On Chilean Loxosceles ( Araneae : Sicariidae ) : first description of the males of L . surca and L . coquimbo , new records of L . laeta and three remarkable new species from coastal deserts

Loxosceles Heineken & Lowe, 1832 spiders are infamous for their medical importance, but a taxonomic picture of the genus is still far from complete. In this study, the Chilean species of Loxosceles are described and mapped. The males of Loxosceles surca Gertsch, 1967 and L. coquimbo Gertsch, 1967 are described for the first time. Three new species with narrow distributions are described from central and northern Chile: Loxosceles diaguita sp. nov. from the Antofagasta Region, L. pallalla sp. nov. from Coquimbo and L. vallenar sp. nov. from Atacama. The first two species are remarkable in their morphology and do not fit into any of Gertsch’s species groups, suggesting that Chile still harbours an undiscovered phylogenetic diversity of the genus. New distribution records for Loxosceles laeta (Nicolet, 1849) are provided throughout Chile.


Introduction
The spider genus Loxosceles Heineken & Lowe, 1832 is well-known for the dermonecrotic effects of their venom (Vetter 2008;Silva et al. 2004), fi guring among the most frequent agents of arachnid envenomation in South America (Silva et al. 2015). The genus currently contains 116 species distributed mostly in the USA, Mexico, the Caribbean and South America. A few species have been described or reported from the African mainland, the Canary Islands and China, and at least two species are widespread and synanthropic (World Spider Catalog 2017). Considering its importance as an agent of envenomation and the biotechnological interest on its toxins (Senff-Ribeiro et al. 2008), one could imagine the genus is particularly well known taxonomically. However, the systematics of the genus is still problematic in most of its distribution range. This is particularly true regarding the South American fauna, which contains a third of the species of the genus (World Spider Catalog 2017).
The most recent revision of the South American Loxosceles was published 50 years ago (Gertsch 1967). Nevertheless, this study is still relevant for species recognition in the region due to the quality of its illustrations and detailed descriptions. However, most species included in Gertsch's revision remain poorly known regarding both its morphology and geographic distribution. This situation is well illustrated by the Chilean species of the genus. The fi rst species described for the country, Loxosceles laeta (Nicolet, 1849) is well known for its current widespread distribution (Gertsch 1967;World Spider Catalog 2017), its association with domestic habitats (Schenone et al. 1970;Fischer et al. 2011;Taucare-Ríos et al. 2013) and, as a consequence, for being responsible for most dermonecrotic arachnid envenomation accidents in South America (Schenone et al. 1989;Schenone 2004). On the other hand, two other species recorded in the country are known only from a few taxonomic reports. Loxosceles coquimbo Gertsch, 1967 is known only from the type locality and has never been reported again in the literature after its original description (Gertsch 1967;World Spider Catalog 2017). Most recently, Loxosceles surca Gertsch, 1967, a species described from two nearby localities in Peru only, has been recorded from northern Chile (Taucare-Ríos 2011). Considering the well-recognized sampling defi ciencies on South American spiders, it is open to speculation whether these species are truly short-range endemics or whether they have not been recorded of their entire distribution area. Additionally, both species are known so far only from the females, which might hamper their identifi cation.
In this study, we contribute to the advancement of the knowledge on the Chilean Loxosceles by describing the males of L. coquimbo and L. surca. We also complement the known distribution of L. laeta by providing new records. Most remarkably, we describe three new short-ranged species, a demonstration that the small number of species of the genus in the country is a result of sampling defi ciency and lack of taxonomic studies in this group.

Methodology
Terminology, format of descriptions and leg spination follow Sánchez-Ruiz & Brescovit (2013). All measurements are in millimetres. Digital multifocus photos were taken using a Leica DFC 500 digital camera attached to a Leica MZ16A stereo microscope and a Leica M165C stereo microscope. The photographs were assembled using the software Leica Application Suite Version 3.3.0 and Helicon Focus 6 (available from http://www.heliconsoft.com/heliconsoft-products/helicon-focus/). SEM images were taken with a FEI Quanta 250 Scanning Electron Microscope at the Instituto Butantan. After dissection, female genitalia were placed in clove oil, examined and illustrated using a Leica MZ12 stereo microscope with a drawing tube. Geographic coordinates were obtained using a GPS for specimens collected by us, or through information on museum specimen original labels. Localities from museum samples without coordinates were georeferenced using Google Earth®.

Diagnosis
Loxosceles laeta could be confused in Chile only with the sympatric L. surca. It is easily distinguished from L. surca by the anterior border of the carapace not too hirsute, the male palp with tibia medially incrassate and four times longer than the cymbium (Fig. 1A). The female internal genitalia are very similar to those of L. surca, but can be recognized by the transverse enlargement at the base of the tubular receptacle, which is usually angled or produced into a distinct tubercle or short blind, fi nger-like projection (see Gertsch 1967: pl. 6, fi gs 3-4, 6-9).

Description
Male and female Described by Gertsch (1967).

Note
Males and females were collected next to each other in at least three different localities.

Diagnosis
Loxosceles surca could be confused in Chile only with the sympatric L. laeta. It is distinguished from L. laeta by the anterior border of the carapace very hirsute, the male palp with tibia narrowed medially, with a dorsal concavity, and fi ve times longer than the cymbium ( Fig. 1B-C). The female internal genitalia are very similar to those of L. laeta, but can be distinguished by the almost absent transverse enlargement at the base of the tubular receptacles (Fig. 8A).

Note
Males were not collected with females; the only male comes from a locality 83 km to the north of the nearest collected female. They are here associated based on the morphology of genital and copulatory organs, which are comparatively simple in the male and the female, and fi tting the diagnosis of the laeta species-group, as well as on the leg formula (4213). Despite having visited the type locality, we could not obtain any topotypes.

Diagnosis
Loxosceles coquimbo differs from other Chilean species by the male palp with tegulum globose and embolus short and sinuous at tip ( Fig. 2A-B). Females can be recognised by the inner and outer spermathecae with nearly the same size (

Distribution
Known from the Coquimbo Region in Chile only (Fig. 10).

Diagnosis
Males are easily distinguished from other Neotropical Loxosceles by the shape of the palpal bulb, with a large embolus sided by a keel with several longitudinal grooves (Figs 3C-D, 6A-C). Females are distinguished by the robust, S-shaped stalks of the outer spermathecae and by the reduced inner spermathecae with long, thin stalks (Fig. 8D).

Etymology
The Diaguitas are a Native American tribe whose original territory covered northwestern Argentina and northern Chile, including portions of the Antofagasta Region, the type locality of the species. The name is to be treated as a noun in apposition.

Males and females
Males and females have been matched because they have been collected in the same locality in two different expeditions.

Diagnosis
Loxosceles pallalla sp. nov. can be distinguished from all Loxosceles species by the small tegular base and extremely long embolus with a fl attened keel in the male palp (Fig. 7). Females can be recognised by the spermathecae with two receptacles originating from the same short and curved stalk, and the inner spermathecae larger than the outer one (Fig. 8C).

Etymology
The specifi c epithet means "fl at" in the Aymara language, and refers to the fl attened embolus of this species.

Note
Males and females were matched because they have the same coloration and have leg formula 2413. Also, both males and females have a deviant genital morphology, not fi tting in any of Gertch's speciesgroups. Although this species may be sympatric with Loxosceles coquimbo, the latter are easily separated by the leg formula 4213.

Distribution
Known only from the Coquimbo Region, Chile (Fig. 10).

Diagnosis
Females of Loxosceles vallenar sp. nov. can be distinguished from other Chilean species by the spermathecae with large base and slender, curved receptacles (Fig. 8E).

Etymology
The specifi c name is a noun in apposition taken from the type locality.

Distribution
Known only from the type locality in the Atacama Region, Chile (Fig. 10).

Discussion
Relationships Gertsch (1967) proposed the gaucho, spadicea, amazonica and laeta groups in the genus Loxosceles. These morphological groups are still accepted and have so far resisted scrutiny from molecular (Binford et al. 2008) and morphological (Magalhaes et al. 2017) phylogenetic analyses. The Chilean Loxosceles fauna was known only by two species (World Spider Catalog 2017) and is here expanded with records of L. surca and three new species, two of which cannot be unambiguously assigned to any of Gertch's groups.
Loxosceles laeta and L. surca are undoubtedly included in the laeta group by the original defi nition of Gertsch (1967), mainly based on the long palpal tibia and elongated embolus ( Fig. 1A-B, D). These characters are easily observed in the species of this group distributed in Ecuador, Peru, northern Chile and Argentina and southern Brazil. Loxosceles coquimbo was described based on a female and was included in the laeta group by Gertsch (1967) mainly based on the leg formula, the thickened pedipalp and, strangely, on the pair of tubular receptacles on each side of the transverse atrium (Fig. 8B). The genitalia of the females of the laeta-group are more variable than those of the males. The inclusion of Loxosceles coquimbo in the group seems reasonable with the discovery of the male, which has a long palpal tibia ( Fig. 2A-B).
Among the new species here described, Loxosceles vallenar sp. nov. could also be a member of the laeta-group, pending confi rmation upon discovery of the male. The female has the leg formula 4213 as well as tubular receptacles on each side of the elongated and transverse atrium, both are characteristics of this group (Fig. 8E).
Loxosceles diaguita sp. nov. shares two characters with the spadicea-group: the shape of the spermathecae (with inner spermathecae placed externally to the larger outer spermathecae; compare with Magalhaes et al. 2017: fi g. 63C) and a keel in the embolus (Magalhaes et al. 2017: fi g. 63B). However, it does not have the typical, apomorphic morphology of the male bulb of this group (rather short and spherical), nor the much reduced inner spermathecae (see Gertsch 1967). This suggests that L. diaguita sp. nov. might represent the sister group of all other species in the spadicea-group. Curiously, it occurs west of the Andes, while all other species of the group occur east of this mountain range.
Finally, Loxosceles pallalla sp. nov. is the most peculiar of the herein described species, with a long and fl attened embolus originating from the retrolateral side of the bulb in the male palp (Fig. 7) and with female genitalia having two receptacles arising from a single stalk (Fig. 8C). Based on the male palp with a short cymbium and a relatively short and dilated tibia (Fig. 7A-B), and following Gertsch's (1967) classifi cation, this species should be included in the rufescens or gaucho-groups. However, the Fig. 10. Geographic distribution records of species of Loxosceles in Chile. Records of L. laeta (Nicolet, 1849) are based on the material examined in this study and on Gertsch (1967). Stars under L. surca Gertsch, 1967 andL. coquimbo Gertsch, 1967 are records from Gertsch (1967). female genital morphology is quite unmodifi ed, and does not resemble the highly apomorphic female morphology of any of these groups (with sclerotized plates in the gaucho-group, and with several apical lobes in the the rufescens-group, see Fukushima et al. 2017). Additionally, the keel in the male palp could be a shared feature between this species and the spadicea-group. It would be very interesting to include L. pallalla sp. nov. in a phylogenetic analysis to test its position in a quantitative way. At any rate, its discovery demonstrates that the Chilean fauna may still hold an undiscovered Loxosceles diversity.

Diversity
In this paper we recognize six species, three of them endemic to the Chilean transitional coastal desert. The transitional coastal desert of Chile (25-32º S) represents the northern limit of the biodiversity hotspot recognized for Central Chile (Gaston 2000), and is a major area of endemism for restrictedly distribute arthropods (Pizarro-Araya & Flores 2004;Cepeda-Pizarro et al. 2005;Agusto et al. 2006;Ojanguren-Affi lastro et al. 2007). The discovery of these new species confi rms the importance of this area for biological conservation (Cepeda-Pizarro et al. 2005). On the other hand, Loxosceles surca and L. vallenar sp. nov. are restricted to arid inland environments of northern and central Chile, respectively, while L. laeta is widely distributed and would be the only synanthropic species in the country (Taucare-Ríos et al. 2013).