Brachistosternus gayi, Ojanguren-Affilastro & Pizarro-Araya & Ochoa, 2018

Ojanguren-Affilastro, Andrés A., Pizarro-Araya, Jaime & Ochoa, José A., 2018, Five new scorpion species of genus Brachistosternus (Scorpiones: Bothriuridae) from the deserts of Chile and Peru, with comments about some poorly studied diagnostic characters of the genus, Zootaxa 4531 (2), pp. 151-194 : 153-162

Brachistosternus gayi n. sp.

( Figs. 1 , 2A , 3–6 ; Table 1 )

Type material. Holotype male: Chile, Coquimbo Region, road to Pascua Lama Mine (29°23'55.2'' S, 70°28'22.2'' W) , 3280 m asl, 6/ II /2014. A. A. Ojanguren-Affilastro, J. Pizarro-Araya, P. Agusto, R. Botero-Trujillo, H. Iuri ( MNHN); Paratypes (same data as holotype): 1 female ( MNHN) ; 1 male, 2 females, 3 juveniles ( MACN) ; Same road to Pascua Lama Mine, but at a lower altitude (3089 m asl), same date and collectors (29°26'42.4'' S, 70°30'6.7'' W); 2 males, 3 females ( MACN) ; Same road to Pascua Lama Mine, but at a lower altitude (3000 m asl), nearby a high altitude wetland (or “Bofedal”), same date and collectors (29°29'24.7'' S, 70°31'9.1'' W); 1 male, 1 female ( MZUC) ; 2 females, 4 juveniles ( LEULS) .

Etymology. This species is named after Claudio Gay Mouret (1800-1873), a French and Chilean naturalist, who deeply studied the flora, fauna, geology and geography of Chile, and who directed the Museo Nacional de Historia Natural in Santiago ( Chile), between 1830 and 1842.

Diagnosis. Brachistosternus gayi n. sp. is a member of the subgenus Brachistosternus because of the trichobothrial pattern and the shape of the hemispermatophore. It is a typical high Andean species of genus Brachistosternus , all of which share a very similar external morphology and a very similar hemispermatophore. Brachistosternus gayi n. sp. is the only known Andean species of the genus that presents paired VSM stripes in metasomal segments I-IV, which are fused proximally in segments II-IV ( Fig. 5E ), since the rest of the species of the genus bear a single VM stripe. This species occurs in sympatry with Brachistosternus perettii , also known from the Andes of Coquimbo region; both species can be separated not only by the pigment pattern of metasoma, but also because B. gayi n. sp. presents a VM carina in metasomal segment V ( Fig. 5B ), that is absent in B. perettii ; additionally, B. gayi n. sp. presents three dark spots in tergites I-VI, whereas B. perettii presents a single transverse stripe occupying almost the whole segment. Androvestigia of males are also slightly more developed in B. perettii than in B. gayi .

Another very closely related species from nearby Andean areas of Coquimbo Region is Brachistosternus coquimbo Ojanguren-Affilastro, Agusto, Pizarro-Araya & Mattoni 2007 . Both species can be separated by the pigment pattern of metasoma and because the telson of B. gayi n. sp. is lower and its aculeus less curved than in B. coquimbo . Length/height ratio of the telson in B. gayi n. sp. males: 3.19–3.42 (N=5; mean=3.32), in B. coquimbo males: 3.00–3.15 (N=6; mean=3.10); in B. gayi n. sp. females: 3.21–3.52 (N=5; mean=3.38), in B. Coquimbo females: 3.02–3.17 (N=3; mean=3.08).

Description. Based on the holotype male (MNHN) and paratypes (MACN, LEULS, MZUC). Total length: 60– 73 mm in males (N=6; mean= 65.5mm); 59–61 mm in females (N=4; mean= 60.25mm). Colour: Base colour dark yellowish, with dark brown, almost black, pigmentation pattern in carapace, tergites, metasoma and legs; the remaining yellowish without dark spots ( Figs. 3 A–D). Chelicerae with reticular pigmentation on the anterior margin of manus, and the external basal margin of the movable finger. Carapace, anterior margin with faint reticular pigment; with two broad dark stripes from the postocular furrow to the lateral ocelli, leaving a triangular unpigmented area in the anterior margin that does not reach the ocular tubercle nor the lateral eyes; ocular tubercle black; with two narrow lateral stripes and two small posterolateral dark spots. Tergites I–VI each with two well developed lateral dark spots, and a median small anterior dark subtriangular spot; these spots can be connected by faint reticulate pigment in the posterior margin; tergite VII with two posterolateral dark spots and a single anteromedian dark spot. Sternites, sternum, genital opercula and pectines unpigmented. Metasomal segments I-III: dorsal surface with two anterolateral little dark spots in the articulation, and two posterolateral dark spots occupying the posterior third of the segment, some specimens also present a little median reticular spot; lateral surfaces unpigmented; ventral surface with two VL stripes and two VSM stripes ( Fig. 5E ), VL and VSM stripes fused in the anterior margin of the segment, VSM stripes fused to each other in the posterior margin, in some specimens ventral stripes of segment I and II faint, or even absent. Metasomal segment IV: similar to segment III but ventral stripes more densely pigmented and dorsal spots more reduced. Metasomal segment V: dorsally with two posterolateral faint spots, that in some specimens are absent, males with paired median unpigmented glands; laterally with a faint median stripe, or unpigmented; ventrally posterior three quarters of the segment with two broad and well marked VL stripes, formed by the fusion of VL and VSM stripes, with a VM thin and faint reticular stripe in the anterior half of the segment, that can be absent in some specimens. Telson , vesicle with faint reticular pigment ventrally, and in some specimens also dorsally; aculeus dark brown. Pedipalps: trochanter unpigmented; femur with well developed stripes along DI, DE, and VE margins, with the dorsal stripes joining in a dorsal spot occupying almost half of the dorsal surface near the articulation with patella. Patella with dorsointernal and dorsoexternal stripes connected to each other by reticulate pattern on the dorsal surface; internal, external and ventral surfaces unpigmented. Chela with seven dark stripes along DI, DM, DS, D, E, V and VM carinae, in some specimens these stripes are connected by a faint reticulate pattern, specially in the external surface; area near articulation of fixed and movable fingers, and base of fingers unpigmented. Legs: coxae and trochanters unpigmented; femora densely pigmented along external margin, particularly near articulation with patella, slightly pigmented in the internal margin; patellae pigmented along ventrointernal margin, and slightly pigmented in the internal margin; tibiae, basitarsi, and telotarsi unpigmented.

Chelicerae: anterior margin of movable finger strongly curved in males, in an angle of about 90°, less curved in females; movable finger with two small subdistal teeth, the basalmost one bigger.

Pedipalps: Femur with DI and DE carinae formed by small scattered granules extending entire length of segment, with two DE macrosetae ( Fig. 4F ); VE carina formed by a slight elevation of the tegument; VI carina absent in females, formed by tiny sparse granules in males; anterior margin with few scattered medium sized granules and two macrosetae, one VI and one DI; posterior margin with 5 or 6 macrosetae arranged in two longitudinal rows, rest of the intercarinal surfaces smooth. Patella surfaces smooth, DI carinae only in males, formed by few scattered tiny granules ( Figs. 4G, H ); with one DI macroseta and three or four VI macrosetae. Chela manus slender, slightly more robust in males, length/width ratio, males: 4.25–4.56 (N=6; mean=4.46), females 4.45–4.66 (N=6; mean=4.56); the length/height ratio males: 3.32–3.42 (N=6; mean=3.48), females: 3.26–3.75 (N=6; mean=3.50); with blunt VM accessory carina, internal surface with slight bulge near articulation of movable finger (females), or with a pronounced, subtriangular projection (males; Figs 4-D ); fingers elongated, with a median row of denticles, and six or seven pairs of accessory denticles in fixed fingers, and seven or eight in movable fingers, basal external denticle is usually part of the median row ( Figs. 4 A–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 straight or slightly convex, with six setae and a well developed median projection. Surface: smooth in females; males with medium sized scattered granules except the median dorsal area that is smooth. Anterior longitudinal sulcus, posterior longitudinal sulcus, and lateral sulci present and well developed in males, less developed in females. Median ocular tubercle well developed, placed in the middle of the carapace, anterior margin elevates gradually, posterior margin ends abruptly (particularly in males), interocular sulcus shallow in males, absent in females, median ocelli small, 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 placed anteriorly, the anterior one slightly above the posterior one, third ocellus half of the size to the other two, and placed slightly above the others.

Legs: Surfaces smooth, except for the external surface of femur of leg IV which is slightly granular in males. Basitarsi each with two well developed pedal spurs, internal one 30% smaller than the external one in leg I, slightly smaller in leg II, and symmetrical in legs III and IV. Telotarsi tall and ventrolaterally compressed, 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: 11–13 (N=11; median=13); ventrosubmedian prolateral setae: 7–9 (N=11; median=8); ventrosubmedian retrolateral setae: 4–6 (N=11; 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, with slightly longer and less curved ungues and with a more developed distal projection.

Pectines: Tooth count: 31–34 in males (N=6; median=32); 25–30 in females (N=4; median=29); first median lamella more elongated in females than in males.

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

Genital opercula: Subtriangular sclerites, with a convex retrolateral margin, quite similar in males and females but slightly wider in males.

Tergites: I–VI: with two anterior dorsosubmedian setae, surface smooth in females, slightly granular in the posterior margin 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, granular in posterior two thirds, smooth below lateral carinae.

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

Metasoma: Metasomal segment I dorsal surface, smooth around median sulcus, the rest densely granular in males, slightly granular in females; DL carinae extending the entire length of the segment, granular and well developed in males, poorly developed in females, with one median DL macroseta; lateral surface granular between DL and LM carinae (more so in males), 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, granular in males, smooth in females, with 2-2 VL setae and two posterior VSM setae. Metasomal segments II and III similar to segment I but DL carinae absent in females, and LIM carinae less developed in females. Metasomal segment IV on females smooth and acarinate; on males dorsal surface smooth, DL carinae granular, 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 only present as a slight elevation of the tegument near the posterior margin of the segment, with two LIM macrosetae; ventrally smooth, VL and VSM macrosetae forming four rows of four setae each (arrangement: 4-4-4- 4). Metasomal segment V elongated; length/width ratio males: 1.81–2.01 (N=6; mean=1.93); females: 1.85–1.97 (N=5; mean=1.91); dorsal surface smooth, males with two medium sized, narrow glands or androvestigia placed in the median part of the segment ( Fig. 5A ); DL carinae, males: extending the entire length of the segment, represented by scattered, coarse granules and a row of four macrosetae; obsolete in females, only represented by the row of setae; lateral margins smooth in females, densely granular between DL and LM carinae in males; LM carinae represented by scattered granules, and a row of five or six 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 granular, straight, and extending the entire length of the segment ( Fig. 5B ); usually with four transverse rows of macrosetae, two near the anterior margin of four macrosetae, and two of two macrosetae each in the median part of the segment (distribution 4-4-2-2); VL carinae granular, straight, and extending the entire length of the segment, with 9 to 13 VL macrosetae (N=24; median=11).

Telson: Vesicle globose, slightly smaller in females; length/height ratio, males: 3.19–3.42 (N=5; mean=3.32); females 3.21–3.52 (N=5; mean=3.38); dorsolateral and ventral margins with blunt granules in males, smooth in females; ventrally with two shallow VSM furrows surrounding a VM carina, with four pairs of VSM and three 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 longer than the vesicle, shallowly curved in males, slightly less curved in females ( Figs. 5C, D ).

Hemispermatophore: Basal portion well developed. Distal lamina well developed, similar in length to the basal portion; apex gently inclined towards the internal margin ( Fig. 6A ), 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, 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. 6B ); 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 well developed formed by three or four chitinous crests. Right hemispermatophore without a cylindrical apophysis, with a medium sized ILA chitinized, and with medium sized spines in its anterior and dorsal margins ( Fig. 6C ); the rest as left hemispermatophore.

Distribution. Brachistosternus gayi n. sp. has only been collected in a narrow altitudinal range between 3000 and 3300 m asl, in the Chilean path ascending to the Pascua Lama Mine, in Atacama region, in northern Chile ( Fig. 1 ).

Ecology. The area where B. gayi n. sp. has been collected is a shrub steppe ( Fig. 2A ) that belongs to the Alto Andina Botanical region ( Gajardo 1993). This species has only been collected in sympatry with Brachistosternus perettii . The plant community of the area where B. gayi n. sp. has been collected includes Adesmia hystrix Phil. , Fabiana imbricata Ruiz & Pav. , Ephedra breana Phil. and shrubs of genus Haplopappus.

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

Figures

FIGURE 1. Distribution map of Brachistosternus gayi n. sp., Brachistosternus philippii n. sp., Brachistosternus contisuyu n. sp., Brachistosternus misti n. sp. and Brachistosternus anandrovestigia n. sp.

FIGURES 2A–F. Type locality of Brachistosternus species herein described. A. Brachistosternus gayi n. sp.; B. Brachistosternus philippii n. sp.; C. Brachistosternus contisuyu n. sp.; D, E. Brachistosternus misti n. sp.; F. Brachistosternus anandrovestigia n. sp.

FIGURES 3A–D. Brachistosternus gayi n. sp., habitus. A. Male, dorsal aspect; B. Male, ventral aspect (pectens of this male are naturally mutilated); C. Female, dorsal aspect; D. Female, ventral aspect. Scale bars: 1 cm.

FIGURES 4A–H. Brachistosternus gayi n. sp. A. Left pedipalp chela, male, internal aspect; B. Left pedipalp chela, male, ventral aspect; C. Left pedipalp chela, male, external aspect; D. Left pedipalp chela, male, dorsal aspect; E. Left pedipalp chela, female, internal aspect; F. Left pedipalp femur, male, dorsal aspect. G. Left pedipalp patella, male, external aspect; H. Left pedipalp patella, male, ventral aspect. Scale bars: 1mm.

FIGURES 5A–E. Brachistosternus gayi n. sp. A. Metasomal segment V, male, dorsal aspect; B. Metasomal segment V, male, ventral aspect; C. Telson, male, lateral aspect; D. Telson, female, lateral aspect; E. Metasomal segments I-V ventral aspect of the pigmentation pattern. Scale bars: 1mm.

FIGURES 6A–C. Brachistosternus gayi n. sp. A. Left hemispermatophore, external aspect. B. Left hemispermatophore, detail of the lobe region; C. Right hemispermatophore, detail of the lobe region. Scale bars: 1mm.

Tables

TABLE 1. Measurements (mm) of Brachistosternus gayi n. sp. (holotype and paratype, MNHN) and Brachistosternus philippii n. sp. (holotype and paratype, MNHN).

	Brachistosternus gayi n. sp.		Brachistosternus philippii n. sp.
	Male holotype	Female paratype	Male holotype	Female paratype
Total length	72.05	59.87	56.19	60.11
Carapace, length	9.29	7.68	6.38	6.62
Carapace, anterior width	6.38	4.85	4.12	4.44
Carapace, posterior width	9.80	7.43	6.46	7.27
Mesosoma, total length	17.60	17.93	14.99	22.00
Metasoma, total length	35.63	26.42	26.98	24.22
Metasomal segment I, length	5.66	4.44	4.2	4.04
Metasomal segment I, width	6.46	4.60	3.55	3.47
Metasomal segment I, height	5.66	3.64	3.15	2.83
Metasomal segment II, length	6.46	4.85	5.25	4.44
Metasomal segment II, width	5.98	4.20	3.23	3.15
Metasomal segment II, height	5.41	3.55	2.91	2.83
Metasomal segment III, length	7.03	5.01	5.41	4.75
Metasomal segment III, width	5.57	4.04	3.07	2.99
Metasomal segment III, height	5.01	3.47	2.75	2.75
Metasomal segment IV, length	7.43	5.49	6.06	5.17
Metasomal segment IV, width	5.09	3.55	2.99	2.83
Metasomal segment IV, height	4.44	3.07	2.67	2.66
Metasomal segment V, length	9.05	6.63	6.06	5.82
Metasomal segment V, width	4.93	3.47	2.99	2.99
Metasomal segment V, height	4.04	2.66	2.50	2.34
Telson , length	9.53	7.84	7.84	7.27
Vesicle,length	5.66	4.04	4.21	4.04
Vesicle, width	3.55	2.59	2.91	2.50
Vesicle, height	2.91	2.18	2.42	2.10
Aculeus, length	3.87	3.80	3.63	3.23
Femur, length	6.30	4.93	5.89	4.68
Femur, width	2.02	1.57	1.53	1.37
Patella, length	6.22	5.01	4.93	4.44
Patella, width	2.71	2.02	1.86	2.02
Chela, length	10.76	8.88	9.86	8.48
Chela, width	2.42	1.94	2.85	2.83
Chela, height	3.23	2.51	3.50	2.18
Movable finger, length	6.36	5.17	3.65	4.90