Brachistosternus diaguita, Ojanguren-Affilastro & Ceccarelli & Mattoni & Salas & Iuri & Ochoa & Barrios, 2023

Ojanguren-Affilastro, Andrés A., Ceccarelli, F. Sara, Mattoni, Camilo I., Salas, Liliana, Iuri, Hernán, Ochoa, José A. & Barrios, Alexis, 2023, On the southernmost high Andean scorpion species, with the identification of a cryptic new species of Brachistosternus (Bothriuridae) through morphology, molecular data and species distribution models, Zoologischer Anzeiger 302, pp. 248-259 : 252-257

3.3.1. Brachistosternus diaguita n. sp. Ojanguren-Affilastro

( Fig. 1B , 2–8 ; Tables 1 , 3 and 4 )

Zoobank registration: http://zoobank.org/ urn:lsid:zoobank.org:act:9C97F796-07E4-439C-AE0C-6476C443DB8B .

3.3.1.1. Synonymic list: Brachistosternus aff. montanus : Ojanguren-Affilastro 2003: 33 (part.); Ojanguren-Affilastro 2005: 153. Brachistosternus montanus : Ojanguren-Affilastro 2005: 150, 153 (part); Ojanguren-Affilastro 2013: 39, 53 (part); Ochoa et al., 2011: 10 (part), 48; Ojanguren-Affilastro et al., 2016: 161, 164, 165, 166 (part); Ceccarelli et al., 2016: 5, 8, 9 (part).

3.3.1.2. Etymology. The specific epithet diaguita refers to the Diaguita district of the High Andean (“Altoandina”) biogeographic province as defined by Arana et al. (2021), from which this new species seems to be endemic. This name originally refers to the Diaguita people, a Quechua name given by the Incas, and posteriorly by the Spaniards, to the original pre-Inca native people from northwestern Argentina and northeastern Chile who spoke the Kakan language.

3.3.1.3. Diagnosis. Brachistosternus diaguita n. sp. is most closely related to B. montanus from central Argentinean Andes ( Fig. 8 ). Both species share a similar external morphology, pigment pattern, and hemispermatophore shape. Most specimens can be separated by the development of the pedipalp chela, which is slightly more robust in B. diaguita n. sp. ( Table 3 ). Additionally, dorsolateral setae of metasomal segment V are usually more developed in B. montanus , with two or three dorsolateral macrosetae on each side ( Fig. 6E ), whereas in B. diaguita n. sp. there is usually only one, or two microsetae ( Fig. 6B ), with only about ten percent of the specimens presenting one or two macrosetae.

Another very close species to B. diaguita is B. intermedius , from northern Argentina and Bolivia, this species can be easily separated by having a wider chela ( Fig. 6A ) and a more robust metasomal segment V ( Fig. 6D ) ( Table 3 ). Additionally, this species presents fewer ventral setae on metasomal segment V, with four basal, two median, and two posterior setae (4-2-2) ( Fig. 6D ), whereas B. diaguita n. sp. usually presents four basal, four median, two postero-median, and two median setae (4-4-2-2) ( Fig. 6A ).

3.3.1.4. Description: Based on the holotype male (MACN) and paratypes (MACN). Total length, males: 48–57 mm (N =15; mean = 51.65 mm); females: 49–61 mm (N =15; mean = 53.69 mm). (Measurements of male holotype and a female paratype in Table 4 ). Colour: Base colour dark yellowish, with dark brown pigmentation pattern in pedipalps, carapace, tergites, metasoma and legs; the remaining yellowish without dark spots ( Fig. 1B , 4A–D ). Chelicerae with faint reticulate pigmentation on external surface of manus, densely pigmented in the base of the fixed finger, and in the articulation with the movable finger, slightly pigmented in the external surface of movable finger. Carapace, with a heavily pigmented anterior triangular area from the area posterior to the ocular tubercle to the lateral ocelli; median ocular tubercle dark brown; with a reticular pigment pattern from the lateral margins to the postocular furrow, with two posterolateral dark spots covering most of posterior margin, leaving a median unpigmented area. Pedipalps, coxae and trochanter barely pigmented in the dorsal margin and near the articulation; femur with a well-developed stripe along DI margin, dorsally heavily pigmented in the distal half, anterior and posterior margins with faint reticular pigment, ventrally unpigmented. Patella, with dorso-internal, external and ventro-external stripes, connected to each other by reticulate pattern; internal surface heavily pigmented in the upper half, ventral surface unpigmented. Chela with six dark stripes along DI, DM, DS, D, E, and V carinae, these stripes are connected by a dense reticulate pattern, especially in the external surface; area near articulation of fixed and movable fingers with, barely visible, faint pigmentation. Legs: coxae unpigmented, trochanters barely pigmented in dorsal margin; femur and patella pigmented on the internal and external margins; tibia, basitarsi, and telotarsi unpigmented. Tergites I-VI heavily pigmented, each with three spots connected to each other, a median spot and two lateral spots, forming a sort of incontiguous single transversal stripe; tergite VII with three spots, one median anterior and two posterolateral, connected to each other. Sternites, sternum, genital opercula and pectines unpigmented. Metasomal segments I-III: dorsal surface with two posterolateral dark spots and an anterior median spot, connected to each other by reticular pigment pattern, lateral margins with a triangular pigmented area restricted by LSM and LIM carinae; ventral surface with three stripes, two VL and a VM, the VL stripes are always broad and well pigmented, whereas the VM stripe has a median thin well pigmented area and a more diffuse external area, this external area is wider in the anterior third of the segment usually joining with the lateral stripes, in more pigmented specimens it can also fuse with the VL stripes in the posterior margin, and in less pigmented specimens the VM stripe can be absent in segment I. Metasomal segment IV, dorsal surface as segments I– III, but the VM spot is longer and thinner reaching the last third of the segment, whereas the posterior spots are barely visible and can be absent in some specimens, lateral margins unpigmented, ventral margin with two VL and a VM stripe, all well developed, widening posteriorly and connecting to each other in the posterior third of the segment. Metasomal segment, V dorsal surface with an anterior median reticular area near the articulation, and with two posterior dark diffuse spots occupying the posterior third of the segment, Androvestigia of males light yellow, usually covered by whitish serum, lateral margins unpigmented; ventral margin with two wide VL stripes and a thin VM stripe, fusing to each other in the posterior margin, but also connecting to each other almost in the whole segment by reticulate pattern. Telson , vesicle with faint reticular pattern, except for paired, narrow VSM and L unpigmented stripes, corresponding to furrows; males with an unpigmented gland in the median area of dorsal surface; aculeus basally unpigmented, apex dark brown. Chelicerae: anterior margin of movable finger strongly curved; with two vestigial subdistal teeth. Pedipalps: Femur ( Fig. 5H ) with DI, DE, and VI carinae granular, extending the entire length of the segment; DE carina with two macrosetae, DI carina with one median macroseta, VE carina not conspicuous; anterior margin with some scattered coarse granules and two macrosetae; rest of the intercarinal surfaces smooth. Patella with DI and VI carinae slightly granular, more so in males, extending the entire length of segment ( Fig. 5G ); rest of the segment smooth. Chela manus medium sized ( Fig. 5B–F ), slightly more robust in males, length/width ratio, males 3.64–4.03 (N = 10; mean = 3.86), females 4.07–5 (N = 10; mean = 4.29), length/height ratio males 3.64–4.03 (N = 10; mean = 3.86), females 3.33–3.55 (N =10; mean =3.41); with a blunt V accessory carina, more conspicuous in males, internal surface with a pronounced, subtriangular projection near the articulation of the movable finger in males, absent in females; fingers elongated, with a median row of denticles, and with six or seven pairs of accessory denticles, the basal external accessory 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) associated with d and i; patella, with 19 trichobothria (2 d, i, 3 et, est, 2 em, 2 esb, 5 eb, 3 V); chela with 27 trichobothria (Dt, Db, 5 Et, Est, Esb, 3 Eb, dt, dst, dsb, db, et, est, esb, eb, ib, it, 5 V), Esb forming triangle with Eb2 and Eb3. Carapace: anterior margin convex, with four setae and a weak median projection. Surface slightly granular in the median area; lateral and posterior surfaces more densely granular. Anterior longitudinal sulcus, posterior longitudinal sulcus and lateral sulci very well developed. Median ocular tubercle well developed, placed slightly ahead the middle of the carapace, smooth surface except for its posterior margin which is slightly granular and bears two microsetae, one behind each eye, interocular sulcus deeply marked, median ocelli medium sized, ca. two diameters apart, and aiming laterally. Lateral ocelli pattern type 3A; with three small lateral ocelli on each side of carapace, being the median ocellus slightly smaller than the rest of the ocelli; anterior and posterior situated in the same horizontal axis, median ocellus situated one diameter below the rest. Legs: Surfaces smooth, except for the ventral surface of femorae in males which is slightly granular, less so in leg IV. Basitarsi each with two well developed, pedal spurs, being the external one about half of the size respect to the internal one in leg I, 30% percent smaller in leg II, and similar in size in legs IV and V. Telotarsi ventrolaterally compressed, tall and comparatively short, dorsally with a row of setae, ventrally each with a ventromedian row of poorly developed hyaline setae, and paired rows of ventrosubmedian setae; telotarsus III with following counts of setae: dorsal setae: 9–12 (N =15; median =11); ventro internal setae: 5–7 (N = 15; median = 6); ventro external setae: 5–6 (N = 15; median = 6). Ungues slightly curved, external ungues being about 30 percent smaller respect to the internal in legs I and II, and being equal in size in legs III and IV. Pseudoniquium and distal projection poorly developed. Pectines: Well developed. Tooth count, males: 27–32 (N = 15; median = 30); females: 23–29 (N = 15; median = 26). Sternum: With two small subtriangular lateral lobes, each with a macroseta slightly thicker and blunter than remaining ventral macrosetae ( Ojanguren-Affilastro et al., 2018). Genital opercula: Sclerites subtriangular, with a posterior lobe. Tergites: I–VI, with two anterior dorsosubmedian setae; surfaces, smooth in females, barely granular in the posterior third of the segment in males; VII granular in the posterior half, with paired lateral carinae in posterior two-thirds of segment, and paired submedian carinae restricted to the posterior margin, with two barely visible submedian keels in the median third of the segment, intercarinal surfaces with medium-sized granules, remainder of the surface finely granular. Sternites: Surface densely granular, especially in the median area, more so in males than in females, III–VI with large and elongated spiracles and small and deep ventrosubmedian furrows, VII with paired lateral macrosetae placed in conspicuous smooth pits. Metasoma: Metasomal segment I, dorsal surface barely granular, medium sulcus well developed and smooth; DL carinae poorly developed, granular, extending only in the posterior half of the segment, without a DL macrosetae; lateral surface granular between LM and DL carinae, the rest smooth, LM carinae granular, restricted to the posterior half of the segment, with a medial seta, LIM carinae poorly granular and only present in the posterior third of the segment, with a seta near the posterior margin; ventral surface smooth in females, granular in males, VL carinae complete but not granular, only represented by an elevation of the tegument, with two VL macosetae on each side in smooth pits in males, and with two VSM posterior macrosetae. Metasomal segments II and III similar to segment I but less granular and with less developed carinae, in some specimens with a small median DL setae, and ventrally with four additional VSM setae. Metasomal segment IV, dorsal surface granular, DL carinae barely visible, but occupying almost the entire length of the segment, with a DL seta in most specimens, lateral margins smooth in females, barely granular in males, with a pair of LSM setae, ventrally smooth, with abundant scattered macrosetae. Metasomal segment V, elongated ( Fig. 6A, B, C ); length/width ratio males 1.70–1.81 (N = 15, mean = 1.81), females 1.63–1.86 in (N = 15, mean = 1.74); dorsal surface smooth, Androvestigia of males very conspicuous, occupying more than a half of the dorsal surface of the segment ( Fig. 6B and C ), without a conspicuous DL carinae, reduced to some scattered granules in males, usually with a small DL setae that can be absent, but in some specimens there are one or two macrosetae, lateral margins granular between LSM and DL carinae in males, smooth in females, LSM carinae reduced to a row of four to six setae, ventral surface densely granular, more so in males, VL carinae well developed, granular and extending the entire length of the segment, VM carina as a granular elevation of the segment extending almost the entire length of the segment, being wider in the posterior third ( Fig. 6A ), with 8–9 VL macrosetae (N =15; Median =8), and abundant ventral macrosetae, usually arranged in four transversal rows, two in the anterior half of four to six macrosetae each, and two placed posteriorly, of one to three macrosetae each (more usually two), being the more common distribution 4-4-2-2 or 5-4-2-2; in some specimens there is an additional posterior row of one or two macrosetae. Telson : Vesicle globose, smaller in females, males with more protruding dorsal and ventral posterior margins; lateral and ventral margins granular in males, smooth in females; ventrally with two VSM smooth furrows, laterally with two longitudinal wide smooth furrows, males with a very conspicuous dorsal glandular area which occupies most of the dorsal margin ( Fig. 7A ). Aculeus longer than the vesicle, shallowly curved; more so in females ( Fig. 7B and C ). Hemispermatophore: Basal Portion well developed. Distal Lamina well developed, only slightly curved medially ( Fig. 7D, E, F ), 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. 7E ), of a similar thickness in most of its length with a curved acute tip barely reaching the base of the distal lobe, 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 medium sized Internal Laminar Apophysis (ILA) ( Ojanguren-Affilastro et al., 2018), poorly chitinized, with spines in its dorsal and external margins ( Fig. 7F ), apical spines of the row of spines longer than basal ones; the rest as left hemispermatophore.

3.3.1.4. Distribution. Brachistosternus diaguita n. sp. occurs at high altitudes, between 3200 and 4100 m asl., in central western Argentinean Andes, in northern San Juan, La Rioja and south-central Catamarca provinces ( Fig. 8 ). Its presence in the Famatina mountain chain, even if possible due to the environmental characteristics of the area, is based on a single record and therefore needs confirmation.

3.3.1.5. Ecology. The area where B. diaguita n. sp. has been collected belongs to the Diaguita district of high Andean biogeographic province as defined by Arana et al. (2021) ( Fig. 8 ). All specimens were collected in areas of shrub steppes with loose soil, being particularly abundant in the surroundings of Andean wetlands (“Mallines” in Spanish).

Brachistosternus diaguita n. sp. has been collected in sympatry with Orobothriurus compagnuccii Ochoa, Ojanguren-Affilastro, Mattoni & Prendini, 2011 , in the area of Laguna Brava, in La Rioja Province, whereas in the path to San Francisco international Pass in Catamarca province, it has been collected in sympatry with Bothriurus olaen Acosta 1997 , but only in lower altitudes (around 3200–3300 m asl.).

3.3.1.6. Type material. Holotype male, ARGENTINA, Catamarca Province, San Francisco international path , around a highland wetland (“Mallín”), 27 Ǫ 13 ′ 47.885 ′′ S, 68 Ǫ 6 ′ 22.993 ′′ W, 3715 m, Ojanguren-Affilastro, Barrios-Montivero, Iuri, Magalhaes & Piancentini coll. II/ 2022 ( MACN-Ar 42875 ) . Paratypes, same data as holotype, 5 males, 8 females, 13 juveniles .

3.3.1.7. Other studied material. ARGENTINA, Catamarca Province, San Francisco international path , Cortaderas , 27 Ǫ 43 ′ 62.49 ′′ S 68 Ǫ 13 ′ 46.07 ′′ W, 3200 m asl., Ojanguren-Affilastro & Korob coll., 10/II/ 2003, 3 males, 3 females, 7 juveniles ; San Francisco international path , 26 Ǫ 54 ′ 46.7 ′′ S, 68 Ǫ 06 ′ 47.9 ′′ W, 4035 m, Ojanguren-Affilastro, Barrios-Montivero, Iuri, Magalhaes & Piancentini coll. II/2022, 2 females ; San Francisco international path , 26 Ǫ 54 ′ 49.6 ′′ S 68 Ǫ 07 ′ 52.2 ′′ W, 4028 m, same collectors and date, 1 juvenile; San Francisco international path, 27 Ǫ 20 ′ 10.8 ′′ S 68 Ǫ 08 ′ 05.4 ′′ W, 3682 m, same collectors and date, 2 females; San Francisco international path, 27 Ǫ 43 ′ 42.8 ′′ S, 68 Ǫ 08 ′ 02.7 ′′ W, 3178 m, same collectors and date, 3 juveniles . La Rioja Province, Road to Laguna Brava : 28 Ǫ 25 ′ 50.3 ′′ S 68 Ǫ 50 ′ 31.3 ′′ W, 3900 m, Ojanguren-Affilastro, Compagnucci, Piacentini coll., 27/I/2006, 5 males, 12 females, 26 juveniles; Road to Laguna Brava, 28 Ǫ 31 ′ 31.80 ′′ S 68 Ǫ 46 ′ 15.99 ′′ W, 3150 m, Ojanguren-Affilastro & Korob coll., 4/III/ 2002, 1 male, 1 female, 1 juvenile ; Road to Laguna Brava , 28 Ǫ 32 ′ 18.6 ′′ S 68 Ǫ 45 ′ 11.9 ′′ W, 3200 m, same collectors and date, 2 males, 3 females, 2 juveniles ; Road to Laguna Brava , 28 Ǫ 27 ′ 17.2 ′′ S 68 Ǫ 50 ′ 39.9 ′′ W, 3835 m, same collectors and date, 1 male, 8 females, 7 juveniles ; Road to Laguna Brava , 3400 m 28 Ǫ 30 ′ 23.83 ′′ S 68 Ǫ 49 ′ 00.30 ′′ W, same collectors and date, 6 males, 2 females, 3 juveniles ; Road to Laguna Brava , “el Penon ˜” refuge, 28 Ǫ 30 ′ 26.50 ′′ S 68 Ǫ 47 ′ 57.00 ′′ W, 3600 m, Ojanguren-Affilastro & Piacentini, 25/I/2003, 6 males, 7 females, 20 juveniles ; Road to Laguna Brava , 28 Ǫ 31 ′ 56.44 ′′ S 68 Ǫ 45 ′ 45.60 ′′ W, 3100 m, same collectors and date, 7 males, 3 females ; Famatina, Road to La Mejicana gold mine, 28 Ǫ 55 ′ 31 ′′ S 67 Ǫ 40 ′ 23 ′′ W, 2845 m, Ojanguren-Affilastro, Compagnucci & Piacentini, 23/I/2006, 1 female . San Juan Province, San Guillermo, 29 Ǫ 9 ′ 51.69 ′′ S 69 Ǫ 21 ′ 30.32 ′′ W, 3700 m A. Reca coll., III-IV/1982, 1 male, 2 females, 3 juveniles ; Vega De Los Leones, 29 Ǫ 3 ′ 42.28 ′′ S 69 Ǫ 20 ′ 38.92 ′′ W, 3458 m, A. Reca coll., III-IV/1982, 1 female .

Figures

Fig. 1. A. Path to Paso San Francisco international pass, 3500 m asl, Catamarca, Argentina, type locality of Brachistosternus diaguita n. sp. B. Brachistosternus diaguita n. sp. female living specimen.

Fig. 2. A. Bayesian phylogeny of selected Brachistosternus species inferred using MrBayes. The values at the nodes are Bayesian posterior probabilities. The scale bar represents the branch lengths in substitutions per site. B. Bayesian species tree with nodeage estimates inferred using *BEAST. The values at the nodes are Bayesian posterior probabilities and the node bars represent the 95% highest posterior densities of the node age estimates. The scale axis is set to show Million years before present.

Fig. 3. Potential distribution of Brachistosternus species studied in this contributions A. Brachistosternus diaguita n. sp. B. Brachistosternus montanus. C. Brachistosternus intermedius. Warmer colors show areas with better predicted conditions. Black dots show the presence locations.

Fig. 4. Brachistosternus diaguita n. sp. habitus. A, B. Male. A. Dorsal aspect, B. Ventral aspect. C, D. Female, C. Dorsal aspect. D. Ventral aspect. Scale bar: 1 cm.

Fig. 5. A. Brachistosternus intermedius, pedipalp chela, male, internal aspect. B–H. Brachistosternus diaguita n. sp. B‒E. Pedipalp chela, male. B. internal aspect, C. dorsal aspect, D. external aspect, E. ventral aspect; F. Pedipalp chela, female, ventro-internal aspect. G. pedipalp patela, male, external aspect; H. pedipalp femur, male, dorsal aspect. Scale bars: 1 mm.

Fig. 6. A‒F. Metasomal segment V. A‒C. Brachistosternus diaguita n. sp., male. A. ventral aspect; B. dorso-external aspect, C. dorsal aspect; D. Brachistostenus intermedius, male, ventral aspect; E‒F. Brachistosternus montanus, male, E. dorsoexternal aspect, F. dorsal aspect. Scale bars: 1 mm.

Fig. 7. Brachistosternus diaguita n. sp., A‒C. Telson. a. male, dorsoexternal aspect; B. male, lateral aspect; C. female, lateral aspect; D‒F. Hemipermatophore. D. left hemispermatophore, external aspect; E. left hemispermatophore, internal aspect; F. right hemispermatophore, internal aspect. Scale bars: 1 mm.

Fig. 8. Map of central western Argentina showing the known distribution of Brachistosternus diaguita n. sp. (black circles), Brachistosternus montanus (black stars), and Brachistosternus intermedius (black triangles). The “Diaguita” district of the “Altoandina” biogeographical region is depicted in red, the “Cuyano” district of this region is depicted in blue, the “Puna” biogeographical region is depicted in orange, the “Prepuna” district of the “Monte” biogeographical region is depicted in green, and the Septentrional district of this region is depicted in turquoise.