba National Reserve, an area belonging to the Chilean national system of protected areas (Corporación Nacional Forestal, CONAF). This reserve is adjacent to the city of Antofagasta, in northern Chile, and is placed in the Chilean Coast Range ( Fig. 1 ). Brachistosternus chimba n. sp. has been collected in the internal area of the reserve, in hilly areas ( Fig. 2E ), and in the external eastern part of the reserve, in a plain and open areas ( Fig. 2F ).

Ecology. La Chimba reserve, where B. chimba n. sp. has been collected, derives its name from La Chimba ravine, an arheic micro-basin with a surface area of 1,455.2 ha, and a drainage system composed of a third-order main ravine (La Chimba ravine) and the secondary ravines Guanaco and Los Cactus. These ravines are important biological relicts of the coastal desert of northern Chile (CONAF 1995). The vegetation in the area consists of an extremely xeromorphic open coastal desert shrubland dominated by cacti and succulents, e.g., Eulychnia iquiquensis (K. Schum.) Britton & Rose 1920 , Atriplex clivicola I.M. Johnst 1929 , Frankenia chilensis C. Presl ex Schult. & Schult. f. 1830, Nolana lachimbensis Dillon, Arancio & Luebert 2007 , Ophryosporus triangularis Meyen 1834 , and Tetragonia angustifolia Barnéoud 1847 ( Luebert & Pliscoff 2006). The reserve’s geomorphology is complex and is dominated by a highly degraded landscape with a broken topography, formed as a result of the pluvial-fluvial action resulting from a wetter past climate (CONAF 1995).

Brachistosternus chimba n. sp. is remarkable among genus Brachistosternus because we collected it mostly over rocks, and only occasionally we have found it wandering in the loose soil as most species of Brachistosternus do ( Ojanguren-Affilastro & Ramírez 2009); up to now this microhabitat preference has only been observed in Brachistosternus anandrovestigia Ojanguren-Affilastro, Pizarro-Araya & Ochoa 2018 (J. Ochoa pers. com.). The elongated and shallow shape of the telotarsi of B. chimba n. sp., with a particularly blunt anterior margin, ( Figs. 4C, D ) could be related with the kind of microhabitat used by this species.

All known specimens of B. chimba n. sp. have been collected in summer, which suggests that this species has a spring-summer activity period, as all known Brachistosternus species of the Atacama Desert.

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 3A–D. Brachistosternus chimba n. sp., habitus. A. Male, dorsal aspect; B. Male, ventral aspect; C. Female, dorsal aspect; D. Female, ventral aspect. Scale bars: 1 cm.

FIGURES 4A–G. Brachistosternus chimba n. sp. A. Right pedipalp chela, male, internal aspect; B. Right pedipalp chela, male, dorsal aspect; C. Right pedipalp chela, male, external aspect; D. Right pedipalp chela, male, ventral aspect; E. Right pedipalp chela, female, internal aspect; F. Right pedipalp patella, male, external aspect. G. Right pedipalp femur, male, dorsal aspect. White circles mark the position of each trichobothrium. Scale bars: 1mm.

FIGURES 5A–G. Brachistosternus chimba n. sp. A. Telson, male, lateral aspect; B. Telson, female, lateral aspect; C. Telotarsus III, internal margin; D. Telotarsus IV, internal margin; E. Right pecten, male, ventral aspect; F. Metasomal segment V, male, ventral aspect; G. Metasomal segment V, male, dorsal aspect. Scale bars: 1mm.

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.