Loxosceles vallenar Brescovit, Taucare-Ríos, Magalhaes & Santos, 2017

Magalhaes, Ivan L. F., Iuri, Hernán A., Brescovit, Antonio D. & Pizarro-Araya, Jaime, 2024, The tiniest violin: the male of Loxosceles vallenar (Araneae, Sicariidae), ZooKeys 1206, pp. 327-346 : 327-346

Loxosceles vallenar Brescovit, Taucare-Ríos, Magalhaes & Santos, 2017

Figs 3 , 4 , 5 , 6 , 7 , 8

Loxosceles vallenar Brescovit, Taucare-Ríos, Magalhaes & Santos, 2017: 14, fig. 8 E.

Holotype (examined).

Chile • 1 ♀; Atacama, Prov. Huasco, Vallenar , 3 km S Vallenar; 460 m. a. s. l. [28.601 ° S, 70.77 ° W]; 7 Jan. 1985; N Platnick, O Francke leg.; deposited in AMNH.

New records.

Chile • 1 ♂; Atacama, Prov. Huasco, Boquerón Chañar; Algarrobal ; 992 m. a. s. l.; (28.3708 ° S, 70.4128 ° W); 24–25 Nov. 2022; J Pizarro-Araya, FM Alfaro, JE Barriga, AA Ojanguren-Affilastro, HA Iuri & JE Calderón leg.; IFM- 2580 ; MACN - Ar 44129 • 1 ♂; same collecting data; MACN - Ar 44130 • 1 ♀; same collecting data; MACN - Ar 44131 .

Remarks.

The genitalia of the holotype was incorrectly illustrated by Brescovit et al. (2017), as the digitiform, membranous median receptacles were overlooked. Re-examination of the holotype revealed they are present (Fig. 5 D ). We briefly describe the females collected with the males, especially their endogyne, which is in a better state than that of the holotype. The hitherto undescribed male has a palpal bulb bearing an embolic keel and overall morphology concordant with the spadicea species group (Figs 6 – 8 ). Thus, the species is moved from the laeta species group to the spadicea species group.

Diagnosis.

Males resemble those of other members of the spadicea species group by the subtriangular cymbium in dorsal view (Fig. 6 B ) and embolus bearing a keel (Fig. 7 C ), but can be distinguished by the clypeus bearing macrosetae (Figs 3 , 6 A – C ) (vs. clypeus without macrosetae) and by the more piriform, tapering copulatory bulb (Fig. 7 B ) (vs. bulb clearly globose; Gertsch 1967, figs 1, 4, 9). Females resemble those of other members of the spadicea species group by the short and digitiform median receptacle, but differ by the inwards curved base of the lateral receptacle (Fig. 5 ) (vs. base of the lateral receptacle sinuous to convoluted; Gertsch 1967, figs 11–14).

Description.

Male from Boquerón Chañar, Atacama, Chile ( MACN - Ar 44130). Coloration in ethanol (Fig. 6 A ). Carapace yellowish-brown with slightly darker pars cephalica, eyes surrounded by black pigment rings. Chelicerae orange brown. Labium light brown. Endites brownish-cream at base, darker at median third, whitish at tip. Palps yellowish-brown, tarsus darkest. Sternum brownish-cream. Legs uniformly light brown. Opisthosoma uniformly brownish-gray. Measurements. Total length 3.62. Carapace length 1.92, width 1.48. Clypeus height 0.23. Eye diameters and interdistances: ALE 0.11, PLE 0.12, PME 0.10, ALE – PME 0.13. Sternum length 1.13, width 0.95. Palp: femur length 1.08, height 0.18, tibia length 0.60, height 0.25, tarsus length 0.27. Leg I 8.6 (2.38, 0.58, 2.43, 2.38, 0.83). Leg II 10.11 (2.82, 0.59, 3.03, 2.84, 0.83). Leg III 7.53 (2.23, 0.57, 1.95, 2.14, 0.64). Leg IV 9.88 (2.82, 0.58, 2.75, 2.96, 0.77). Leg formula 2413. Abdomen: length 1.67, width 1.08. Femur I with ~ 17 prolateral macrosetae in a subdistal patch (Fig. 6 D ). Metatarsus I unmodified. Clypeus with ~ 20 macrosetae (Fig. 6 C ). Male genitalia (Figs 7 , 8 ). Palpal femur with 5 prolateral macrosetae in apical third, tibia slightly swollen, with two pronounced condyles apically, cymbium short and subtriangular in dorsal view, bulb short and rounded, embolus curved and tapering retrolaterally, with a prolateral keel, without micro-spines (Fig. 8 ). State of the specimen: good; left palp dissected.

Female from Boquerón Chañar, Atacama, Chile ( MACN - Ar 44131). Coloration and general structure as in the holotype (Fig. 4 ). Carapace length 2.20, width 1.68. Genital region externally pubescent but without stronger sclerotization (Fig. 4 E ). Endogyne (Fig. 5 ). Median receptacle digitiform, slightly sinuous and lightly sclerotized, bearing glandular pores throughout. Lateral receptacle with thin, sclerotized and arched base bearing glandular pores, leading to a rounded, unsclerotized head lacking pores; fold (presumably uterus externus and / or interpulmonary fold) short and membranous. State of the specimen: good; endogyne dissected.

Variation.

The two males and two females examined have seemingly identical genitalia. Two males: total length 3.62 to 3.74; carapace length 1.92 to 1.97; tibia I length 2.43 to 2.73. Both females have a carapace length of 2.2 and vary in total length from 5.53 to 6.00.

Natural history.

The label data indicates that the holotype was collected “ in scrubby mountain-side, under rocks ”. The specimens from Boquerón Chañar were collected at night, searching with headlights. The male specimens were actively walking on the ground.

Habitat.

Specimens of Loxosceles vallenar and L. vicentei were collected in vegetation zones characterized by an inland Mediterranean-desert shrubland of Adesmia argentea Meyen and Bulnesia chilensis Gay ( Luebert and Pliscoff 2006) . These areas are defined by an extremely open shrubland with tall shrubs and the presence of tree species. Shrubs include A. argentea , Bulnesia chilensis , Balsamocarpon brevifolium Clos , Cordia decandra Hook. & Arn. , Heliotropium sinuatum (Miers) I. M. Johnst. , Pintoa chilensis Gay , and Proustia ilicifolia Hook. & Arn. Additionally , low shrubs such as Caesalpinia angulata (Hook. & Arn.) Baill. , Encelia canescens Lam. , Pleurophora pungens D. Don , and cacti like Cumulopuntia sphaerica (C. F. Först.) E. F. Anderson and Trichocereus coquimbanus (Molina) Britton and Rose are common. Herbaceous plants abound during the rainy season, including species like Cruckshanksia pumila Clos and Argylia irradian (L.) D. Don. This entire environment is dominated by trees such as Neltuma chilensis (Molina) Hughes & Lewis , Geoffroea decorticans (Gillies ex Hook. & Arn.) Burkart , Acacia caven (Molina) Molina , and Schinus polygama (Cav.) Cabrera ( Luebert and Pliscoff 2006) (Fig. 1 ). The climate in the area is semiarid subtropical Mediterranean in the northern margin and marine subtropical Mediterranean in the southern margin ( Novoa and Villaseca 1989). The total precipitation recorded in the study area (Vallenar Station, 28 ° 33 ' 6.11 " S, 70 ° 47 ' 25.92 " W, 421 m. a. s. l.) in 2022 was 83.8 mm and was concentrated in July (66.5 mm) and June (4.9 mm) ( CEAZA-Met 2024).

Distribution.

Originally described from Vallenar, the new record extends the distribution of the species about 40 km northeastward. Both points are in Huasco Province, Atacama region, Chile (Fig. 2 ).

Figures

Figure 1. Habitat in Boquerón Chañar, Atacama, where Loxosceles vallenar and L. vicentei were collected.

Figure 2. Distribution of Loxosceles vallenar and Loxosceles vicentei. The star represents a new record for both species in the same locality.

Figure 3. Loxosceles vallenar, live male specimen from Boquerón Chañar A entire specimen B close-up. Notice the clypeal setae. Scale bar: 1 mm.

Figure 4. Loxosceles vallenar Brescovit, Taucare-Ríos, Magalhaes & Santos, females A holotype from Vallenar (AMNH), dorsal B – E female from Boquerón Chañar (MACN - Ar 44131) B dorsal C carapace, anterior D abdomen, ventral E genital region, ventral. Scale bars: 1000 µm (A); 500 µm (B – D); 200 µm (E).

Figure 5. Loxosceles vallenar, median and lateral receptacles of the female genitalia A – C female from Boquerón Chañar (MACN - Ar 44131) D holotype from Vallenar (AMNH). Abbreviations: IF? = putative interpulmonary fold, LR = lateral receptacle, MR = median receptacle, UE? = putative uterus externus; details could not be resolved in light microscopy. Scale bars: 200 µm (A, C, D); 50 µm (B).

Figure 6. Loxosceles vallenar, male from Boquerón Chañar (MACN - Ar 44130) A habitus, dorsal B clypeus, anterior C clypeus, dorsal D left femur I, prolateral. Scale bars: 1000 µm (A); 500 µm (B, D); 200 µm (C).

Figure 7. Loxosceles vallenar, males from Boquerón Chañar (MACN - Ar 44130) (except B, MACN - Ar 44129, dry specimen before sputter-coating), left palps A, B prolateral C dorsal D retrolateral. Arrows indicate embolic keel. Scale bars: 200 µm (B – D to the same scale).

Figure 8. Loxosceles vallenar, male left palp (MACN - Ar 44129) under scanning electron microscopy A prolateral B bulb, prolateral C detail of embolic keel D bulb, apical E bulb, dorsal F bulb, retrolateral. Arrows indicate embolic keel. Scale bars: 200 µm (A); 100 µm (B, E, F); 50 µm (C).